59284471 Plumbing Systems Advanced

ADVANCED PLUMBING SYSTEMS

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136

Animal-careFacility PipingSystems

Continuing Education from Plumbing Systems & DesignKenneth G.Wentink, PE, CPD, and Robert D. Jackson

NOVEMBER/DECEMBER 2006

PSDMAGAZINE.ORG


INTRODUCTIONThis chapter discusses various piping systems uniquely associ-ated with the physical care, health, and well-being of labora-tory animals. Included are various utility systems for animal watering, water treatment, room and floor cleaning, equipment washing, cage flushing and drainage, and other specialized piping required for laboratory and experimental work within the facility. Other systems involved with general laboratory and facility work, such as those for compressed gases and plumbing, are discussed in their respective chapters.

GeNeRalIt is expected that a facility involved with long-term studies will have different operating and animal drinking-water qual-ity requirements than one used for medical research. For criti-cal studies, the various utility systems shall incorporate design features necessary to ensure reliability and provide a consistent environment. As many variables as are practical (or desirable) shall be eliminated to ensure the accuracy of the ongoing exper-iments being conducted. Regardless of the facility type, different users and owners have individual priorities based on experi-ences, operating philosophies, and corporate cultures that must be established prior to the start of the final design phase of a project.

CODes aND sTaNDaRDs1. The local codes applicable to plumbing systems must

be observed in the design and installation of ordinary plumbing fixtures and potable water and drainage lines for the facility.

2. 10-CFR-58 is the code (by the agencies of the federal government) for good laboratory practice for nonclinical laboratory studies.

3. 21-CFR-211, cGMP, requires compliance with FDA protocols for pharmaceutical applications.

4. NIH publication 86-23, Guide for the Care and Use of Laboratory Animals.

5. American Association for Accrediation of Laboratory Animal Care (AAALAC). Inspection and accreditation by the AAALAC is accepted by the NIH as assurance that the facility is in compliance with Public Health Services (PHS) standards.

aNImal DRINkING-WaTeR sysTemsThe purpose of the animal drinking-water system is to produce, distribute, and maintain an uninterruptible supply of drinking water with a specific and consistent range of purity to all ani-mals in a facility. There are two general types of systems: an automated central-distribution system and individual water bottles.

sysTem TypesThe great majority of animals used by laboratories for medical and product research are mice, rats, guinea pigs, rabbits, cats, dogs, and primates. Smaller animals and primates are kept in stacked cages, often on racks. Medium-sized animals, such as dogs, goats, and pigs, are kept in kennels or pens. Larger floor areas are required for barnyard animals such as cows. Water-ing can be done either by an automatic, reduced-pressure, cen-tral system, which pipes water from the source directly to each cage, kennel or pen; or by separate drinking bottles or watering devices manually placed in individual cages or pens.

Automated, Central Supply-and-Distribution SystemThe purpose of an automated, central, drinking-water supply system is to automatically treat and distribute drinking water. Ancillary devices are used to flush the system and maintain a uniform and acceptable level of purity.

The system consists of a raw or treated water source, a purifi-cation system, medicinal and disinfection injection equipment if necessary, pressure-reducing stations, and a distribution piping network consisting of a low-pressure room-distribution piping system and a rack-manifold pipe terminating in a drink-ing valve for each cage or pen for the animals. Also necessary is an automated flushing system for the room-distribution piping activated by a flush-sequence panel, and a monitoring system to automatically provide monitoring of such items as drinking-water pressure, flow, and possible leakage.

Animals in cages are kept in animal rooms. Cages are usually placed in multi-tiered, portable or permanent cage racks, which contain a number of cages. The cage rack has an integral piping system installed, called a “rack manifold,” that distributes the water to all cages. The rack manifold could be installed by the manufacturer or in the facility by operating personnel. The rack manifold receives its water from the room-distribution piping. The connection between the room-distribution piping and the rack manifold is made by means of a detachable recoil hose generally manufactured from Polypropylene (PP), nylon, or Eth-ylene-Propylene Diene Monomer (EPDM). This hose is flexible, generally 3⁄8 in. (12 mm) in size and coiled to conserve space. It will stretch to a length of about 6 ft 0 in. (2 m). Each end is pro-vided with a quick-disconnect fitting used to attach the hose to both the room-distribution piping and the rack manifold.

To maintain drinking-water quality, a method of flushing the room-distribution piping and the rack manifold shall be pro-vided. Ancillary equipment includes flushing and sanitizing systems to wash the recoil hose and the cage rack-piping inte-rior.

Water BottlesDrinking water bottles are individual units with an integral

drinking tube that are placed by hand on a bracket in each cage.

Animal-care FacilityPiping Systems

Reprinted from Pharmaceutical Facilities Plumbing Systems, Chapter 7: “Animal-care Facility Piping Systems,” by Michael Frankel. © American Society of Plumbing Engineers.

Plumbing Systems & Design NOVEMBER/DECEMBER 2006 PSDMAGAZINE.ORG

CONTINUING EDUCATION


These bottles could be filled either by hand or automatically via a bottle filler.

Automatic bottle fillers should be considered to reduce the time necessary to fill bottles and minimize water spillage. Bottle fillers are available with manifolds to fit any size bottles. They can be supplied with purified water from a central water supply and—with separate, programmable proportioners—could acidify, chlorinate, and medicate the water as required. The bottle filler automates the filling procedure so that the bottles are correctly positioned during filling and stops the flow when the water reaches a predetermined level.

Flushing SystemIn order to maintain drinking-water quality, the drinking-water distribution system should be flushed periodically. This is accomplished by having the same drinking water that is nor-mally distributed to the animals flow through the piping system at an elevated flow rate, pressure, and velocity. The water is sent to drain and not recovered. This is initiated automatically at the drinking-water pressure-reducing station by the addition of separate regulating valves and pressure-regulating arrange-ments.

Different flushing arrangements are possible, depending on the cost, facility protocol, and purity desired. One method flushes only the main runs by the addition of a solenoid valve at the end of the main run and the provision of a return line to drain from this point. Another method is to flush the mains and the room-distribution piping by adding the solenoid valve at the end of each room-distribution branch with the return line to drain from each room. A third method flushes the entire system, including the rack manifold, by adding a solenoid valve on each cage connection to the room-distribution pipe, which flushes the recoil hose and the rack manifold.

It is accepted practice to replace all the drinking water in the room-distribution piping system at regular intervals, a minimum of twice daily. To approximate the amount of water in the pipe, allow 1 gal (4 L) for each 33 ft 0 in. (10 m) of pipe. General prac-tice is to flush the system with water at about 15 psi (90 kPa) at a rate of 15 gpm (60 L/min). If the drinking water is not purified, it is recommended that the piping be flushed at least twice daily for about 2 min. For purified water, flush once daily for about 1 min. Flushing can be done manually by means of a valve in the pressure-reducing station enclosure or automatically by the addition of a bypass and solenoid valve around the low-pres-sure assembly to the pressure-reducing station. The sequence and duration of the automatic flush cycle is controlled from a flush-sequencer panel.

DRINkING-WaTeR TReaTmeNT sysTemsThe purpose of the drinking-water treatment system is to remove impurities from the raw-water supply to achieve the water quality required by the animals in the facility. In addition, disinfectant and medica-tion can be added to the water during treatment if required.

sysTems DesCRIpTIONThere are no generally recognized and accepted standards for animal drinking-water quality. Purity and consistency requirements depend on the incoming water quality, the established protocol of the end user, the importance of either the initial or

the operating cost of the proposed system, the species of ani-mals housed in the facility, and the animal-housing methods. The overall objective is to eliminate as many variables as pos-sible for the entire period of time the studies or experiments are conducted.

The most often-used treatment for drinking water is reverse osmosis. Other possible treatment methods are distillation and deionization. A discussion of these purification methods appears in the chapter “Water Systems.”

Reverse OsmosisWhen a higher-quality water is required and other types of puri-fied water are not available in a facility, reverse osmosis (RO) is normally selected. Since the amount of water is usually small, a package type unit mounted on a skid is provided and connected directly to the water supply. The RO system is flexible and, when used in combination with DI water supply, will provide water that is virtually contamination free.

Disinfection and Medication of Drinking WaterDisinfection chemical mixtures are added to the animal drink-ing-water supply to eliminate and control bacterial contamina-tion in the central and room-distribution piping system. Medi-cation is added to conform with experimental protocols if nec-essary. These mixtures are usually introduced into the piping system by a self-contained, central, proportioning (injector) unit using facility water pressure. Medication is added to the drinking water using the same proportioning equipment that adds disinfectant. All equipment is available in a wide range of sizes and materials. A schematic detail of a typical central pro-portioner is illustrated in Figure 7-1.

Chlorination Chlorination is a recognized biocidal treat-ment that leaves a residual of chlorine in the entire central-dis-tribution system. Hyperchlorinated water is not as corrosive as acidified water and could be used with brass/copper distribution system components. Accepted practice is to provide a pH higher than 4, with a residual range of free chlorine between 5 and 12 ppm. Free chlorine in water dissipates in time with light, heat, and reaction with organic contaminants, making it ineffective when water bottles are used. Chlorine creates toxic compounds in reaction with some water contaminants and medications.

Acidification Acidification has an advantage over chlori-nation in that it is more stable and lasts longer in the system. The disadvantage is that corrosion-resistant materials must be used. The pH range should be between 2.5 and 3 in order to be effec-

Figure 7-1 Typical Central Proportioning Unit

NOVEMBER/DECEMBER 2006 Plumbing Systems & Design


tive. A pH lower than 2.5 will cause the water to become “sour” and the animals will not drink it. At a pH above 3, the mixture is not considered an effective germicide.

DRINkING-WaTeR sysTem COmpONeNTs aND seleCTION

pRessURe-ReDUCING sTaTIONThe pressure-reducing station reduces the normal pressure of the raw-water supply to a level required for the animal-room drinking-water distribution system. As an option, a secondary system can be added to provide a higher pressure in the room-distribution system for flushing.

The pressure and flow rate depend on the type and number of animals to be supplied. Also usually included are a 5-µ water filter, a pressure gauge, and a backflow preventer. Timing devices that automatically control flushing duration are con-trolled by a remote flush-sequencer panel, which controls all flushing sequencing operations. The recommended pressures for animal-room piping distribution to various animals are as follows:

Small animals, such as Rats and mice 3-5 psig (20.4-34 kPa)Primates 3-5 psigDogs and cats 3-5 psigSwine and piglets 6-12 psig (41-81.6 kPa)

The secondary pressure-reducing assembly used to provide automatically room-distribution pipe-flushing water operates at a pressure of 15 psig (102 kPa). This assembly is installed as a bypass around the low-pressure assembly. Manual operation at a lower cost could also be provided. This additional pressure for a short period of time will not cause the animals any difficulty if they decide to drink during the flushing cycle.

One pressure-reducing station can be connected to as many as 35 interconnect stations to small animal-rack manifolds, often referred to as “drops.” This allows 1 station to control more than 1 animal room.

The pressure-reducing station is a preassembled unit com-plete with all the various valves, fittings, and reducing valves required for a specific project. All the components are installed in a cabinet, which requires only mounting and utility connec-tions.

DRINkING ValVesDrinking valves are used by the animals to obtain water from the distribution-system piping. An internal mechanism keeps the valve normally closed; the animal drinking from the valve must open it by some action, such as moving the entire valve or operating a small lever inside the body of the valve with the tongue. Many different kinds of valve are available to supply any type of animal that may be kept in the facility. The valves can be mounted on cages, on the rack manifold, or on the walls of pens and kennels at varying heights with the use of special brackets.

aNImal-RaCk maNIfOlD CONfIGURaTIONsThe configuration of the piping on the animal rack plays an important part in the effectiveness and efficiency of the filling and flushing of the drinking-water system. The two most often-used configurations are the reverse “S” and the “H.”

The reverse “S,” illustrated in Figure 7-2, is the most often-used configuration. It has two basic styles based on the valve location in the flush drain line. One style has a supply control valve at the top and the other has a drain valve at the bottom. Either location is acceptable, with the deciding factor being the ease of operating the valve where the rack is installed. This configuration has the advantage of eliminating dead legs and offers more convenience to facility personnel when they fill the piping after washing. The vent is a manually operated air bleed used when the cage rack is reconnected to the room-distribution pipe. It is opened until water is discharged, thereby eliminating any air pockets in the manifold. This manifold style provides a positive exchange of water during flushing with a minimum usage of time and water.

Figure 7-2 Reverse “S” Configuration Watering Manifold

Figure 7-3 Typical Room Distribution, On-Line, Rack Manifold Flushing System

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CONTINUING EDUCATION: Animal-care Facility Piping Systems


This configuration is used far more than any other manifold style. It is easily converted to automatic flushing by the installation of solenoid devices on the valve. It is recom-mended when micro-isolator cage systems are installed. The complete, on-line, rack-manifold flushing system is illustrated in Figure 7-3. This cage system has the advan-tage of the complete isolation of individual cages, with the accompanying capability for additional flushing and disinfection of the piping system.

One variation of the reverse “S” is the standard “S,” illustrated in Figure 7-4. This configuration has the advantage of com-plete on-line flushing and lower initial cost of the manifold. Disadvantages are the need for extra supports on the cage rack and the need for venting to be done man-ually or by the animals after being placed in service. This configuration is no longer recommended.

The “H” style, illustrated in Figure 7-5, although rigidly installed and with positive venting, is not suitable for on-line flushing. Because of this, it is rarely used except for larger ani-mals, which will consume all the water in the rack piping mani-fold.

The most common piping materials are CPVC and 304L stain-less steel. CPVC conforms to ASTM D 2846, is 0.875 outside diameter (OD) with 0.188 in. minimum wall thickness. Joining process is done with solvent cement socket joints. The drinking valves are installed with a proprietary, drilled and tapped fit-ting. The 304L stainless steel tubing is 0.50 OD with a 0.036 in. minimum wall thickness. Fittings are made with O-ring joints and socket fittings or compression type fittings. The mounting of both pipe materials is accomplished by the use of 304 SS stain-less-steel clamps and fasteners.

sysTem sIzING meThODsThe water consumption of small animals in cages is very low. It is also probable that the animal room will not be used to full capacity. Because of this low consumption flow rate, the flush-ing-water flow rate of the system is the critical factor in sizing the piping. Typically, the animal-room piping distribution net-work is a header uniformly sized at ½ in. (50 mm) throughout the animal room.

The pipe sizes in other areas of the animal facility are determined based on the requirements of maximum flow rate at the necessary pressure to supply the flush-ing velocity. Maximum flow rate depends on the flush sequencing, and the pressure drop depends on overcoming pressure loss through the equipment connected to the branch being sized—such as pressure-reducing stations, solenoid valves, and recoil hoses—and friction loss through the piping network. Allowance must be made to provide a sufficiently high flow rate and water velocity to efficiently provide the flushing action desired.

CleaNING aND DRaINaGe sysTems aND pRaCTICes

GeNeRalKeeping the animal rooms and cages

clean is an extremely important facet of facility practice. The cleaning of the animal room is accomplished either by sponging the walls, floors, and ceiling or by hosing down the room. Cage racks can be cleaned by washing them with a hose or by placing them in a large washing machine. Cages are cleaned in a cage washer. Pens and kennels are hosed down. Floors in pens are cleaned with hoses and the bedding with feces is pushed into trenches with floor drains.

In specialized areas, such as holding or isolation rooms where only small animals are kept, it is common practice to have per-manent cage racks or have the portable racks remain in the animal room. The litter is put into bags and brought to other areas for disposal. The cage racks are manually wiped down and no rack washer is required. A sink is usually provided in the animal room for the convenience of the cleaning personnel. Individual water bottles, if provided, could be washed in the sink. The cages are removed and washed separately in a cage washer. This type of animal room usually does not require a floor drain if the entire room will be sponged down. If hosing is practiced, a floor drain is required.

Rabbits and guinea pigs have a tendency to spray urine and feces. This requires that the racks be hosed down in the room. A wash station with a hose reel and detergent injection capability to hose down the cage racks and the room itself is usually placed in individual rooms. Citric acid is often used as a cleaning agent for rabbits.

hOse sTaTIONsHose stations usually consist of a mixing valve with cold water and steam to make hot water or hot water alone, a length of flex-ible hose, and an adjustable spray nozzle. Hot and cold water are also used. It can be exposed or provided with an enclosure when an easily cleaned surface is required.

CleaNING-aGeNT sysTemsCleaning agents are used to clean and/or disinfect the walls, ceiling, and floor of a room and to add agent to the cage wash water. When used to clean rooms, the equipment used for this purpose is commonly called a “facility detergent system.” When used to add agent to the cage washing water it is often called a “cage-washing detergent system.” These are separate systems and are not capable of providing agent to each other.

Figure 7-4 Standard “S” Configuration Manifold

Figure 7-5 Standard “H” Configuration Manifold



A single-station detergent-dispensing system is used when rooms are cleaned with mops or squeegees. It consists of a wall-mounted unit having a holder for detergent concentrate and an injector unit. A container filled with detergent concentrate is placed in the holder and is used to supply agent to the injector that dispenses a metered amount of agent when a hose bibb is opened to fill the pail or container. These rooms usually have sinks and mop racks inside to be used only for these rooms. A typical schematic detail of a single-station detergent system is illustrated in Figure 7-6.

When used to supply a single or multiple-spray hose for cleaning floors and walls, a central system could be installed to supply several rooms within a facility by means of a detergent pump that dispenses agent. A 55-gal drum of agent should be used to reduce the number of times the

supply has to be changed. A typical central-supply deter-gent-dispensing system is illustrated in Figure 7-7.

The cage-washing detergent system is usually located in the wet area of the cage-washing facility and, with the use of a detergent pump, could be used as a central system to supply cage and bottle washers. A typical schematic detail of a cage-washing system is illustrated in Figure 7-8.

It is common practice to have a central system or a wall-mounted cleaning-agent dispenser unit along with the hose station. Separate, portable units could be used when cross contamination between animal rooms is a consideration. A typical, wall-mounted, cleaning-agent system consists of separate water and cleaning-agent tanks; a water pump; and a special, coaxial hose that sprays a proportioned mix-ture of the water and cleaning agent. Compressed air is often used to provide pressure.

CaGe-flUshING WaTeR sysTemThe removal of animal waste from cages can be done by sev-eral methods. One method removes the waste along with the bedding at the time cages are removed from the animal room to be washed. Another method uses an independent rack-flush system to automatically remove animal waste from cages on racks while the animals and cages remain in the animal room.

The independent rack flush is a separate system that uses chlorinated water automatically distributed to each animal room. The cages and racks are constructed so that

the animal droppings fall through the cage floor onto a sloping pan below each tier of cages. Each tier is cascaded at the end onto the sloping pan below. Eventually, the lowest pan spills into a drain trough in the animal room. The flushing schedule is decided by facility personnel.

The water supply could be a reservoir placed on the rack that is filled with water and automatically discharged onto the pans at preset intervals. These preset intervals are determined based on experience and generally range from once to three times daily. Another method uses a solenoid valve to automatically discharge water onto the pans; the valve is sequenced by a timer set to alternate fill and dump cycles. The timer could be either

Figure 7-6 Single-Station Detergent System

Figure 7-8 Typical Cage-Washing Detergent System

Figure 7-7 Central-Supply Detergent System




centrally located or installed separately in each animal room. Larger cages, such as those for primates, are usually stacked no more than two cages high. Current practice is to have these cages manually cleaned by personnel who hose down the pans directly into floor or wall troughs.

Water is supplied to each cage rack by means of a recoil hose, which has a different quick-disconnect end than that of the drinking water recoil hose to avoid cross connection. Refer to Figure 7-9 for a detail of a typical cage-rack utility connection arrangement.

sOlID-WasTe DIspOsalSolid waste consists of bedding, feces, animal carcasses, and other miscella-neous waste, including straw and sawdust used for larger farm animals. Bedding comprises the largest quantity of this solid waste. It is necessary to determine the quantity of bedding before a decision can be made as to the most cost-effective method to dispose of it.

Bedding can be disposed of by incin-eration, as regular garbage, or into the sewer system. Incinerators are costly, require compliance with many regulatory agencies and multiple permits, and often result in objections from adjoining prop-erty owners. Incineration is the preferred method of disposing of carcasses and large quantities of contaminated waste. Carcasses could also be autoclaved and

disposed of as regular garbage. Regular gar-bage disposal is the most common method of disposal. It involves collecting, moving, and storage of the waste into large containers until regular garbage collection is made. This is very labor intensive.

Discharge into the drainage system must first be accepted by the local authorities and responsible code officials. This requires the bedding to be water soluble, that it shall not float, and provision be made to thoroughly mix the bedding with water. This mixture is called a “slurry.” Experience has shown, if done prop-erly, discharge into an adequately sized drain line—minimum size 6 in. (150 mm)—has caused no problems, since the effluent has the same general characteristics of water.

A self-contained waste-disposal system is available that is capable of disposing of animal bedding and waste. The system consists of a pulping unit to grind the waste into a slurry and sanitize it, a water extractor to remove most of the water from the slurry, and the interconnecting piping system that transports the slurry from the pulper to the extractor and recirculates the water removed from the extractor back to the pulping unit for reuse. The solid waste is removed as garbage. Manufac-turers are available for assistance in the design and equipment selection for this specialized

system. The system has the advantages of reducing water use, reducing operating costs by eliminating the handling of the waste by operating personnel, compacting the waste to about 20% of the space required for standard garbage not compacted, and reducing the possibility of contamination by isolation of the disposal equipment. The disadvantage is its high initial cost.

Figure 7-9 Typical Cage-Rack Utility Connections

Figure 7-10 Typical Waste-Disposal System



This system could consist of single or multiple units of dif-ferent capacities. It requires water intermittently for pulping at the rate of about 10 to 30 gpm (63 to 190 L/min). Hose bibbs should be installed for washdown. The pipe should be sized for a maximum velocity of 8 fps (1.75 m/s), with typical slurry lines ranging between 2 and 4 in. (50 and 200 mm) and return lines generally 2 in. (50 mm) in size. The extractor discharges into a drain that should be 4 or 6 in. (100 or 150 mm) depending on the flow. A typical schematic diagram of a multiple installation is illustrated in Figure 7-10.

ROOm-WasTe DIspOsalThe rooms in which animals are kept must be designed to allow proper drainage practices and in accordance with the antici-pated cleaning procedures of the facility. Floor drains, drainage trenches (or troughs) at room sides, adequate and consistent floor pitch to drains or troughs, and floor surfaces are all impor-tant considerations.

There are several considerations to be taken into account in locating floor drains. Experience has shown that placing drains in the center of a room is not acceptable because it is difficult to hose solids down a drain in this location. Another reason is that the floor must be pitched to the drain and if a cage rack is defective, it should roll to the side of the room. The best loca-tion is in a corner or at the side. Floor drains without troughs can be considered if the floors will only be squeegeed rather than hosed down. They should also be considered in contagious areas where contamination between rooms must be avoided. Gratings must have openings smaller than the wheels of racks or cages.

In rooms where washdown and cage-rack flushing are expected, the provision of a floor trough should be consid-ered. Troughs are often provided at opposite ends of the room to minimize the amount of floor drop due to pitch. Accepted practice uses a minimum floor pitch of 1⁄8 in./ft of floor run. The floor is pitched to the troughs to facilitate cleaning and also to provide an easy method to dispose of waste generated from the rack-flush system. It is common practice to provide an auto-matic or manual trough-flushing system with nozzles or jets to wash down the trough sides and eliminate as much of the con-tamination remaining in the trough as possible. Wall troughs, similarly to roof gutters, are located at a higher elevation. This type of trough arrangement is sometimes provided in addition to or in lieu of floor troughs if the arrangement of elevated cages and racks make it an effective drainage method. Experience has shown that prefabricated drain troughs in floors are preferred over those built on the wall as part of the architectural construc-tion.

The floor troughs are drained by means of a floor drain placed in a low point at one end. The troughs are usually pitched at ¼ in./ft of run to the drain. The drain should be constructed of acid-resistant materials and have a grate that can be easily removed. For small animal rooms where bedding is not disposed of in the room, a 4-in. (100-mm) drain is considered adequate. In most other locations, it is recommended that a 6-in. (150-mm) drain be provided. A flushing-rim type drain should be considered to flush all types of waste into the drainage system.

Floor drains should have the capability of being sealed by the replacement of the grates with solid covers during periods when the room may not be in service.

eqUIpmeNT WashINGMost facilities contain washing and sanitizing machines to wash cages, cage racks, and bottles, if used. There are two commonly used types of cage washer: the batch type and conveyer (tunnel) type. Batch washers require manual loading and unloading and are used where a small number of cages and racks are washed. The conveyer type is similar to a commercial dishwasher, where the cages and racks are loaded on a conveyer and automatically moved through the machine for the washing and sanitizing cycles.

eqUIpmeNT saNITIzINGMaintaining drinking-water quality requires that the recoil hoses and rack manifolds be not merely washed but internally sanitized. This is most often done at the same time the cages are washed. Separate rack-manifold and recoil-hose flush stations are available for this purpose and are usually installed in the cage-wash area. Washing can be done manually or automati-cally. The hoses are flushed for 1 to 2 min with 4 gpm (16 L/min) of water. Chlorine is injected into the water by a chlorine-injec-tion station (proportioner) set to deliver 10 to 20 ppm into the flush water. Ten scfm of oil-free compressed air at 60 psig is blown through the hoses to dry them. If chlorine is used as a disinfectant, a contact time of 30 min is recommended before evacuation and drying.

Periodic sanitizing of the room-distribution piping system is required for maintaining good water quality. Sanitizing is done prior to system flushing. To accomplish this, a portable sanitizer is used to manually inject a sanitizing solution directly into the piping system. In order to do this, an injection port is required at the inlet to the pressure-reducing station. The portable sani-tizer usually consists of a 20-gal (90-L) polyethylene tank with a submersible pump inside and a flexible hose used to connect the tank to the injection port. The disinfecting solution is a mix-ture of chlorine and water with 20 ppm of chlorine. The mixture should maintain a contact time in the piping of 30 to 45 min.

DRaINaGe-sysTem sIzINGAs mentioned previously, for individual animal rooms where bedding is not disposed of in the drainage system, a 4-in. drain is acceptable. In general, a 6-in. drain is considered good practice. The size of the drainage system piping should be a minimum of 6 in., with a ¼-in. pitch when possible and the piping sized to flow ½ to 2⁄3 full in order to accommodate unexpected inflow.

mONITORING sysTemsThe monitoring of various animal-utility systems is critical to keep within a range of values consistent with the protocol of the experiments being conducted at the facility. This is accom-plished by a central monitoring system that includes many mea-surements from HVAC and electrical systems. For the animal drinking-water system, parameters such as water pressure, flow rates, leakage, pH, and temperature in various areas of the facil-ity are helpful for maintenance, monitoring, and alarms.

sysTems DesIGN CONsIDeRaTIONsThe amount of exposed piping inside any animal room should be minimized. The exception is the animal drinking-water system, which is usually exposed on the walls of the room. This piping should be installed using standoffs to permit proper cleaning of the wall and around the pipe.

The piping material used for all systems should be selected with consideration given to the facility cleaning methods and




type of disinfectant. Where sterilization is required and cleaning very frequent, stainless-steel pipe should be considered.

If insulation is used on piping, it should be protected with a stainless steel jacket to permit adequate cleaning.

Pipe penetrations should be sealed with a high-grade, imper-vious, and fire-resistant sealant. Escutcheons should not be used because they allow the accumulation of dirt and bacteria behind them.




PSD

136


CE Questions—“Animal-care Facility Piping Systems” (PSD 136)

About This Issue’s ArticleThe November/December 2006 Continuing Education

article is “Animal-care Facility Piping Systems,” Chapter 7 of Pharmaceutical Facilities Plumbing Systems by Michael Frankel. This chapter discusses the various piping systems uniquely associated with the physical care, health, and well-being of laboratory animals. Included are utility systems for animal watering, water treatment, room and floor cleaning, equipment washing, cage flushing and drainage, and other specialized piping required for laboratory and experimental work within the facility.

You may locate this article at www.psdmagazine.org. Read the article, complete the following exam, and submit your answer sheet to the ASPE office to potentially receive 0.1 CEU.

1. What comprises the largest solid waste item from animal cages? a. bedding, b. feces, c. carcasses, d. miscellaneous waste

. This chapter discusses various piping systems uniquely associated with the physical care, health, and well-being of ___________.a. laboratory workers, b. laboratory animals,

c. animal watering, d. cage cleaning

. A single-station detergent-dispensing system is used when rooms are ___________.a. hosed downb. cleaned with mops or squeegeesc. cleaned with steamd. none of the above

. To maintain drinking water quality, ___________.a. a water purification system must be designedb. the water system must be allowed to run continuouslyc. there must be chlorine injectiond. the drinking water distribution system must be flushed

periodically

. Floor drains should not be placed ___________ where animals are kept.a. under cages in roomsb. in the center of the roomc. at the back edge of cages in roomsd. none of the above

. A pulping unit is used to ___________.a. separate water from solid wasteb. determine the pH of the wastec. determine the temperature of the wasted. grind the waste into a slurry

. 10-CFR- ___________.a. is the federal code that must be followed when keeping

animals for researchb. requires compliance with FDA protocols for

pharmaceutical applications

c. is the guide for the care and use of laboratory animalsd. is the code for good laboratory practice for non-clinical

laboratory studies

. Select the true statement below.a. There are no generally recognized and accepted

standards for animal drinking water.b. Drinking valves are not used by animals to obtain water

from the distribution system.c. Water pressure, minimum and maximum, for the

various animals to be served is mandated in the plumbing code.

d. Reverse osmosis (RO) systems are inappropriate for animal drinking water systems.

. The recommended water pressure for dogs and cats is ___________.a. 6–12 psig, b. 20.4–34 kPa,

c. more than for rats and mice, d. none of the above

10. What flow rate and pressure of oil-free air is used to dry the interior of hoses?a. 5 scfm at 30 psigb. 10 scfm at 30 psigc. 5 scfm at 60 psigd. 10 scfm at 60 psig

11. What type of piping material should be used on systems that require frequent sterilization?a. cast ironb. copperc. galvanizedd. stainless steel

1. The water consumption of small animals in cages is ___________.a. based on a flushing system to maintain fresh water in

the piping at all timesb. established by experiencec. very lowd. none of the above

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NOVEMBER/DECEMBER 2006 Plumbing Systems & Design 11


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143

Recirculating DomesticHot WaterSystemsContinuing education from Plumbing Systems & Design

Haig demergian, Pe, CPd

DECEMBER 2007

PSDMAGAZINE.ORG


INTRODUCTIONIt has been determined through field studies that the correct sizing and operation of water heaters depend on the appropriateness of the hot water maintenance system. If the hot water maintenance system is inadequate, the water heater sizing criteria are wrong and the temperature of the hot water distributed to the users of the plumb-ing fixtures is below acceptable standards. Additionally, a poorly designed hot water maintenance system wastes large amounts of energy and potable water and creates time delays for those using the plumbing fixtures. This chapter addresses the criteria for estab-lishing an acceptable time delay in delivering hot water to fixtures and the limitations of the length between a hot water recirculation system and plumbing fixtures. It also discusses the temperature drop across a hot water supply system, types of hot water recircula-tion system, and pump selection criteria, and gives extensive infor-mation on the insulation of hot water supply and return piping.

BaCkgROUNDIn the past, the plumbing engineering community considered the prompt delivery of hot water to fixtures either a requirement for a project or a matter of no concern. The plumbing engineer’s decision was based primarily on the type of facility under consideration and the developed length from the water heater to the farthest fixture. Previous reference material and professional common practices have indicated that, when the distance from the water heater to the farthest fixture exceeds 100 ft (30.48 m) water should be circulated. However, this recommendation is subjective, and, unfortunately, some engineers and contractors use the 100-ft (30.48-m) criterion as the maximum length for all uncirculated, uninsulated, dead-end hot water branches to fixtures in order to cut the cost of hot water distribution piping. These long, uninsulated, dead-end branches to fixtures create considerable problems, such as a lack of hot water at fixtures, inadequately sized water heater assemblies, and thermal temperature escalation in showers.

The 100-ft (30.48-m) length criterion was developed in 1973 after the Middle East oil embargo, when energy costs were the paramount concern and water conservation was given little consideration. Since the circulation of hot water causes a loss of energy due to radiation and convection in the circulated system and such energy losses have to be continually replaced by water heaters, the engineering community compromised between energy loss and construction costs and developed the 100-ft (30.48-m) maximum length criterion.

LeNgTh aND TIme CRITeRIaRecently, due to concern about not only energy conservation but also the extreme water shortages in parts of the country, the 100-ft (30.48-m) length criteria has changed. Water wastage caused by the long delay in obtaining hot water at fixtures has become as critical an issue as the energy losses caused by hot water temperature maintenance systems. To reduce the wast-ing of cooled hot water significantly, the engineering com-munity has reevaluated the permissible distances for uncir-

culated, dead-end branches to periodically used plumbing fixtures. The new allowable distances for uncirculated, dead-end branches represent a trade-off between the energy utilized by the hot water maintenance system and the cost of the insulation, on the one hand, and the cost of energy to heat the excess cold water makeup, the cost of wasted potable water, and extra sewer surcharges, on the other hand. Furthermore, engineers should be aware that various codes now limit the length between the hot water maintenance system and plumbing fixtures. They also should be aware of the potential for liability if an owner questions the adequacy of their hot water system design.

What are reasonable delays in obtaining hot water at a fixture? For anything beside very infrequently used fixtures (such as those in industrial facilities or certain fixtures in office buildings), a delay of 0 to 10 sec is normally considered acceptable for most residential occupancies and public fixtures in office buildings. A delay of 11 to 30 sec is marginal but possibly acceptable, and a time delay longer than 31 sec is normally considered unacceptable and a significant waste of water and energy. Therefore, when designing hot water systems, it is prudent for the designer to provide some means of getting hot water to the fixtures within these acceptable time limits. Normally this means that there should be a maximum distance of approximately 25 ft (7.6 m) between the hot water maintenance system and each of the plumbing fixtures requiring hot water, the distance depending on the water flow rate of the plumbing fixture at the end of the line and the size of the line. (See Tables 1, 2, and 3.) The plumbing designer may want to stay under this length limita-tion because the actual installation in the field may differ slightly from the engineer’s design, and additional delays may be caused

Recirculating Domestic Hot Water Systems

Reprinted from Domestic Water Heating Design Manual, Second Edition, Chapter 14: “Recirculating Domestic Hot Water Systems.” © American Society of Plumbing Engineers , 2003.

2 Plumbing Systems & Design DECEMBER 2007 PSDMAGAZINE.ORG

CONTINUINg eDUCaTION

Table 1 Water Contents and Weight of Tube or Piping per Linear FootNominal Diameter

Copper Pipe Type L

Copper Pipe Type M

Steel Pipe Schedule 40

CPVC Pipe Schedule 40

(in.)aWater

(gal/ft)Wgt.

(lb/ft)Water

(gal/ft)Wgt.

(lb/ft)Water

(gal/ft)Wgt.

(lb/ft)Water

(gal/ft)Wgt.

(lb/ft)½ 0.012 0.285 0.013 0.204 0.016 0.860 0.016 0.210¾ 0.025 0.445 0.027 0.328 0.028 1.140 0.028 0.290

1 0.043 0.655 0.045 0.465 0.045 1.680 0.045 0.4201¼ 0.065 0.884 0.068 0.682 0.077 2.280 0.078 0.5901½ 0.093 1.14 0.100 0.940 0.106 2.720 0.106 0.710

a Pipe sizes are indicated for mild steel pipe sizing.

Table 1(M) Water Contents and Weight of Tube or Piping per MeterNominal Diameter

Copper Pipe Type L

Copper Pipe Type M

Steel Pipe Schedule 40

CPVC Pipe Schedule 40

(mm)aWater

(L)Wgt. (kg)

Water (L)

Wgt. (kg)

Water (L)

Wgt. (kg)

Water (L)

Wgt. (kg)

DN15 0.045 0.129 0.049 0.204 0.061 0.390 0.061 0.099DN20 0.095 0.202 0.102 0.328 0.106 0.517 0.106 0.132DN25 0.163 0.297 0.170 0.465 0.170 0.762 0.170 0.191DN32 0.246 0.401 0.257 0.682 0.291 1.034 0.295 0.268DN40 0.352 0.517 0.379 0.940 0.401 1.233 0.401 0.322

a Pipe sizes are indicated for mild steel pipe sizing.


by either the routing of the pipe or other problems. Furthermore, with the low fixture discharge rates now mandated by national and local laws, it takes considerably longer to obtain hot water from non-temperature maintained hot water lines than it did in the past, when fixtures had greater flow rates. For example, a public lavatory with a 0.50 or 0.25 gpm (0.03 or 0.02 L/sec) maximum discharge rate would take an excessive amount of time to obtain hot water from 100 ft (30.48 m) of uncirculated, uninsulated hot water piping. (See Table 3.) This table gives conservative approximations of the amount of time it takes to obtain hot water at a fixture. The times are based on the size of the line, the fixture flow rate, and the times required to replace the cooled off hot water, to heat the pipe, and to offset the convection energy lost by the insulated hot water line.

ResULTs Of DeLays IN DeLIveRINg hOT WaTeR TO fIxTUResAs mentioned previously, when there is a long delay in obtaining hot water at the fixture, there is significant wastage of potable water as the cooled hot water supply is simply discharged down the drain unused. Furthermore, plumbing engineers concerned about total system costs should realize that the cost of this wasted, previously heated water must include: the original cost for obtaining potable water, the cost of previously heating the water, the final cost of the waste treatment of this excess potable water, which results in larger sewer surcharges (source of supply to end disposal point), and the cost of heating the new cold water to bring it up to the required tem-perature. Furthermore, if there is a long delay in obtaining hot water at the fixtures, the faucets are turned on for long periods of time to bring the hot water supply at the fixture up to the desired tempera-

ture. This can cause the water heating system to run out of hot water and make the heater sizing inadequate, because the heater is unable to heat all the extra cold water brought into the system through the wastage of the water discharged down the drain. In addition, this extra cold water entering the hot water system reduces the hot water supply tempera-ture. This exacerbates the problem of insufficient hot water because to get a proper blended temperature more lower temperature hot water will be used to achieve the final mixed water temperature. (See Chapter 1, Table 1.1.) Additionally, this accelerates the downward spiral of the temperature of the hot water system.

Another problem resulting from long delays in getting hot water to the fixtures is that the fixtures operate for longer than expected periods of time. Therefore, the actual hot water demand is greater than the demand normally designed for.

Therefore, when sizing the water heater and the hot water piping distribution system, the designer should be aware that the lack of a proper hot water maintenance system can seriously impact the required heater size.

meThODs Of DeLIveRINg ReasONaBLy PROmPT hOT WaTeR sUPPLy Hot water maintenance systems are as varied as the imagina-tions of the plumbing engineers who create them. They can be grouped into three basic categories, though any actual installation may be a combination of more than one of these types of system. The three basic categories are1. Circulation systems.2. Self-regulating heat trace systems.3. Point-of-use water heaters (include booster water heat-

ers).

CirCulation SyStemS for CommerCial, induStrial, and large reSidential ProjeCtSA circulation system is a system of hot water supply pipes and hot water return pipes with appropriate shutoff valves,

balancing valves, circulating pumps, and a method of controlling the circulating pump. The diagrams for six basic circulating systems are shown in Figures 1 through 6.

Self-regulating Heat traCeOver approximately the last 20 years, self-regulating heat trace has come into its own because of the problems of balancing circulated hot water systems and energy loss in the return piping. For further discussion of this topic, see Chapter 15.

DECEMBER 2007 Plumbing Systems & Design 3

Table 3 Approximate Time Required to Get Hot Water to a FixtureDelivery Time (sec)

Fixture Flow Rate (gpm) 0.5 1.5 2.5 4.0

Piping Length (ft) 10 25 10 25 10 25 10 25

Copper ½ in. 25 63a 8 21 5 13 3 8 Pipe ¾ in. 48a 119a 16 40a 10 24 6 15Steel Pipe ½ in. 63a 157a 21 52a 13 31a 8 20 Sched. 40 ¾ in. 91a 228a 30 76a 18 46a 11 28CPVC Pipe ½ in. 64a 159a 21 53a 13 32a 8 20 Sched. 40 ¾ in. 95a 238a 32 79a 19 48a 12 30

Note: Table based on various fixture flow rates, piping materials, and dead-end branch lengths. Calculations are based on the amount of heat required to heat the piping, the water in the piping, and the heat loss from the piping. Based on water temperature of 140°F and an air temperture of 70°F.a Delays longer than 30 sec are not acceptable.

Table 3(M) Approximate Time Required to Get Hot Water to a FixtureDelivery Time (sec)

Fixture Flow Rate (L/sec) 0.03 0.10 0.16 0.25

Piping Length (m) 3.1 7.6 3.1 7.6 3.1 7.6 3.1 7.6

Copper DN15 25 63a 8 21 5 13 3 8 Pipe DN22 48a 119a 16 40a 10 24 6 15Steel Pipe DN15 63a 157a 21 52a 13 31a 8 20 Sched. 40 DN20 91a 228a 30 76a 18 46a 11 28CPVC Pipe DN15 64a 159a 21 53a 13 32a 8 20 Sched. 40 DN20 95a 238a 32 79a 19 48a 12 30

Note: Table based on various fixture flow rates, piping materials, and dead-end branch lengths. Calculations are based on the amount of heat required to heat the piping, the water in the piping, and the heat loss from the piping. Based on water temperature of 60°C and an air temperture of 21.1°C.a Delays longer than 30 sec are not acceptable.

Table 2 Approximate Fixture and Appliance Water Flow Rates

FittingsMaximum Flow Ratesa

GPM L/SecLavatory faucet 2.0 1.3 Public non-metering 0.5 0.03 Public metering 0.25 gal/cycle 0.946 L/cycleSink faucet 2.5 0.16Shower head 2.5 0.16Bathtub faucets Single-handle 2.4 minimum 0.15 minimum Two-handle 4.0 minimum 0.25 minimum Service sink faucet 4.0 minimum 0.25 minimumLaundry tray faucet 4.0 minimum 0.25 minimumResidential dishwasher 1.87 aver 0.12 averResidential washing machine 7.5 aver 0.47 aver

a Unless otherwise noted.


Point-of-uSe HeaterSThis concept is applicable when there is a single fixture or group of fixtures that is located far from the temperature maintenance system. In such a situation, a small, instantaneous, point-of-use water heater—an electric water heater, a gas water heater, or a small under-fixture stor-age type water heater of the magnitude of 6 gal (22.71 L)—can be provided. (See Figure 7.) The point-of-use heater will be very cost-effective because it will save the cost of running hot water piping to a fixture that is a long distance away from the temperature maintenance system. The plumbing engineer must remember, however, that when a water heater is installed there are various code and installation requirements that must be complied with, such as those pertain-ing to T & P relief valve discharge.

Instantaneous electric heaters used in point-of-use applications can require a considerable amount of power, and may require 240 or 480 V service.

POTeNTIaL PROBLems IN CIRCULaTeD hOT WaTeR maINTeNaNCe sysTemsThe following are some of the potential prob-lems with circulated hot water maintenance systems that must be addressed by the plumb-ing designer.

Water VeloCitieS in Hot Water PiPing SyStemSFor copper piping systems, it is very important that the circulated hot water supply piping and especially the hot water return piping be sized so that the water is moving at a controlled veloc-ity. High velocities in these systems can cause pinhole leaks in the copper piping in as short a period as six months or less.

BalanCing SyStemSIt is extremely important that a circulated hot water system be balanced for its specified flows, including all the various individual loops within the circulated system. Balancing is required even though an insulated circulated line usu-ally requires very little flow to maintain satis-factory system temperatures. If the individual hot water circulated loops are not properly bal-anced, the circulated water will tend to short-circuit through the closest loops, creating high velocities in that piping system. Furthermore, the short-circuiting of the circulated hot water will result in complaints about the long delays in getting hot water at the remotest loops. If the hot water piping is copper, high velocities can create velocity erosion which will destroy the piping system.

Because of the problems inherent in manu-ally balancing hot water circulation systems, many professionals incorporate factory preset flow control devices in their hot water systems. While the initial cost of such a device is higher than the cost of a manual balancing valve, a


CONTINUINg eDUCaTION: Recirculating Domestic hot Water systems

* See text for requirements for strainers.

Fixture 1 Upfeed Hot Water System with Heater at Bottom of System.

Figure 2 Downfeed Hot Water System with Heater at Top of System.


Figure 3 Upfeed Hot Water System with Heater at Bottom of System.



preset device may be less expensive when the field labor cost for balancing the entire hot water system is included. When using a preset flow control device, however, the plumbing designer has to be far more accurate in select-ing the control device’s capacity as there is no possibility of field adjustment. Therefore, if more or less hot water return flow is needed during the field installation, a new flow control device must be installed and the old one must be removed and discarded.

iSolating PortionS of Hot Water SyStemSIt is extremely important in circulated systems that shutoff valves be provided to isolate an entire circulated loop. This is done so that if individual fixtures need modification, their piping loop can be isolated from the system so the entire hot water system does not have to be shut off and drained. The location of these shutoff valves should be given considerable thought. The shutoff valves should be acces-sible at all times, so they should not be located in such places as the ceilings of locked offices or condominiums.

maintaining tHe BalanCe of Hot Water SyStemSTo ensure that a balanced hot water system remains balanced after the shutoff valves have been utilized, the hot water return system must be provided with a separate balancing valve in addition to the shutoff valve or, if the balanc-ing valve is also used as the shutoff valve, the balancing valve must have a memory stop. (See the discussion of “balancing valves with memory stops” below.) With a memory stop on the valve, plumbers can return a system to its balanced position after working on it rather than have the whole piping system remain unbalanced, which would result in serious problems.

ProViding CHeCk ValVeS at tHe endS of Hot Water looPSThe designer should provide a check valve on each hot water return line where it joins other hot water return lines. This is done to ensure that a plumbing fixture does not draw hot return water instead of hot supply water, which could unbalance the hot water system and cause delays in obtaining hot water at some fixtures.

a delay in oBtaining Hot Water at dead-end lineSKeep the delay in obtaining hot water at fix-tures to within the time (and branch length) parameters given previously to avoid unhappy users of the hot water system and to prevent lawsuits.

fLOW BaLaNCINg DevICesThe following are the more common types of balancing device.


Figure 4 Downfeed Hot Water System with Heater at Top of System.


Note: This piping system increases the developed length of the HW system over the upfeed systems shown in Figures 1 and 3.* See text for requirements for strainers.

Figure 5 Combination Upfeed and Downfeed Hot Water System with Heater at Bottom of System.

Note: This piping system increases the developed length of the HW system over the downfeed systems shown in Figures 2 and 4.* See text for requirements for strainers.

Figure 6 Combination Downfeed and Upfeed Hot Water System with Heater at Top of System.


fixed orifiCeS and VenturiSThese can be obtained for specific flow rates and simply inserted into the hot water return piping system. (See Figure 8.) However, extreme care should be taken to locate these devices so they can be removed and cleaned out, as they may become clogged with the debris in the water. It is recommended, therefore, that a strainer with a blowdown valve be placed ahead of each of these devices. Additionally, a strainer with a fine mesh screen can be installed on the main water line coming into the building to help prevent debris buildup in the individual strainers. Also, a shutoff valve should be installed before and after these devices so that an entire loop does not have to be drained in order to service a strainer or balancing device.

faCtory PreSet automatiC floW Control ValVeSThe same admonition about strainers and valves given for “fixed orifices and venturis” above applies to the installation and location of these devices. (See Figure 9.)

floW regulating ValVeSThese valves can be used to determine the flow rate by reading the pressure drop across the valve. They are available from various manufacturers. (See Figure 10.)

BalanCing ValVeS WitH memory StoPSThese valves can be adjusted to the proper setting by installing insertable pressure measuring devices (Pete’s Plugs, etc.) in the piping system, which indicate the flow rate in the pipe line. (See Figure 11.)

sIzINg hOT WaTeR ReTURN PIPINg sysTems aND ReCIRCULaTINg PUmPsThe method for selecting the proper size of the hot water return piping system and the recirculating pump is fairly easy, but it does require engineering judgment. First, the plumbing engineer has to design the hot water supply and hot water return piping sys-tems, keeping in mind the parameters for total developed length,1 prompt delivery of hot water to fixtures, and velocities in pipe lines. The plumbing engineer has to make assumptions about the sizes of the hot water return piping.

After the hot water supply and hot water return systems are designed, the designer should make a piping diagram of the hot water supply system and the assumed return system showing piping sizing and approximate lengths. From this piping diagram the hourly heat loss occurring in the circulated portion of the hot water supply and return systems can be determined. (See Table 4 for minimum required insulation thickness and Table 5 for approx-imate piping heat loss.)

Next determine the heat loss in the hot water storage tank if one is provided. (See Table 6 for approximate tank heat loss.) Calculate the total hot water system energy loss (tank heat loss plus piping heat loss) in British thermal units per hour (watts). This total hot water system energy loss is represented by q in Equation 1 below. Note: Heat losses from storage type water heater tanks are not nor-mally included in the hot water piping system heat loss because the water heater capacity takes care of this loss, whereas pumped hot water has to replace the piping convection losses in the piping system. (1) q = 60rwc∆T [q = 3600rwc∆T]

where 60 = min/h 3600 = sec/h q = piping heat loss, Btu/h (kJ/h) r = flow rate, gpm (L/sec) w = weight of heated water, lb/gal (kg/L) c = specific heat of water, Btu/lb/°F (kJ/kg/K) ∆T = change in heated water temperature (tem-

perature of leaving water minus temperature of incoming water, represented in this manual as Th – Tc, °F [K])

Therefore q = c (gpm × 8.33 lb/gal)(60 min/h)(°F temperature

drop) = 1(gpm) × 500 × °F temperature drop [q = c (L/sec • 1kg/L)(3600 sec/h)(K temperature drop) = 1(L/sec) • 15 077 kJ/L/sec/K • K temperature drop]

(2) gpm ≈ system heat loss (Btu/h)500 × °F temperature drop

[L/sec ≈ system heat loss (kJ/h) ]15 077 • K temperature dropIn sizing hot water circulating systems, the designer should note

that the greater the temperature drop across the system, the less water is required to be pumped through the system and, therefore, the greater the savings on pumping costs. However, if the domestic hot water supply starts out at 140°F (60°C) with, say, a 20°F (6.7°C) temperature drop across the supply system, the fixtures near the end of the circulating hot water supply loop could be provided with a hot water supply of only 120°F (49°C). In addition, if the hot water supply delivery temperature is 120°F (49°C) instead of 140°F (60°C), the plumbing fixtures will use greater volumes of hot water to get the desired blended water temperature (see Chapter 1, Table 1.1). Therefore, the recommended hot water system temperature drop should be of the magnitude of 5°F (3°C). This means that if the hot water supply starts out from the water heater at a tempera-ture between 135 and 140°F (58 and 60°C), the lowest hot water supply temperature provided by the hot water supply system could



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Figure 7 Instantaneous Point-of-Use Water Heater Piping Diagram.Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com

be between 130 and 135°F (54 and 58°C). With multiple tempera-ture distribution systems, it is recommended that the recirculation system for each temperature distribution system be extended back to the water heating system separately and have its own pump.

Using Equation 2, we determine that, if there is a 5°F (3°C) tem-perature drop across the hot water system, the number to divide into the hot water circulating system heat loss (q) to obtain the minimum required hot water return circulation rate in gpm (L/sec) is 2500 (500 × 5°F), (45 213 [15 071 • 3°C]).

For a 10°F (6°C) temperature drop that number is 5000 (from Equation 2, 500 × 10°F = 5000) (90 426 [from Equation 2, 15 071 • 6°C = 90 426]). However, this 10°F (6°C) temperature drop may produce hot water supply temperatures that are lower than desired.

After Equation 2 is used to establish the required hot water return flow rate, in gpm (L/sec), the plumbing designer can size the hot water return piping system based on piping flow rate velocities and the available pump heads. It is quite common that a plumb-ing designer will make wrong initial assumptions about the sizes

of the hot water return lines to establish the initial heat loss figure (q). If that is the case, the plumbing engineer will have to correct the hot water return pipe sizes, redo the calculations using the new data based on the correct pipe sizing, and verify that all the rest of the calculations are now correct.

examPLe 1 — CaLCULaTION TO DeTeRmINe ReQUIReD CIRCULaTION RaTe1. Assume that the hot water supply piping system has 800 ft (244 m) of average size 1 ¼ in. (DN32) pipe. From Table 5, determine the heat loss per linear foot (meter). To find the total heat loss, multiply length times heat loss per foot (meter):

800 ft × 13 Btu/h/ft = 10,400 Btu/h supply piping losses(244 m • 12.5 W = 3050 W supply piping losses)

2. Assume that the hot water return piping system for the system in no. 1 above has 100 ft (30.5 m) of average ½ in. (DN15) piping and 100 ft (30.5 m) of average ¾ in. (DN20) pipe. From Table 5 determine the heat loss per linear foot (meter):

100 ft × 8 Btu/h/ft = 800 Btu/h piping loss(30.5 m • 7.7 W/m = 235 W piping loss)

100 ft × 10 Btu/h/ft = 1000 Btu/h piping loss1800 Btu/h piping loss

(30.5 m • 9.6 W/m = 293 W piping loss )528 W piping loss

3. Determine the hot water storage tank heat loss. Assume the system in no. 1 above has a 200-gal (757-L) hot water storage


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Figure 8 Fixed Orifices and Venturi Flow Meters.

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Figure 9 Preset Self-Limiting Flow Control Cartridge.Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com

tank. From Table 6 determine the heat loss of the storage tank @ 759 Btu/h (222 W).

4. Determine the hot water system’s total heat losses by totaling the various losses:

A. Hot water supply piping losses 10,400 Btu/h B. Hot water return piping losses 1,800 Btu/h C. Hot water storage tank losses 759 Btu/h Total system heat losses 12,959 Btu/h Total system piping heat losses (A + B) = 12,200 Btu/h [A. Hot water supply piping losses 3050 W B. Hot water return piping losses 527 W C. Hot water storage tank losses 222 W Total system heat losses 3799 W Total system piping heat losses (A + B) = 3577 W]

From Equation 2, using a system piping loss of 12,200 Btu/h (3577 W) and a 5°F (3°C) temperature drop,

12,200 Btu/h = 4.88 gpm (say 5 gpm) required hot water return circulation rate

5°F temperature difference × 500

3577 W = 0.29 (say 0.3) L/sec required hot water return circulation

3°C temp. difference • 4188.32 kJ/m3

reCalCulation of Hot Water SyStem loSSeS1. Assume that the hot water supply piping system has 800 ft

(244 m) of average size 1¼ in. (DN32) pipe. From Table 5 determine the heat loss per linear foot (meter):

800 ft × 13 Btu/h/ft = 10,400 Btu/h piping loss(244 m • 12.5 W/m = 3050 W piping loss)

2. Assume that the hot water return piping system for the system in no. 1 above has 100 ft (30.5 m) of average ½ in. (DN15) pipe, 25 ft (7.6 m) of average ¾ in. (DN22) pipe, and

75 ft (22.9 m) of average 1 in. (DN28) pipe. From Table 5, determine the heat loss per linear foot (meter):

100 ft × 8 Btu/h/ft = 800 Btu/h piping loss 25 ft × 10 Btu/h/ft = 250 Btu/h piping loss 75 ft × 10 Btu/h/ft = 750 Btu/h piping loss 1800 Btu/h piping loss

[30.5m•7.7W/m= 235Wpipingloss



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Figure 10 Adjustable Orifice Flow Control Valve.

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Figure 11 Adjustable Balancing Valve with Memory Stop.


7.6m•9.6W/m= 73Wpipingloss 22.9m•9.6W/m= 220 W piping loss 528 W piping loss]

3. Determine the hot water storage tank heat loss. Assume the system in no. 1 above has a 200-gal (757-L) hot water storage tank. From Table 6 determine the heat loss of the storage tank @ 759 Btu/h (222 W).

4. Determine the system’s total heat losses: A. Hot water supply losses 10,400 Btu/h B. Hot water return losses 1,800 Btu/h C. Hot water storage tank losses 759 Btu/h Total system heat losses 12,959 Btu/h Total system piping heat losses (A + B) = 12,200 Btu/h

[A. Hot water supply losses 3050 W B. Hot water return losses 528 W C. Hot water storage tank losses 222 W Total system heat losses 3800 W Total system piping heat losses (A + B) = 3578 W]

Note: The recalculation determined that the hot water system heat losses remained unchanged and that 4.88 (say 5) gpm (0.29 [say 0.3] L/sec) is the flow rate that is required to maintain the 5°F (3°C) temperature drop across the hot water supply system.

It should be stated that engineers use numerous rules of thumb to size hot water return systems. These rules of thumb are all based on assumptions, however, and are not recommended. It is recom-mended that the engineer perform the calculations for each project to establish the required flow rates because, with all the various capacities of the pumps available today, exact sizing is possible, and any extra circulated flow caused by the plumbing engineer using a rule of thumb equates to higher energy costs, to the detriment of the client.

esTaBLIshINg The heaD CaPaCITy Of The hOT WaTeR CIRCULaTINg PUmP

Table 4 Minimum Pipe Insulation ThicknessRequired Insulation Thickness for Piping (in.)

Runouts 2 in. or Lessa 1 in. or Less 1¼–2 in. 2½–4 in. 5 & 6 in.

8 in. or Larger

½ 1 1 1½ 1½ 1½Note: Data based on fiberglass insulation with all-service jacket. Data will change depending on actual type of insulation used. Data apply to recirculating sections of hot water systems and the first 3 ft from the storage tank of uncirculated systems.a Uncirculated pipe branches to individual fixtures (not exceeding 12 ft in length). For lengths longer than 12 ft, use required insulation thickness shown in table.

Table 4(M) Minimum Pipe Insulation ThicknessRequired Insulation Thickness for Piping (mm)

Runouts DN32 or

LessaDN25 or

LessDN32–DN50

DN65–DN100

DN125 & DN150

DN200 or Larger

13 25 25 40 40 40Note: Data based on fiberglass insulation with all-service jacket. Data will change depending on actual type

of insulation used. Data apply to recirculating sections of hot water systems and the first 0.9 m from the storage tank of uncirculated systems.

a Uncirculated pipe branches to individual fixtures (not exceeding 3.7 m in length). For lengths longer than 305 mm, use required insulation thickness shown in table.

Table 5 Approximate Insulated Piping Heat Loss and Surface Temperature

Nominal Pipe Size (in.)

Insulation Thickness (in.)

Heat Loss (Btu/h/ linear ft)

Surface Temperature

(°F)½ 1 8 68¾ 1 10 69

1 1 10 691¼ 1 13 701½ 1 13 692 or less ½a 24 or less 742 1 16 702½ 1½ 12 673 1½ 16 684 1½ 19 696 1½ 27 698 1½ 32 69

10 1½ 38 69Note: Figures based on average ambient temperature of 65°F and annual average wind

speed of 7.5 mph.a Uncirculating hot water runout branches only.

Table 5(M) Approximate Insulated Piping Heat Loss and Surface Temperature

Nominal Pipe Size (mm)

Insulation Thickness (mm)

Heat Loss (W/m)

Surface Temperature

(°C) DN15 25 7.7 20 DN20 25 9.6 21 DN25 25 9.6 21 DN32 25 12.5 21 DN40 25 12.5 21 DN50 or less 13a 23.1 or less 23 DN50 25 15.4 21 DN65 38 11.5 19 DN80 38 15.4 20 DN100 38 18.3 21 DN150 38 26.0 21 DN200 38 30.8 21 DN250 38 36.5 21

Note: Figures based on average ambient temperature of 18°C and annual average wind speed of 12 km/h.

a Uncirculating hot water runout branches only.

Table 6 Heat Loss from Various Size Tanks with Various Insulation Thicknesses

Insulation Thickness

(in.)Tank Size

(gal)

Approx. Energy Loss from Tank at Hot Water

Temperature 140°F (Btu/h)a

1 50 4681 100 7362 250 7593 500 7593 1000 1273

Source: From Sheet Metal and Air Conditioning Contractors National Association (SMACNA) Table 2 data.

a For unfired tanks, federal standards limit the loss to no more than 6.5 Btu/h/ft2 of tank surface.

Table 6(M) Heat Loss from Various Size Tanks with Various Insulation Thicknesses

Insulation Thickness

(mm)Tank Size

(L)

Approx. Energy Loss from Tank at Hot Water Temperature 60°C (W)a

25.4 200 13725.4 400 21650.8 1000 22276.2 2000 22276.2 4000 373

Source: From Sheet Metal and Air Conditioning Contractors National Association (SMACNA) Table 2 data.

a For unfired tanks, federal standards limit the loss to no more than 1.9 W/m2 of tank surface.



The hot water return circulating pump is selected based on the required hot water return flow rate (in gpm [L/sec]), calculated using Equation 2, and the system’s pump head. The pump head is nor-mally determined by the friction losses through only the hot water return piping loops and any losses through balancing valves. The hot water return piping friction losses usually do not include the friction losses that occur in the hot water supply piping. The reason for this is that the hot water return circulation flow is needed only to keep the hot water supply system up to the desired temperature when there is no flow in the hot water supply piping. When people use the hot water at the fixtures, there is usually sufficient flow in the hot water supply piping to keep the system hot water supply piping up to the desired temperature without help from the flow in the hot water return piping.

The only exception to the rule of ignoring the friction losses in the hot water supply piping is a situation where a hot water return pipe is connected to a relatively small hot water supply line. “Relatively small” here means any hot water supply line that is less than one pipe size larger than the hot water return line. The problems cre-ated by this condition are that the hot water supply line will add additional friction to the head of the hot water circulating pump, and the hot water circulating pump flow rate can deprive the last plumbing fixture on this hot water supply line from obtaining its required flow. It is recommended, therefore, that in such a situation the hot water supply line supplying each hot water return piping connection point be increased to prevent these potential problems, i.e., use ¾ in. (DN22) hot water supply piping and ½ in. (DN15) hot water return piping, or 1 in. (DN28) hot water supply piping and ¾ in. (DN22) hot water return piping, etc.

When selecting the hot water circulating pump’s head, the designer should be sure to calculate only the restrictions encoun-tered by the circulating pump. A domestic hot water system is nor-mally considered an open system (i.e., open to the atmosphere). When the hot water circulating pump is operating, however, it is assumed that the piping is a closed system. Therefore, the designer should not include static heads where none exists. For example, in Figure 1, the hot water circulating pump has to overcome only the friction in the hot water return piping not the loss of the static head pumping the water up to the fixtures because in a closed system the static head loss is offset by the static head gain in the hot water return piping.

hOT WaTeR CIRCULaTINg PUmPsMost hot water circulating pumps are of the centrifugal type and are available as either in-line units for small systems or base-mounted units for large systems. Because of the corrosiveness of hot water systems, the pumps should be bronze, bronze fitted, or stainless steel. Conventional, iron bodied pumps, which are not bronze fitted, are not recommended.

CONTROL fOR hOT WaTeR CIRCULaTINg PUmPsThere are three major methods commonly used for controlling hot water circulating pumps: manual, thermostatic (aquastat), and time clock control. Sometimes more than one of these methods are used on a system.1. A manual control runs the hot water circulating pump contin-

uously when the power is turned on. A manual control should be used only when hot water is needed all the time, 24 h a day, or during all the periods of a building’s operation. Otherwise, it is not a cost-effective means of controlling the circulating pump because it will waste energy.

Note: The method for applying the “on demand” concept for controlling the hot water circulating pump is a manual control.

It can be used very successfully for residential and commercial applications.2. A thermostatic aquastat is a device that is inserted into the

hot water return line. When the water in the hot water return system reaches the distribution temperature, it shuts off the circulating pump until the hot water return system tempera-ture drops by approximately 10°F [5.5°C]. With this method, when there is a large consumption of hot water by the plumb-ing fixtures, the circulating pump does not operate.

3. A time clock is used to turn the pump on during specific hours of operation when people are using the fixtures. The pump would not operate, for example, at night in an office building when nobody is using the fixtures.

4. Often an aquastat and a time clock are used in conjunction so that during the hours a building is not operating the time clock shuts off the circulating pump, and during the hours the building is in use the aquastat shuts off the pump when the system is up to the desired temperature.

aIR eLImINaTIONIn any hot water return circulation system it is very important that there be a means of eliminating any entrapped air from the hot water return piping. Air elimination is not required in the hot water supply piping because the discharge of water from the fixtures will eliminate any entrapped air. If air is not eliminated from the hot water return lines, however, it can prevent the proper circulation of the hot water system. It is imperative that a means of air elimi-nation be provided at all high points of a hot water return system. The plumbing engineer must always give consideration to precisely where the air elimination devices are to be located and drained. For example, they should not be located in the unheated attics of build-ings in cold climates. If the plumbing engineer does not consider the location of these devices and where they will drain, the result may be unsightly piping in a building or extra construction costs.

INsULaTIONThe use of insulation is very cost-effective. It means paying one time to save the later cost of significant energy lost by the hot water supply and return piping system. Also, insulation decreases the stresses on the piping due to thermal expansion and contraction caused by changes in water temperature. Furthermore, the proper use of insulation eliminates the possibility of someone getting burned by a hot, uninsulated water line. See Table 5 for the surface tempera-tures of insulated lines (versus 140°F [60°C] for bare piping).

It is recommended that all hot water supply and return piping be insulated. This recommendation exceeds some code requirements. See Table 4 for the minimum required insulation thicknesses for all systems.

If the insulated piping is installed in a location where it is sub-jected to rain or other water, the insulation must be sealed with a watertight covering that will maintain its tightness over time. Wet insulation not only does not insulate, it also releases considerable heat energy from the hot water piping, thus wasting energy. Fur-thermore, the insulation on any outdoor lines that is not sealed watertight can be plagued by birds or rodents, etc., pecking at the insulation to use it for their nests. In time, the entire hot water supply and/or return piping will have no insulation. Such bare hot water supply and/or return piping will waste considerable energy and can seriously affect the operation of the hot water system and water heaters.

The minimum required insulation thicknesses given in Table 4 are based on insulation having thermal resistivity (R) in the range of 4.0 to 4.6 ft2 × h × (°F/Btu) × in. (0.028 to 0.032 m2 • [°C/W] • mm) on a flat surface at a mean temperature of 75°F (24°C). Minimum insula-




tion thickness shall be increased for materials having R values less than 4.0 ft2 × h × (°F/Btu) × in. (0.028 m2 • [°C/W] • mm) or may be reduced for materials having R values greater than 4.6 ft2 × h × (°F/Btu) × in. (0.032 m2 • [°C/W] • mm).1. For materials with thermal resistivity greater than 4.6

ft2 × h × (°F/Btu) × in. (0.032 m2 • [°C/W] • mm), the minimum insulation thickness may be reduced as follows:

4.6 × Table 4 thickness = New minimum thicknessActual R

( 0.032 • Table 4 thickness = New minimum thickness)Actual R2. For materials with thermal resistivity less than 4.0 ft2 × h × (°F/

Btu) × in. (0.028 m2 • [°C/W] • mm), the minimum insulation thickness shall be increased as follows:

4.0 × Table 4 thickness = New minimum thickness)Actual R

( 0.028 • Table 4 thickness = New minimum thickness)Actual R

CONCLUsIONIn conclusion, an inappropriate hot water recirculation system can have serious repercussions for the operation of the water heater and the sizing of the water heating system. In addition, it can cause the wastage of vast amounts of energy, water, and time. Therefore, it is incumbent upon the plumbing designer to design a hot water recirculation system so that it conserves natural resources and is in accordance with the recommendations given in this chapter.

BIBLIOgRaPhy1. American Society of Heating, Refrigerating, and Air Condi-

tioning Engineers. 1993. Pipe sizing. Chapter 33 in Fundamen-tals Handbook.

2. American Society of Heating, Refrigerating, and Air Condi-tioning Engineers. 1993. Thermal and water vapor transmis-sion data. Chapter 22 in Fundamen tals Handbook.

3. American Society of Heating, Refrigerating, and Air Condi-tioning Engineers. 1995. Service water heating. Chapter 45 in Applications Handbook.

4. American Society of Heating, Refrigerating, and Air Con-ditioning Engineers. Energy conservation in new build-ing design. ASHRAE Standards, 90A–1980, 90B–1975, and 90C–1977.

5. American Society of Heating, Refrigerating, and Air Condi-tioning Engineers. Energy efficient design of new low rise residential buildings. ASHRAE Standards, 90.2–1993.

6. American Society of Heating, Refrigerating, and Air Condi-tioning Engineers. New information on service water heating. Technical Data Bulletin. Vol. 10, No. 2.

7. American Society of Mechanical Engineers. Plumbing fixture fittings. ASME A112.18.1M–1989.

8. American Society of Plumbing Engineers. 2000. Cold water systems. Chapter 5 in ASPE Data Book, Volume 2.

9. American Society of Plumbing Engineers. 1989. Piping sys-tems. Chapter 10 in ASPE Data Book.

10. American Society of Plumbing Engineers. 1989. Position paper on hot water temperature limitations.

11. American Society of Plumbing Engineers. 1989. Service hot water systems. Chapter 4 in ASPE Data Book.

12. American Society of Plumbing Engineers. 1990. Insulation. Chapter 12 in ASPE Data Book.

13. American Society of Plumbing Engineers. 1990. Pumps. Chap-ter 11 in ASPE Data Book.

14. American Society of Plumbing Engineers. 2000. Energy con-servation in plumbing systems. Chapter 7 in ASPE Data Book, Volume 1.

15. American Water Works Association. 1985. Internal corrosion of water distribution systems. Research Foundation coopera-tive research report.

16. Cohen, Arthur. Copper Development Association. 1978. Copper for hot and cold potable water systems. Heating/Piping/Air Conditioning Magazine. May.

17. Cohen, Arthur. Copper Development Association. 1993. His-torical perspective of corrosion by potable waters in building systems. Paper no. 509 presented at the National Association of Corrosion Engineers Annual Conference.

18. Copper Development Association. 1993. Copper Tube Hand-book.

19. International Association of Plumbing and Mechanical Offi-cials. 1985. Uniform Plumbing Code Illustrated Training Manual.

20. Konen, Thomas P. 1984. An experimental study of competing systems for maintaining service water temperature in residen-tial buildings. In ASPE 1984 Convention Proceedings.

21. Konen, Thomas P. 1994. Impact of water conservation on interior plumbing. In Technical Proceedings of the 1994 ASPE Convention.

22. Saltzberg, Edward. 1988. The plumbing engineer as a forensic engineer. In Technical Proceedings of the 1988 ASPE Convention.

23. Saltzberg, Edward. 1993. To combine or not to combine: An in–depth review of standard and combined hydronic heat-ing systems and their various pitfalls. Paper presented at the American Society of Plumbing Engineers Symposium, Octo-ber 22–23.

24. Saltzberg, Edward. 1996. The effects of hot water circulation systems on hot water heater sizing and piping systems. Tech-nical presentation given at the American Society of Plumbing Engineers convention, November 3–6.

25. Saltzberg, Edward. 1997. In press. New methods for analyzing hot water systems. Plumbing Engineer Magazine.

26. Saltzberg, Edward. 1997. In press. Prompt delivery of hot water at fixtures. Plumbing Engineer Magazine.

27. Sealine, David A., Tod Windsor, Al Fehrm, and Greg Wilcox. 1988. Mixing valves and hot water temperature. In Technical Proceedings of the 1988 ASPE Convention.

28. Sheet Metal and Air Conditioning Contractors National Asso-ciation. 1982. Retrofit of Building Energy Systems and Processes.

29. Steele, Alfred. Engineered Plumbing Design. 2d ed.30. Steele, Alfred. 1988. Temperature limits in service hot water

systems. In Technical Proceedings of the 1988 ASPE Convention.31. Wen-Yung, W. Chan, and Milton Meckler. 1983. Pumps and

pump systems. In American Society of Plumbing Engineers Handbook.



about this issue’s articlethe december 2007 continuing education article is

“recirculating domestic Hot Water Systems,” Chapter 14 of Domestic Water Heating Design Manual, Second edition.

this chapter addresses the criteria for establishing an acceptable time delay in delivering hot water to fixtures and the limitations of the length between a hot water re-circulation system and plumbing fixtures. it also discusses the temperature drop across a hot water supply system, types of hot water recirculation system, and pump selec-tion criteria, and gives extensive information on the insulation of hot water supply and return piping.

you may locate this article at www.psdmagazine.org. read the article, complete the following exam, and sub-mit your answer sheet to the aSPe office to potentially receive 0.1 Ceu.

PSd

143

Continuing education from Plumbing Systems & DesignHaig demergian, Pe, CPd

Ce Questions—“recirculating domestic Hot Water Systems” (PSd 143)1. If the balancing valve is also used as the shutoff valve, the

balancing valve must have a ___________.a. long stemb. flanged endc. memory stopd. none of the above

2. The water content of 1-inch Type L copper pipe is __________ gal/ft.a. 0.060b. 0.052c. 0.043d. 0.039

3. hot water recirculation systems with circulating pumps are installed in large buildings to __________.a. maintain constant hot water pressure at fixturesb. provide a reasonably prompt hot water supply to fixturesc. both of the aboved. neither of the above

4. The approximate heat loss of a tank with 1-inch insulation holding 100 gallons of 140°f hot water is __________ Btu/h.a. 736, b. 137, c. 468, d. 1,273

5. The minimum recommended fiberglass pipe insulation thickness for a 2-inch diameter potable hot water pipe is __________.a. ¾ inchb. 1 inchc. 1½ inchesd. 2 inches

6. The approximate heat loss of 1-inch copper pipe with 1-inch insulation (assuming 65°f ambient temperature) is __________ Btu/h per foot.a. 8, b. 10, c. 12, d. 14

7. The total estimated heat loss of 520 feet of 1½-inch copper pipe, with 1-inch fiberglass insulation, is __________ Btu/h.a. 6,000, b. 6,320, c. 6,760, d. 7,520

8. The approximate time to deliver hot water to a 1.5-gpm fixture 25 feet from the water heater, using ¾-inch copper supply pipe, is __________ seconds.a. 25, b. 30, c. 40, d. 50

9. The gpm of a hot water circulating pump for a system with a total calculated heat loss of 10,000 Btu/h and 5°f allowable temperature drop between hot water supply and return is __________.a. 3, b. 4, c. 7, d. 9

10. The heat required to raise 35 gpm from 50°f to 140°f is __________ Btu/h.a. 895,000b. 1,270,000c. 1,575,000d. 1,625,000

11. Why it is necessary to provide a pressure relief valve on potable hot water systems?a. to relieve the water, which expands during the heating

processb. to protect the water heater and piping from excessive

pressurec. both of the above d. neither of the above

12. automatic air vents for air elimination shall be installed on the high points of __________.a. hot water supply pipingb. hot water return pipingc. cold water supply pipingd. none of the above


now online!The technical article you must read to complete the exam is located at www.psdmagazine.org. Just click on “Plumbing Systems & Design Continuing Education Article and Exam” at the top of the page. The following exam and application form also may be downloaded from the website. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. If you earn a grade of 90 per-cent or higher on the test, you will be notified that you have logged 0.1 CEU, which can be applied toward CPD renewal or numerous regulatory-agency CE programs. (Please note that it is your responsi-bility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for three years.Note: In determining your answers to the CE questions, use only the material presented in the corresponding continuing education article. Using information from other materials may result in a wrong answer.



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PSD

140

Flow in Water Piping

ContinuingEducationfromPlumbing Systems & DesignKennethG.Wentink,PE,CPD,andRobertD.Jackson

JULY/AUGUST 2007

PSDMAGAZINE.ORG


Hydraulics can be defined as the study of the principles and laws that govern the behavior of liquids at rest or in motion.Hydrostatics is the study of liquids at rest and hydrokinetics is the study of liquids in motion.

Although this text deals exclusively with water, all the data developed can be applied to any liquid.

Physical ProPerties of WaterThe weight of water, or its density, varies with its temperature and purity. Water has its greatest specific weight (weight per cubic foot) at a temperature of 39.2°F. If this phenomenon did not occur, lakes would start freezing from the bottom up instead of from the top down. Table 1 tabulates densities of pure water at various tempera-tures. For the normal range of tempera-tures met in plumb-ing systems, the den-sity of water is very close to 62.4 lbm/ft3 and this value can be used for all calcula-tions without any significant error.

Viscosity can be defined as the inter-nal friction, or inter-nal resistance, to the relative motion of fluid particles. It can also be defined as the property by which fluids offer a resistance to a change of shape under the action of an external force. Viscosity varies greatly from one liquid to another. It approaches the condi-tions of a solid for highly viscous liquids and approaches a gas for the slightly viscous liquids. Viscosity decreases with rising tem-peratures. For example, #6 oil is a solid at low temperatures and begins to flow as it is heated.

Water is perfectly elastic, compressing when pressure is imposed and returning to its original condition when the pres-sure is removed. The compressibility of water may be expressed as 1/K, where K is the coefficient of compressibility and is equal to 43,200,000 lb/ft2. It can be seen that if a pressure of 100 lb/ft2 were applied, the volumetric change would be 100∕43,200,000. The change is of such negligible significance that water is always treated as incompressible for all calculations in plumbing design.

The temperature at which water boils varies with the pressure to which it is subjected. At sea level—14.7 psi—water boils at 212°F. At an elevation above sea level, where the atmospheric pressure is less than 14.7 psi, water will boil at a lower tem-perature. In a closed system, such as that found in the domestic hot water system where the pressure is generally around 50 psi above atmospheric pressure, the water will not boil until a tem-perature of 300°F is reached.

tyPes of floWWhen water is moving in a pipe, two types of flow can exist. One type is known by the various names of streamline, laminar, or viscous. The second is called turbulent flow. At various viscosi-ties (various temperatures), there is a certain critical velocity for every pipe size above which turbulent flow occurs and below which laminar flow occurs. This critical velocity occurs within a range of Reynolds numbers from approximately 2100 to 4000. Reynolds formula is:

Equation 1Re = DV ρ

µgc

where Re = Reynolds number, dimensionless D = Pipe diameter, ft V = Velocity of flow, ft/sec ρ = Density, lbm/ft3

µ = Absolute viscosity, lbf · sec/ft2

gc = Gravitational constant, 32.2 lbm·ft/lbf·sec2

Within the limits of accuracy required for plumbing design, it can be assumed that the critical velocity occurs at a Reynolds number of 2100. In laminar flow, the roughness of the pipe wall has a negligible effect on the flow but the viscosity has a very significant effect. In turbulent flow, the viscosity has an insignif-icant effect but the roughness of the pipe wall has a very marked effect on the flow.

Very rarely is a velocity of less than 4 ft/sec employed in plumbing design. The Reynolds number for a 3 in. pipe and a velocity of flow of 4 ft/sec would be

Re =(0.250ft)(4ft/sec)(62.4lbm/ft3) = 82,500

(2.35 × 10–5 lbf·sec/ft2)(32.2 lbm·ft/lbf·sec2

(which is well above the critical number of 2,100)

It can be seen that all plumbing design is with turbulent flow and only when very viscous liquids or extremely low velocities are encountered does the plumbing engineer deal with laminar flow. Critical velocities of ½, 1, and 2-in. pipe at 60°F are 0.61, 0.31, and 0.15 ft/sec, respectively, and at 140°F they are 0.25, 0.13, and 0.06 ft/sec, respectively.

Velocity of floWWhen the velocity of flow is measured across the section of pipe from the center to the wall, it is found that there is a variation in the velocity, with the greatest velocity at the center and a mini-mum velocity at the walls. The average velocity for the entire cross-section is approximately 84% of the velocity as measured at the center. The plumbing engineer is concerned only with the average velocity, and all formulas are expressed in average velocity. Whenever and wherever the term velocity is used, it is the average velocity of flow that is meant.

Since water is incompressible within the range of pressures met in plumbing design, a definite relationship can be expressed between the quantity flowing past a given point in a given time

Flow in Water Piping

Reprinted from Engineered Plumbing Design II, Chapter 11: “Flow in Water Piping,” by A. Calvin Laws, PE, CPD.© American Society of Plumbing Engineers.

Table 1 Density of Pure Water at Various Temperatures

Temperature °F

Density lbm/ft3

Temperature °F

Density lbm/ft3

32 62.416 100 61.98835 62.421 120 61.71939.2 62.424 140 61.38640 62.423 160 61.00650 62.408 180 60.58660 62.366 200 60.13570 62.300 212 59.84380 62.217

Plumbing Systems & Design JULY/AUGUST 2007 PSDMAGAZINE.ORG



and the velocity of flow. This can be expressed as (Equation 3-2):

Q = AVwhere Q = quantity of flow (volumetric flow rate), ft3/sec A = cross-sectional area of flow, ft2

V = velocity of flow, ft/sec

The units employed in this flow formula are inconvenient for use in plumbing design. The plumbing engineer deals in gallons per minute and inches for pipe sizes. Converting to these terms, the flow rate becomes (Equation 8-8):

q = 2.448 d2Vwhere q = quantity of flow (flow rate), gpm d = diameter of pipe, in. V = velocity of flow, ft/sec

Potential energyOne of the most fundamental laws of thermodynamics is that energy can be neither created nor destroyed; it can only be con-verted from one form to another. The energy of a body due to its elevation above a given level is called its potential energy in relation to that datum. Work had to be performed to raise the body to that elevation and this work is equal to the product of the weight of the body and the height it was raised. This can be expressed as:

Equation 2EP = w h = mgh

gc

where EP = potential energy, ft lbf w = weight of the body, lbf h = height raised, ft g = gravitational acceleration, 32.2 ft/s2

gc = gravitational constant, 32.2 lbm·ft/lbf·s2

When the weight is equal to 1 lb the for-mula becomes

Equation 3EP = hg

gc

where EP = potential energy per pound weight

Kinetic energyThe energy of a body due to its motion is called kinetic energy and is equal to one-half its mass and the square of its velocity. Mass is equal to the weight of the body divided by its acceleration imposed by gravity.

Equation 4m =

wgc

gc

Equation 5

EK = ½ × wgc × V2

= w × V2gc gc 2g

where EK = kinetic energy, ft lbf w = weight of body, lbf m = mass of the body, lbm

g = gravitational acceleration, 32.2 ft/sec2

gc = gravitational constant, 32.2 lbm·ft/lbf·sec2

V = velocity, ft/sec

When the body weighs 1 lb the formula becomes

Equation 6EK = V2

2gc

where EK = kinetic energy per pound weight

static headAt any point below the surface of water that is exposed to atmo-spheric pressure, the pressure (head) is produced by the weight of the water above that point. The pressure is equal and effective in all directions at this point and is proportional to the depth below the surface. This pressure is variously called static head, static pressure, hydrostatic head, or hydrostatic pressure. It is the measure of the potential energy. Because pressure is a function of the weight of the water, it is possible to convert the static head expressed as feet of head into pounds per square inch. (See Table 2.)

The pressure developed by the weight of a column of water 1 in.2 in cross-sectional area and h ft high may be expressed as

Equation 7p = γ × h144

where p = pressure, lbf/in2 γ =specificweightofwater,lbf/ft3

h = static head, ft

At 50°F, the pressure expressed in pounds per square inch for a 1-ft column of water is then:

Table 2 Heads of Water in Feet Corresponding to Pressure in Pounds per Square InchPSI 0 1 2 3 4 5 6 7 8 9

0 2.3 4.6 6.9 9.2 11.6 13.9 16.2 18.5 20.810 23.1 25.4 27.7 30.0 32.3 34.7 37.0 39.3 41 .6 43.920 46.2 48.5 50.8 53.1 55.4 57.8 60.1 62.4 64.7 67.030 69.3 71.6 73.9 76.2 78.5 80.9 83.2 85.5 87.8 90.140 92.4 94.7 97.0 99.3 101.6 104.0 106.3 108.6 110.9 113.250 115.5 117.8 120.1 122.4 124.7 127.1 129.4 131.7 134.0 136.360 138.6 140.9 143.2 145.5 147.8 150.2 152.5 154.8 157.1 159.470 161.7 164.0 166.3 168.6 170.9 173.3 175.6 177.9 180.2 182.580 184.8 187.1 189.4 191.7 194.0 196.4 198.7 201.0 203.3 205.690 207.9 210.2 212.5 214.8 217.1 219.5 221.8 224.1 226.4 228.7

100 231.0 233.3 235.6 237.9 240.2 242.6 244.9 247.2 249.5 251.8110 254.1 256.4 258.7 261.0 263.3 265.7 268.0 270.3 272.6 274.9120 277.2 279.5 281.8 284.1 286.4 288.8 291.1 293.4 295.7 298.0130 300.3 302.6 304.9 307.2 309.5 311.9 314.2 316.5 318.8 321.1140 323.4 325.7 328.0 330.3 332.6 335.0 337.3 339.6 341.9 344.2150 346.5 348.8 351.1 353.4 355.7 358.1 360.4 362.7 365.0 367.3160 369.6 371.9 374.2 376.5 378.8 381.2 383.5 385.8 388.1 390.4170 392.7 395.0 397.3 399.6 401.9 404.3 406.6 408.9 411.2 413.5180 415.8 418.1 420.4 422.7 425.0 427.4 429.7 432.0 434.3 436.6190 438.9 441.2 443.5 445.8 448.1 450.5 452.8 455.1 457.4 459.7200 462.0 464.3 466.6 468.9 471.2 473.6 475.9 478.2 480.5 482.8210 485.1 487.4 489.7 492.0 494.3 496.7 499.0 501.3 503.6 505.9220 508.2 510.5 512.8 515.1 517.4 519.8 522.1 524.4 526.7 529.0230 531.3 533.6 535.9 538.2 540.5 542.9 545.2 547.5 549.8 552.1240 554.4 556.7 559.0 561.3 563.6 566.0 568.3 570.6 572.9 575.2250 577.5 579.8 582.1 584.4 586.7 589.1 591.4 593.7 596.0 598.3

Notes: 1. To use the chart, find the point corresponding to the specific pressure (psi) by adding incremental values in the top line to the base values in the extreme left column. For example, to find head in ft. corresponding to 25 psi, follow the line of figures to the right of 20 psi and read 57.8 ft under 5 psi. 2. Head values in the body of the chart were calculated by multiplying psi by 2.31. To convert ft of head to psi, multiply by 0.433, or use the chart in reverse.

JULY/AUGUST 2007 Plumbing Systems & Design


p = 62.408 × 1 = 0.433 lbf/in2144

Conversely, the height of a column of water that will impose a pressure of 1 lb/in.2 is

h = p × 144γ

h = 1 × 144 = 2.31 ft62.408To convert from feet of head to pounds per square inch, mul-

tiply the height by 0.433. To convert pounds per square inch to feet of head, multiply the pounds per square inch by 2.31.

Velocity headIn a piping system with the water at rest, the water has poten-tial energy. When the water is flowing it has kinetic energy as well as potential energy. To cause the water to flow some of the available potential energy must be converted to kinetic energy. The decrease in the potential energy, or static head, is called the velocity head.

In a freely falling body, the body is accelerated by the action of gravity at a rate of 32.2 ft/sec2. The height of the fall and the velocity at any moment may be expressed as:

Equation 8h = gt2

2

Equation 9V = gt

or t = Vg

where h = velocity head, ft t = time, sec g = gravitational acceleration, 32.2 ft/sec2

V = velocity, ft/secSubstituting t = V/g in the first equation,

h = g

× V2

2 g2

Equation 10

h = V2

2gThe foregoing illustrates the conversion of the

potential energy of a body (static head) due to its height into kinetic energy (velocity head). The velocity head, V2/2g, is a measure of the decrease in static head expressed in feet of column of water.

Bernoulli’s theoremAs previously stated, energy can be neither created nor destroyed. Bernoulli developed an equation to express this conservation of energy as it is applied to a flowing liquid. The liquid is assumed to be fric-tionless and incompressible.

Equation 11Zg +

Pgc + V2= ETgc ρg 2gc

where ET = total energy ft·lbf/lbm Z = height of point above datum, ft P = pressure, lbf/ ft2

ρ = density, lbm/ft3 V = velocity, ft/sec g = gravitational acceleration, 32.2 ft./sec2

gc = gravitational constant, 32.2 lbm·ft/lbf·sec2

The term Pgc/ρg is equal to the static head or height of the liquid column. Substituting in the equation it becomes

Equation 12Zg + h + V2

= ETgc 2gc

For any two points in a system, we may then write:

Equation 13Z1g

+ h1 +V1

2

= Z2g

+ h2 +V2

2

gc 2gc gc 2gc

Figure 1 illustrates the application of this equation.

frictionWhen water flows in a pipe, friction is produced by the rubbing of water particles against each other and against the walls of the pipe. This friction generates heat, which is dissipated in the form of a rise in the temperature of the water and the piping. This temperature rise in plumbing systems is insignificant and can safely be ignored in plumbing design. It requires a potential energy of 778 ft-lbf to raise 1 lb of water 1°F. The friction pro-duced by flowing water also causes a pressure loss along the line of flow, which is called friction head. By utilizing Bernoulli’s equation this friction head loss can be expressed as:

Figure 11-1 Bernoulli's Theorem (Disregarding Friction)

Z1g + h1 +V1

2

= Z2g + h2 +

V22

gc 2gc gc 2gc


CONTINUING EDUCATION: Flow in Water Piping


hF = [Z1g+ h1 +

V12 ] - [ Z2g

+ h2 +V2

2 ]gc 2gc gc 2gc

floW from outletsExperiments to determine the velocity of flow from an outlet in the side of an open tank were performed by Toricelli in the 17th century. The result of these experi-ments was expounded in the theorem: “Except for minor frictional effects, the velocity is the same as if the fluid had fallen freely from the surface through a vertical dis-tance to the outlet.” This can be expressed as:

Equation 15V = √2gh

It is graphically shown in Figure 2.

If friction, size, and shape of the opening and entrance losses are disregarded, the ideal velocity is the same as the maximum velocity and is equal to the velocity attained by free fall. The actual velocity, however, is always less than the ideal. All the factors, previously ignored, when taken into consideration can be expressed as the coef-ficient of discharge, CD. The actual velocity can then be written:

Equation 16V = CD √2gh

For most outlets encountered in a plumbing system an average coefficient of discharge of 0.67 can be safely applied.

floW in PiPingThe velocity of flow at any point in a system is due to the total energy at that point. This is the sum of the potential and kinetic energy, less the friction head loss. The static head is the potential energy, but some of it was con-verted to kinetic energy to cause flow and some of it was used to overcome friction. It is for these reasons that the pressure during flow is always less than the static pressure. The pressure measured at any point while water is flowing is called the flow pressure. This is the pressure that is read on a pressure gauge installed in the piping.

The kinetic energy of water flowing in a plumbing system is extremely small. Very rarely is the design velocity for water flow in plumbing systems greater than 8 ft/sec. The kinetic energy (velocity head) at this velocity is V2/2g or 82∕64.4. This is equal to 1 ft or 0.433 psi, which is less than 0.5 psi. It can be seen that such an insignificant pressure can be safely ignored in all calcu-lations. The maximum rate of discharge from an outlet can now be determined from the flow pressure and the diameter of the outlet (using Equations 8-2 to 8-5):

qD = CD q1

qD = CD × 2.448 d2V1

qD = CD × 2.448d2 √2ghqD = CD × 19.65d2 √h or

Equation 17qD = CD × 29.87d2 √p

where qD = actual quantity of discharge, gpm q1 = ideal quantity of discharge, gpm CD = coefficient of discharge, dimensionless

d = diameter of outlet, in. V1 = ideal velocity, ft/sec h = flow pressure, ft p = flow pressure, psi

If 0.67 is used for the coefficient of discharge, then, per Equa-tion 6-1,

qD = 13.17d2 √hand

Equation 18qD = 20d2 √p

friction in PiPingAs stated previously, whenever flow occurs, there is a continu-ous loss of pressure along the piping in the direction of flow. The amount of this head loss because of friction is affected by

1. Density and temperature of the fluid2. Roughness of the pipe3. Length of run4. Velocity of the fluid

Experiments have demonstrated that the friction head loss is inversely proportional to the diameter of the pipe, proportional to the roughness and length of the pipe, and varies approxi-

Figure 11-2 Toricelli's Theorem



mately with the square of the velocity. Darcy expressed this rela-tionship as:

h = fLV2or

D × 2gEquation 19

p = ρfLV2

144D × 2gcwhere h = friction head loss, ft p = friction head loss, lbf/in2

ρ = density of fluid, lbm/ft3 f = coefficient of friction, dimensionless L = length of pipe, ft D = diameter of pipe, ft V = velocity of flow, ft/sec gc = gravitational constant, 32.2 lbm ft/lbf sec2

Values for the coefficient of friction are given in Table 3.It can be seen from Table 3 that steel pipe is much rougher

than brass, lead or copper. It follows that there will be a greater head loss in steel pipe than in the other material.

For ease of application for the plumbing engineer, the for-mula for friction head loss can be reduced to a simpler form. Assuming an average value for the coefficient of friction of 0.02 for brass and copper and 0.04 for steel, the formula becomes:

For brass and copper

Equation 20

h = 0.000623q2 × Ld5

Equation 21

p = 0.00027q2 × Ld5

and for steel

Equation 22

h = 0.00124q2 × Ld5

Equation 23

p = 0.00539q2 × Ld5

These formulas can be rearranged in another useful form:

For brass and copper

Equation 24

q = 40.1 d2½(h)½

LEquation 25

q = 60.8 d2½(p)½

Land for steel

Equation 26

q = 28.3 d2½(h)½

LEquation 27

q = 43.0 d2½(p)½

Lwhere q = quantity of flow, gpm d = diameter of pipe, in. h = pressure, ft p = pressure, psi L = length of pipe, ft

The terms h/L and p/L represent the loss of head due to fric-tion for 1 ft of pipe length and is called the uniform friction loss. Values of d2½ for various diameters of pipe and various materials are given in Table 4.

In all water flow formulas, the term L (length of run in feet) is always the equivalent length of run (ELR).Every fitting and valve imposes more frictional resistance than the pipe itself.To take this additional friction head loss into account, the fitting or valve is converted to an equivalent length of pipe of the same size that will impose an equal friction loss, e.g., a 4-in. elbow is equivalent to 10 ft of 4-in. pipe.Thus, if the measured length of run of 4-in. piping with one elbow is 15 ft, then the equiva-lent length of run is 15 + 10 = 25 ft.The length of pipe measured

Table 4 Values of d2½

Nominal Size, In.

Brass or Copper Pipe

Copper Type K

Copper Type L

Galvanized Iron or Steel

½ 0.31 0.20 0.22 0.31¾ 0.61 0.48 0.55 0.621 1.16 0.99 1.06 1.131¼ 2.19 1.73 1.80 2.241½ 3.24 2.67 2.78 3.292 6.17 5.37 5.55 6.142½ 9.88 9.25 9.54 9.583 16.41 14.41 14.87 16.484 32.00 29.23 30.13 32.53

Table 5 Equivalent Pipe Length for Valves and Fittings

Nominal Pipe Size

inches

Gate Valve Full

Open

Angle Valve Full

Open

Globe Valve Full

Open

Swing Check Full

Open 45°

Elbow

Long Sweep

Elbow or Run of Tee

Std. Elbow

Std. Tee Thru Side

Outlet½ 0.35 9.3 18.6 4.3 0.78 1.11 1.7 3.3¾ 0.44 11.5 23.1 5.3 0.97 1.4 2.1 4.21 0.56 14.7 29.4 6.8 1.23 1.8 2.6 5.31¼ 0.74 19.3 38.6 8.9 1.6 2.3 3.5 7.01½ 0.86 22.6 45.2 10.4 1.9 2.7 4.1 8.12 1.10 29.0 58.0 13.4 2.4 3.5 5.2 10.42½ 1.32 35.0 69.0 15.9 2.9 4.2 6.2 12.43 1.60 43.0 86.0 19.8 3.6 5.2 7.7 15.54 2.10 57.0 113.0 26.0 4.7 6.8 10.2 20.35 2.70 71.0 142.0 33.0 5.9 8.5 12.7 25.46 3.20 85.0 170.0 39.0 7.1 10.2 15.3 31.08 4.30 112.0 224.0 52.0 9.4 13.4 20.2 40.0

Table 3 Average Values for Coefficient of Friction, fNominal

Pipe Size, in.Brass, Copper,

or LeadGalvanized

Iron or Steel½ 0.022 0.044¾ 0.021 0.0401 0.020 0.0381¼ 0.020 0.0361½ 0.019 0.0352 0.018 0.0332½ 0.017 0.0313 0.017 0.0314 0.016 0.030


CONTINUING EDUCATION: Flow in Water Piping


along the centerline of pipe and fittings is the developed length.Table 5 shows equivalent lengths of pipe for valves and fittings of various sizes. Note that the larger the pipe size, the more significant the equivalent length of run becomes. In the design phase of piping systems, the size of the piping is not known and the equivalent lengths cannot be accurately determined. A rule of thumb that has worked exceptionally well is to assume 50% of the developed length as an allowance for fittings and valves. Once the sizes are determined, the accuracy of the assumption can be checked.

All equipment imposes a friction head loss and must be care-fully considered in the design and operation of a system. The pressure drop through any piece of equipment can be obtained from the manufacturer. The knowledgeable engineer is care-ful to specify the maximum pressure drop he/she will permit through a piece of equipment.




AboutThisIssue’sArticleTheJuly/August2007continuingeducationarticleis“FlowinWaterPiping,”Chapter11ofEngineered Plumbing Design IIbyA.CalLaws,PE,CPD.

Thischapterdiscusseshydraulics,whichcanbedefinedasthestudyoftheprinciplesandlawsthatgovernthebehav-iorofliquidsatrestorinmotion,hydrostatics,thestudyofliquidsatrest,andhydrokinetics,orthestudyofliquidsinmotion.Althoughthistextdealsexclusivelywithwater,allthedatadevelopedcanbeappliedtoanyliquid.Thechapterdelvesintothephysicalpropertiesofwater,typesofflow,Bernoulli’sandToricelli’sTheorems,andfrictioninpipingastheyrelatetosizingpipingsystems.ItprovidescalculationsforfindingtheReynoldsnumber,velocityofflow,potentialandkineticenergy,pressure,velocityhead,andBernoulli’sTheorem,amongothers.

Youmaylocatethisarticleatwww.psdmagazine.org.Readthearticle,completethefollowingexam,andsubmityouranswersheettotheASPEofficetopotentiallyreceive0.1CEU.

PSD

140

ContinuingEducationfromPlumbing Systems & DesignKennethG.Wentink,PE,CPD,andRobertD.Jackson

CEQuestions—“FlowinWaterPiping”(PSD140)

1. The average coefficient of friction (f) in a -inch steel pipe is _________. a. 0.037b. 0.035c. 0.033d. 0.031

. Friction is created by the flow of water in piping. This friction generates _________.a. pressuredropb. pressureincreasec. heatd. noneoftheabove

. Number six () oil _________.a. isnotpartofthischapterb. isasolidatlowtemperaturesc. beginstoflowwhenheatedd. bandconly

. Water is _________.a. notcompressibleb. perfectlyelasticc. greatlycompressibled. noneoftheabove

. Experiments to determine the velocity of flow from an outlet were performed by _________ in the 1th century.a. Bernoullib. Reynoldsc. Toricellid. Hunter

. Velocity head (V/g) _________.a. isameasureofthedecreaseinstaticheadb. isofnoconsequencetotheplumbingengineerc. mustbeunderstoodtocontrolwaterhammerd. isresponsibleformostpipefittingfailures

. How much potential energy is required to raise 1 pound of water 1°F?a. 728ft-lbf,b. 778ft-lbf,c. 828ft-lbf,d. 878ft-lbf

8. The pressure at any point below the surface of water exposed to atmospheric pressure is referred to as ______.a. staticheadb. hydrostaticpressurec. specificpressured. aorb

9. What is the equivalent pipe length for a -inch fully open globe valve?a. 113.0b. 142.0c. 170.0d. 224.0

10. The critical velocity of water _________.a. in½-inch,1-inch,and2-inchpipeislessthan0.5fpsat

temperaturesof60°Fto140°Fb. isrepresentedbyaReynoldsnumberof82,500c. isRe=DVp/ugc

d. isgreaterthan20ft/secforallpipe10inchesandsmallerattemperaturesof60°Fto140°F

11. The static pressure is always _________ the pressure during flow.a. lessthanb. greaterthanc. thesameasd. noneoftheabove

1. Water in motion _________.a. hasuseditspotentialenergyb. hasonlykineticenergyc. hasbothkineticandpotentialenergyd. noneoftheabove


NowOnline!The technical article you must read to complete the exam is located

at www.psdmagazine.org. The following exam and application form also may be downloaded from the website. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. For most people, this process will require approximately one hour. If you earn a grade of 90 percent or higher on the test, you will be notified that you have logged 0.1 CEU, which can be applied toward the CPD renewal requirement or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for three years.


8 Plumbing Systems & Design JULY/AUGUST 2007 PSDMAGAZINE.ORG


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Appraisal QuestionsFlow in Water Piping (PSD 140)





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JULY/AUGUST 2007 Plumbing Systems & Design 9


psd

144

Fuel Gas Piping Systems

continuing education from Plumbing Systems & Designdiane m. wingard, cpd

JANUARY/FEBRUARY 2008

PSDMAGAZINE.ORG


LOW AND MEDIUM-PRESSURE NG SYSTEMSThis chapter describes fuel-gas systems on consumer sites from the property line to the final connection with the most remote gas appliance or piece of equipment. The system is intended to provide sufficient pressure and volume for all uses. Since NG is a nonrenew-able energy resource, the engineer should design for its efficient use. The direct utilization of NG is preferable to the use of electrical energy when electricity is obtained from the combustion of gas or oil. However, in many areas, the gas supplier and /or governmental agencies may impose regulations that restrict the use of natural gas. Refer to the chapter “Energy Conservation in Plumbing Systems” in Plumbing Engineering Design Handbook Volume 1 for information on appliance efficiencies and energy conservation recommenda-tions.

The composition, specific gravity, and heating value of NG (NG) vary depending on the well (or field) from which the gas is gathered. NG is a mixture of gases, most of which are hydrocarbons, and the predominant hydrocarbon is methane. Some natural gases contain significant quantities of nitrogen, carbon dioxide, or sulfur (usually as H2S). Natural gases containing sulfur or carbon dioxide are apt to be corrosive. These corrosive substances are usually eliminated by treatment of the NG before it is transmitted to the customers. Read-ily condensable petroleum gases also are usually extracted before the NG is put into the pipeline to prevent condensation during transmission. The physical properties of both NG and liquefied

petroleum gas (LPG) are given in Table 1. NG and LPG are colorless and odorless, so an additive is added to the gases to detect a leak.

GeneralNG is obtained from a franchised public utility obligated to provide gas to all who request this service. There are different types of ser-vices a utility may provide, each with a different cost. They include the following:1. Firm Service. This service provides constant supply of gas

under all conditions.2. Interruptible Service. This service allows the utility to stop gas

supply under certain conditions and proper notification and to start service when the conditions no longer exist. The most common reason for this interruption is when the ambient temperature falls below a predetermined point.

3. Light or Heavy Process Service. This service is provided for process or other industrial use. The quantity of gas must meet utility company requirements.

4. Commercial or Industrial Service. This type of service is used for heating and cooling loads for this class of building.

5. Transportation Gas Service. This is used when the gas is purchased directly from the producer (or wellhead) and not directly from the utility company. The gas actually is carried in the utility company mains, and there is a charge for this use.

There are many gases used as a fuel gas. Where easily and cheaply available, two major fuel gases, NG and LPG, are preferred. Other gases are used because of availability. For properties of gases com-

monly available throughout the world, refer to Table 2.

approvalsThe American Gas Association, the National Fire Protection Association, and the American National Standards Associa-tion do not approve, inspect, or certify installations, proce-dures, equipment, or materials. The acceptability of all such items must comply with the authority having jurisdiction (AHJ).

system operatinG pressureThe gas pressure in the piping system downstream of the meter is usually 5 to 14 in. (125 to 356 mm) of water column (wc). Under these conditions, good engineering practice limits the pressure losses in the piping to a range between 0.2 to 0.5 in. (5 to 13 mm) wc. However, local codes may dictate a more stringent pressure drop maximum; these should be consulted before the system is sized. Most appliances require approximately 3.5 in. (89 mm) wc. The designer must be aware that large appliances, such as boil-ers, may require high gas pressures to operate properly. Where appliances require high pressures or where long distribution lines are involved, it may be necessary to use higher pressures at the meter outlet to satisfy the appli-ance requirements or provide for greater pressure losses in the piping system, thereby allowing economy of pipe size. Systems often are designed with meter outlet pressures of 3 to 5 psi (20.7 to 34.5 kPa) and with pressure regula-tors to reduce the pressure for appliances as required. A

Fuel Gas Piping Systems

Reprinted from Plumbing Engineering Design Handbook, Volume 2: Plumbing Systems, Chapter 7: “Fuel Gas Piping Systems.” © American Society of Plumbing Engineers , 2005.

PropaneNatural gas (methane)

Formula C3H8 CH4

Molecular weight 44.097 16.402Melting (or freezing) point, °F – 305.84 – 300.54Boiling point, °F – 44 – 258.70Specific gravity of gas (air = 1.00) 1.52 0.60Specific gravity of liquid 60°F/60°F (water = 1.00) 0.588 0.30Latent heat of vaporization at normal boiling point, Btu/lb 183 245Vapor pressure, lb/in2, gauge at 60°F 92Pounds per gallon of liquid at 60°F 4.24 2.51Gallons per pound of liquid at 60°F 0.237Btu per pound of gas (gross) 21591 23000Btu per ft3 gas at 60°F and 30 in mercury 2516 1050 ±Btu per gallon of gas at 60°F 91547Cubic feet of gas (60°F, 30 in Hg)/gal of liquid 36.39 59.0Cubic feet of gas (60°F, 30 in Hg)/lb of liquid 8.58 23.6Cubic feet of air required to burn 1 ft3 gas 23.87 9.53Flame temperature, °F 3595 3416Octane number (isooctane = 100) 125Flammability limit in air, upper 9.50 15.0Flammability limit in air, lower 2.87 5.0

Table 1 Average Physical Properties of Natural Gas and Propane

2 Plumbing Systems & Design JANUARY/FEBRUARY 2008 PSDMAGAZINE.ORG



majority of times, the utility company will reduce the incoming pressure to a figure that is requested by the design engineer at the start of the project.

The maximum allowable operating pressure for NG piping sys-tems inside a building is based on NFPA 54: National Fuel Gas Code, except when approved by the AHJ or when insurance carriers have more limiting requirements. NG systems are not permitted to have more than 5 psig (34.5 kPa) unless all the following are met:

1. The AHJ will allow a higher pressure.2. The distribution piping is welded.3. Pipe runs are enclosed for protection and located in a venti-

lated place that will not allow gas to accumulate.4. The pipe is installed in areas only used for industrial pro-

cesses, research, warehouse, or mechanical equipment rooms.

The maximum LPG pressure of 20 psig (138 kPa) is allowed, pro-vided the building is used only for research or industrial purposes and is constructed in accordance with NFPA 58: Liquefied Petro-leum Gas Code, Chapter 7.

efficiencyThe difference between the input and the output of any equipment is the heat lost in the burner, the heat exchanger, and the flue gases. Water heating and space heating equipment are usually 75 to 85% efficient, and ratings are given for both input and output. Cooking and laundry equipment also is usually 75 to 85% efficient, and rat-ings are given for the input that take into consideration the internal losses. When only the output required for the appliance is known, it will be necessary to increase the volume of gas to account for the loss of efficiency.

codes and standardsThe local code in the area where the project is located is the primary code to be used. Often, this code refers to NFPA 54. Other codes and standards that may be applicable are ANSI/NFPA 30: Flam-mable and Combustible Liquids Code, ANSI/NFPA 58, ANSI Z83.3: Gas Utilization Equipment for Large Boilers, ANSI/UL 144: Pressure Regulating Valves for LPG, NFPA 88A: Standard for Parking Struc-tures, and American Gas Association standards. Insurance carriers such as Industrial Risk Insurers and FM Global also have standards, which may be in many respects stricter than the applicable code.

Gas metersMeters are required in all services. To achieve greatest accuracy, the pressure into the meter must be regulated. Requirements for various utilities differ regarding the placement and arrangement of the meter assembly. The assembly could consist of filters, valves, regulators, and relief valves. It could be placed indoors, on a slab outdoors aboveground, or underground in an outdoor pit. The plumbing contractor is usually responsible for a pit, if required, a slab, telephone outlet, and electrical outlet adjacent to the meter. The utility company almost always supplies the meter. The utility company usually runs the service on the consumer’s site up to the meter, terminating with a shutoff valve.

pressure reGulatinG valvesA pressure regulator is a device for reducing a variable high inlet pressure to a constant lower outlet pressure. The line regulator is used to reduce supply line pressure from generally 25–50 psig (170–345 kPa) to an intermediate pressure of about 3–5 psig (21–35 kPa). If used, it is usually placed outside before the meter and selected by the utility company. If installed inside the building, a relief vent will be necessary. An intermediate regulator is used to

Table 2 Physical and Combustion Properties of Commonly Available Fuel Gases

No. Gas

Heating valueHeat release, Btu Specific

gravityDensity, lb per ft3

Specific volume

ft3/lbBtu/ft3 Btu/lb

Gross Net Gross Net Per ft3 air Per lb air1 Acetylene 1,498 1,447 21,569 20,837 125.8 1677 0.91 0.07 14.42 Blast furnace gas 92 92 1,178 1,178 135.3 1804 1.02 0.078 12.83 Butane 3,225 2,977 21,640 19,976 105.8 1411 1.95 0.149 6.714 Butylene (hutene) 3,077 2,876 20,780 19,420 107.6 1435 1.94 0.148 6.745 Carbon monoxide 323 323 4,368 4,368 135.7 1809 0.97 0.074 13.56 Carburetted water gas 550 508 11,440 10,566 119.6 1595 0.63 0.048 20.87 Coke oven gas 574 514 17,048 15,266 115.0 1533 0.44 0.034 29.78 Digester (sewage) gas 690 621 11,316 10,184 107.6 1407 0.80 0.062 16.39 Ethane 1,783 1,630 22,198 20,295 106.9 1425 1.05 0.080 12.5

10 Hydrogen 325 275 61,084 51,628 136.6 1821 0.07 0.0054 186.911 Methane 1,011 910 23,811 21,433 106.1 1415 0.55 0.042 23.812 Natural (Birmingham, AL) 1,002 904 21,844 19,707 106.5 1420 0.60 0.046 21.813 Natural (Pittsburgh, PA) 1,129 1,021 24,161 21,849 106.7 1423 0.61 0.047 21.414 Natural (Los Angeles, CA) 1,073 971 20,065 18,158 106.8 1424 0.70 0.054 18.715 Natural (Kansas City, MO) 974 879 20,259 18,283 106.7 1423 0.63 0.048 20.816 Natural (Groningen, Netherlands) 941 849 19,599 17,678 111.9 1492 0.64 0.048 20.717 Natural (Midlands Grid, U.K.) 1,035 902 22,500 19,609 105.6 1408 0.61. 0.046 21.818 Producer (Wellman-Galusha) 167 156 2,650 2,476 128.5 1713 0.84 0.065 15.419 Propane 2,572 2,365 21,500 19,770 108 1440 1.52 0.116 8.6120 Propylene (Propane) 2,332 2,181 20,990 19,030 108.8 1451 1.45 0.111 9.0221 Sasol (South Africa) 500 443 14,550 13,016 116.3 1551 0.42 0.032 31.322 Water gas (bituminous) 261 239 4,881 4,469 129.9 1732 0.71 0.054 18.7

JANUARY/FEBRUARY 2008 Plumbing Systems & Design 3


further reduce the pressure from 3–5 psig (21–35 kPa) to one that can be used by terminal equipment, which is approximately 7 in. (178 mm) wc. Different types of valves may require a relief vent. An appliance regulator connects the supply to the terminal equipment and may be provided by the equipment manufacturer, usually on gas trains where equipment has one. Types of appliance regula-tors are a zero governer, a backpressure regulator, and a differential regulator.

When regulators are installed inside a building and require a vent, these vents often must be routed to the atmosphere. The vents from individual regulators may not be combined. When bottled gas is used, the tank can have as much as 150 psi (1034.6 kPa) pressure to be reduced to the burner design pressure of 11 in. (279.4 mm) wc. The regulator normally is located at the tank for this pressure reduction.

pressure control valvesAn excess flow valve is a device that shuts off the flow of gas if there is a much larger flow through the pipe or service than designed for. In some parts of the country, particularly in areas where earth-quakes may occur, excessive flow valves are necessary to guard against the possibility of a break during such an event. In other cases, where danger exists for equipment such as large boilers, installation should be considered.

A low pressure cutoff shall be installed between the meter and appliance where the operation of a device, such as a gas compres-sor, appliance, or a boiler, could produce a vacuum or dangerous vacuum condition in the piping system.

appliance control valvesAn appliance shutoff valve shall be installed at all gas appliances prior to any flexible hose used to connect the appliance to the building gas supply.

interlocksAn automatic interlock, connected to the automatic fire extinguish-ing system, is required to shut off the gas supply to all equipment in a kitchen when there is a discharge in the event of a fire. In earth-quake-prone areas, an interlock is required to shut off the supply of gas if the disturbance may rupture the pipe or separate pipe from any equipment.

appliancesAppliances are listed by types and categories that shall be used in the design of vents. These vents shall be sized and located in accor-dance with NFPA 54.

Most manufacturers of gas appliances rate their equipment by the gas consumption values that are used to determine the maxi-mum gas flow rate in the piping. Table 3 shows the approximate gas consumption for some common appliances. To find the flow rate of gas required, use the consumption from the manufacturer and divide by 1,000. If the equipment is a water heater, multiply the figure by the weight of water (8.48 lbs).

The products of combustion from an appliance must be safely exhausted to the outside. This is accomplished with a gas vent system in most cases. Where an appliance has a very low rate of gas consumption (e.g., Bunsen burner or countertop coffee maker) or where an appliance has an exhaust system associated with the appliance (e.g., gas clothes dryer or range) and the room size and ventilation are adequate, a separate gas vent system may not be required. Current practice usually dictates the use of factory-fab-ricated and listed vents for small to medium-size appliances. Large appliances and equipment may require specially designed venting or exhaust systems. It is not the plumbing engineer’s responsibility

to design and specify gas vents. This is done by either the HVAC department or the manufacturer.

Where the ratings of the appliances are not known, they shall comply with the typical demand of appliances by types as indicated in NFPA 54.

allowable Gas pressureThe gas outlet pressure in the piping system downstream of the meter that is supplied by the utility is mostly in the range of 4–14 in. (102–356 mm) wc, with approximately 7 in. (178 mm) wc being a common figure. Good engineering practice limits the pressure losses in the piping to approximately 0.2–0.5 in. (5–12.7 mm) wc depending on the outlet pressure, with 0.3 in. (7.6 mm) wc being the most commonly used number. However, local codes may dic-tate a more stringent pressure drop maximum. The AHJ should be consulted before the system is sized. Most appliances require approximately 3.5 in. (89 mm) wc; however, the designer must be

Table 3 Approximate Gas Demand for Common Appliances a

ApplianceInput, Btu/h (mJ/h)

Commercial kitchen equipmentSmall broiler 30,000 (31.7)Large broiler 60,000 (63.3)Combination broiler and roaster 66,000 (69.6)Coffee maker, 3-burner 18,000 (19)Coffee maker, 4-burner 24,000 (25.3)Deep fat fryer, 45 lb (20.4 kg) of fat 50,000 (52.8)Deep fat fryer, 75 lb (34.1 kg) of fat 75,000 (79.1)Doughnut fryer, 200 lb (90.8 kg) of fat 72,000 (76)2-deck baking and roasting oven 100,000 (105.5)3-deck baking oven 96,000 (101.3)Revolving oven, 4 or 5 trays 210,000 (221.6)Range with hot top and oven 90,000 (95)Range with hot top 45,000 (47.5)Range with fry top and oven 100,000 (105.5)Range with fry top 50,000 (52.8)Coffee urn, single, 5-gal (18.9 L) 28,000 (29.5)Coffee urn, twin, 10-gal. (37.9 L) 56,000 (59.1)Coffee urn, twin, 15-gal (56.8 L) 84,000 (88.6)Stackable convection oven, per section of oven 60,000 (63.3)

Residential equipmentClothes dryer (Type I) 35,000 (36.9)Range 65,000 (68.6)Stove-top burners (each) 40,000 (42.2)Oven 25,000 (26.4)30-gal (113.6-L) water heater 30,000 (31.7)40 to 50-gal (151.4 to 189.3-L) water heater 50,000 (52.8)Log lighter 25,000 (26.4)Barbecue 50,000 (52.8)

Miscellaneous equipmentCommercial log lighter 50,000 (52.8)Bunsen burner 5,000 (5.3)Gas engine, per horsepower (745.7 W) 10,000 (10.6)Steam boiler, per horsepower (745.7 W) 50,000 (52.8)

Commercial clothes dryer (Type 2)See manufacturer’s

data.a The values given in this table should be used only when the manufacturer’s data are not available.


CONTINUING EDUCATION: Fuel Gas Piping Systems


aware that large appliances, such as boilers, may require higher gas pressures to operate properly. Where appliances require higher pressures or where long distribution lines are involved, it may be necessary to use higher pressures at the meter outlet to satisfy the appliance requirements or provide for greater pressure losses in the piping system. If greater pressure at the meter outlet can be attained, a greater pressure drop can be allowed in the piping system. If the greater pressure drop design can be used, a more eco-nomical piping system is possible.

laboratory usaGeNG is the primary gas used in laboratories at lab benches for Bunsen burners. Where NG is not available, propane gas is used, but this generally requires the manufacturer to be advised due to the Bunsen burner requiring a smaller orifice. Typical Bunsen burners consume either 5 cfh (0.15 m3/h) (small burners) or 10 cfh (0.30 m3/h) (large burners).The maximum pressure at the burner should not exceed 14 in. (355.6 mm) wc. 10 cfh (0.30 m3/h) is more commonly used.

Some local codes require laboratory gas systems, especially those in schools or universities, to be supplied with emergency gas shutoff valves on the supply to each laboratory. The valve normally should be closed and opened only when the gas is being used. It should be located inside the laboratory and used in conjunction with shut-off valves at the benches or equipment, which may be required by other codes. The designer should ensure locations meet local code requirements.

The following diversities, found in Table 4, shall be applied where flow will be from Bunsen burners:

Branch piping that serves one or two laboratory classrooms should be sized for 100% usage regardless of the number of outlets. Use factors should be modified to suit special conditions and must be used with judgment after consultation with the owner and /or user.

Gas reGulator relief ventsGuidelines for the use of relief vents from pressure regulators, also referred to as gas-train vents, can be found in the latest editions of NFPA 54 and FM Global Loss Prevention Data Sheet 6-4: Oil- and Gas-Fired Single-Burner Boilers, as well as in other publications of industry standards, such as those issued by Industrial Risk Insurers and the American Gas Association.

It should be noted that when the pressure regulators discharge, large amounts of fuel gas may be released. It is not uncommon for a local fire department to be summoned to investigate an odor of gas caused by a gas-train vent discharge. Every attempt should be made to locate the terminal point of the vents above the line of the

roof and away from doors, windows, and fresh-air intakes. It also should be located on a side of the building that is not protected from the wind. Refer to NFPA 54 and local codes for vent locations.

altitude deratinG factorNG has a reduced density at a higher altitude that must be allowed for when the project location is more than 2,000 feet above sea level. This altitude correction factor shall be multiplied by the gas input at sea level to determine the correct input at full load capacity. Refer to Figure 1 to determining the derating factor for NG.

pipinG system materialsThe following piping materials are the most often used for both NG and propane.

Pipe Steel (galvanized, plastic-wrapped, or black), brass, and copper. Black steel is the most commonly used pipe. Cast-iron pipe shall not be used.

Tubing Semi-rigid copper type K or L.Plastic pipe and tubing (polyethylene) Plastic pipe may be used

outside and underground only.

flexible hose

corruGated stainless steel tubinGIndoor Indoor gas hose connectors may be used with laboratory or shop and other equipment that requires mobility during operation or installation, if listed for this application. A shutoff valve must be installed where the connector is attached to the building piping. The connector must be of minimum length but shall not exceed 6 ft (1.8 m). The connector must not be concealed and must not extend from one room to another nor pass through wall partitions, ceil-ings, or floors.

Outdoor Outdoor gas hose connectors may be used to connect portable outdoor gas-fired appliances, if listed for this application. A shutoff valve or a listed quick-disconnect device must be installed where the connector is attached to the supply piping and in such a manner as to prevent the accumulation of water or foreign matter.

Figure 1 Altitude Correction Factor

The Altitude Correction Factor (ACF) should be multiplied by the gas input at sea level to determine the corrected input. Sizing of the equipment is then performed utilizing this corrected input multiplied by the full load efficency.

Table 4 Laboratory Diversity Factors

Number of Outlets

Laboratory Diversity

Factor Flow cfh

(m3/h) 1–8 100 9 (0.26)

9–16 90 15 (0.43) 17–29 80 24 (0.68) 30–79 60 48 (1.36)

80–162 50 82 (2.32) 163–325 45 107 (3.03) 326–742 40 131 (3.71)

743–1,570 30 260 (7.36) 1,571–2,900 25 472 (13.37) 2,901 and up 20 726 (20.56)



This connection must be made only in the outdoor area where the appliance is to be used.

Fittings and joints for low-pressure piping, 3 psi (21 kPa) or less Steel pipe may be threaded, flanged, or welded. Cast or mal-leable iron threaded fittings are the most commonly used. Tubing may be soldered or brazed using wrought copper or copper alloy fittings and no flux. Brazing alloy must not contain phosphorous.

Fittings and joints for high pressure piping greater than 3 psi (21 kPa) Steel pipe and fittings 4 in. (100 mm) and larger shall be welded.

Tubing joints Tubing usually is needed for the flexible connec-tions to equipment. For pressures normally encountered in the uti-lization of NG and LPG, the most often used joints are screwed.

desiGn considerationsThe fact that LPG vapors are heavier than air has a practical bearing on several items. For one thing, LPG systems are located in such a manner that the hazard of escaping gas is kept at a minimum.

Since the heavier-than-air gas tends to settle in low places, the vent termination of relief valves must be located at a safe distance from openings into buildings that are below the level of such valves. With many gas systems, both the gas pressure regulator and the fuel containers are installed adjacent to the building they serve. This distance must be a least 3 ft (0.91 m) measured horizontally. How-ever, the required clearances vary according to the tank size and the adjacent activities. The designer should refer to the local code and NFPA 54 for these clearances.

When LPG piping is installed in crawl spaces or in pipe tunnels, the engineer may consider a sniffer system, which automatically shuts down the gas supply, sounds an alarm, and activates an exhaust system to purge the escaping gas from the area upon detec-tion of gas in the space due to a breach in the piping system.

GAS BOOSTERSA gas booster is a pump that increases the pressure of gas. It is used when there is insufficient pressure available from the gas utility or LPG storage device to supply the necessary pressure to the equip-ment at hand. It is important to note that the gas service must be capable of the volumetric flow rate required at the boosted level. A booster cannot overcome an inadequate volumetric supply.

Gas boosters for natural or liquefied petroleum gas Boosters for natural or utility-supplied gas are hermetically sealed and are equipped to deliver a volumetric flow rate (user defined but within the booster’s rated capacity) to an elevated pressure beyond the supply pressure. The outlet pressure usually remains at a constant differential above the supply pressure within a reasonable range. The discharge pressure is the sum of the incoming gas pressure and the booster-added pressure at the chosen flow rate. The incoming gas pressure usually has an upper safety limit as stipulated by the hermetic gas booster manufacturer. Therefore, in the engineering literature from the manufacturer, the engineer may find cautions or warnings about the upper limits of incoming pressure, usually about 5 psi (34.5 kPa).

materials of constructionHousing and rotor Boosters used for fuel gas must be Underwrit-ers Laboratories (UL) listed for the specific duty intended and shall be hermetically sealed. Casings on standard boosters usually are constructed of carbon steel, depending on the equipment supplier. Booster casings are also available in stainless steel and aluminum. Inlet and outlet connections are threaded or flanged, depending on the pipe size connection and the manufacturer selected, and the casings are constructed leak tight. Drive impellers are contained within the casing and always manufactured of a spark-resistant material such as aluminum.

Discharge-type check valves are furnished on the booster inlet and on the booster bypass. It is important that these valves are listed and approved for use on the gas service at hand. The fan, control panel, valves, piping, and interelectrical connections can be specified as a skid-mounted package at the discretion of the designer. This allows for UL listing of the entire package rather than of individual components.

Electrical components Motor housings for gas booster systems are designed for explosion-proof (XP) construction and are rated per National Electrical Manufacturers Association (NEMA) Class 1, Division 1, Group D classification with thermal overload protec-tion. A factory UL-listed junction box with a protected, sealed inlet is necessary for wiring connections.

Figure 2 Variations of a Basic Simplex Booster System: (A) Standby Generator Application with Accumulator Tank Having a Limitation on Maximum Pressure




Other electrical ancillary equipment Boosters are equipped with low pressure switches that monitor the incoming gas pressure. The switch is designed to shut down the booster should the utility-supplied pressure fall below a preset limit. The set point is usually about 3 in. (76 mm) wc, but the designer should verify the limit with the local gas provider. The switch must be UL listed for use with the gas service at hand. When the switch opens, it de-energizes the motor control circuit and simultaneously outputs both audible and visual signals, which require manual resetting. The booster can be equipped with an optional high/low gas pressure switch. This fea-ture equips the booster to run only when adequate supply pressure

is available. The switch shuts the booster down at the maximum discharge setpoint pressure at the output line pressure.

Minimum gas flow Gas boosters normally require a minimum gas flow that serves as an internal cooling medium. For example, a booster sized at a flow rate of 10,000 cfh (283.2 m3/h) has an inher-ent minimum turndown based on the minimum flow required to cool the unit. This rate, in the example, may be 2,000 cfh (566.3 m3/h) (see Figure 2). Should the unit be required to run below this turndown rate, additional supplemental cooling systems must be incorporated into the booster design. The heat exchangers normally rated for this use are water cooled.

(C)Figure 2 Variations of a Basic Simplex Booster System: (B) Dual Booster System for Critical Systems Like Those in Hospitals, (C) Heat Exchanger Loop

Example—Required for High Flow Range with Low Minimum Flow.

(B)



Intrinsic safety Electrical connections are made through a sealed, explosion-proof conduit to the XP junction box on the booster unit. Control panels are rated NEMA 4 for outdoor use and NEMA 12 for indoor use unless the booster system is to be located in a hazardous area, which may have additional requirements. The panel, as an assembly, must display a UL label specific for its intended use.

Gas laws for boostersPressure/volume relationships The gas laws apply to the relation-ship of the incoming gas supply and the boosted service. The stan-dard law for compressed gas relationships is as follows:

Equation 1

PV = RTwhere P = Pressure, psi or in. wc (kPa or mm wc) V = Volume, cfh (m3/h) R = Constant for the gas/air mixture used T = Temperature, °F (°C)

Usually the temperature of the gas remains relatively constant and can be ignored in the relationship. Therefore, the pressure times the volume is proportional to a constant R. Further, the pres-sure/volume ratios before and after the booster are proportional, that is:

Equation 2

P1V1 = P2V2

where P1 = Pressure at a point prior to the booster P2 = Pressure at a point after the booster

For almost every case, the volumetric rating of gas-fired equip-ment is in Btu/h, which can readily be converted to cfh. In the booster application, sizing criteria should be approached from a standard cfh (scfh) not an actual cfh (acfh) rating.

Gas temperatures and density As stated, the temperature of the gas is usually constant. However, in the event that the gas is to be heated or cooled, the previously mentioned gas laws are affected by temperature. Gas density changes affect the constant but usu-ally do not affect the relationship since the same mixture is boosted across the fan.

High-rise building issues Consideration must be given to the rise effect in available gas pressure as gas rises in the piping through a high-rise building. Therefore, if the gas system supplies a kitchen on the first level and a boiler in the penthouse of a 50-story build-ing, it may be necessary to boost the supply to the kitchen but not to the boiler. The gas rises to the penthouse through the piping system because of the density differential; its rising is dependent on this stack effect, which is directly related to the piping system layout.

Design considerations Although a gas booster is a basic mechanical piece of equipment, there are significant design con-siderations that should be taken into account when applying it:1. Indoor vs. outdoor location. This may be driven by local code

or the end user. An indoor location involves a lower initial cost and lower costs for long-term maintenance. Outdoor locations are inherently safer.

2. Access. The location should be accessible for installation, inspection, and maintenance. The unit should not be so accessible as to create a security issue. Keep the equipment out of traffic patterns and protect it from heavy equipment.

3. Minimum and maximum flow rates. Boosters usually have a minimum flow rate that must be maintained so that the

booster’s motor is kept cool. When specifying a booster, always indicate the minimum flow required in addition to other design parameters. Cooling devices and bypass loops may be required if the application requires a turndown in flow (lowest flow expected) that is higher than the booster’s mini-mum flow.

4. Controls and interlocking. Determine how the application should be controlled and what demands the application will put on the system. The control philosophy, method of electri-cally interlocking the system to the gas-fired equipment, and physical hardware will vary based on the application.

For some specific examples, see the schematics in Figure 2, which shows variations of a basic simplex booster system for an emer-gency generator. In Figure 2(A), the regulator controls maximum delivered pressure, and a combination high/low pressure switch on the tank cycles the booster to ensure emergency startup pressure within a design deadband for the generator. Oversized piping, in this case, can be substituted for the tank itself. Provide adequate volume so that the generator can fire and deliver standby power back to the booster system to continue operation during main power interrupt. In Figure 2(B), a dual booster system, the booster is controlled in a lead/lag control scenario. Should one booster fail, the second is started automatically. Unit operation is rotated automatically via the control panel to share the duty and to keep both units in operating order. The booster with a heat exchanger loop shown in Figure 2(C) has a potential of up to 15 psi (103.4 kPa) and down to 28 in. (711.2 mm) wc supply pressure. The system automatically diverts gas around the booster if there is sufficient supply pressure. While these illustrations obviously do not cover all the potential applications, they are provided to give the system designer some guidance.

Sizing a gas booster A gas booster’s main purpose is to elevate the pressure of a volume of gas to overcome a supply pressure defi-ciency. When sizing a booster, an engineer needs to understand the following terms and issues:

Maximum design flow (Qmax) The sum of all gas loads at the maximum capacity rating (MCR) for all equipment downstream of the booster that could possibly be required to operate simultane-ously.

Minimum design flow (Qmin) The minimum volumetric flow that could exist while the booster is operating. This flow is not always associated with the smallest Btu/h-rated piece of equipment. For example, when evaluating a 75,000,000 Btu/h (22 MW) boiler with a 10:1 turndown ratio in comparison to a 1.0 Btu/h (0.3 W) hot water heater that is on/off in operation, the larger Btu/h (W)-rated boiler has the smaller flow of 0.75 Btu/h (0.2 W) at its minimum firing rate.

Turndown (TD) ratio The ratio of the MCR input to the equip-ment’s minimum, or low-fire, input. For example, a 100 Btu/h (29.3 W) burner that can fire at a minimum rate of 20 Btu/h (5.9 W) has a TD ratio of 5:1.

Pressure droop and peak consumption Pressure droop is the inability of a supply system to maintain a steady or consistent inlet pressure as an increase in volumetric flow is demanded. Often, in areas where boosters are applied, the supply pressure in off-peak months when gas is not in such demand can be sufficient to run a system. As the local demand for gas increases, the supply system no longer can provide the gas efficiently and the pressure falls off or droops. It is the booster’s function to overcome the droop (or exces-sive pressure drop) of the supply system during such times.

Flow rate relationships Do your flows for separate pieces of equipment relate to each other? In other words, do the three boil-




ers always operate in unison while another process machine always operates off peak and alone? Relationships among the equipment can significantly affect both maximum and minimum flow rates.

Test block A factor of safety added to design criteria. Typically, a minimum of 5% added volume and 10% added static pressure should be applied to the design criteria. When specifying the equip-ment, ensure that you note both the design and test block condi-tions. This makes other people working on the system aware and ensures that safety factors are not applied to criteria that already include safety factors.

Minimum inlet pressure (PI-min) What is the minimum supply pressure in in. (mm) wc gauge? This must be evaluated during peak flow demands both for the equipment and for the local area. Always evaluate during flow, not static, conditions. It is also important to know how high the inlet pressure is expected to rise during off-peak periods. A booster is typically rated to about 5 psi (34.5 kPa). It may be possible to exceed this rating during off-peak demand periods; therefore, a bypass system or other means of protection is required. Often this pressure can be specified by the local gas company as the minimum guaranteed gas pressure from their supply system. Also, the maximum inlet pressure (PI-max) must be determined.

Maximum outlet pressure (PO-max) List all maximum and required supply pressures for the various pieces of equipment being supplied gas from the booster. Determine the differential between the highest expected gas pressure supply to the booster (e.g., 8 in. [203.2 mm] wc) and the lowest maximum supply pressure rating to a piece of equipment (e.g., 18 in. [457.2 mm] wc). The booster’s pressure gain should not exceed this differential (for the above example, 18 – 8 = 10 in. [457.2 – 203.2 = 254 mm] wc) unless other means of protecting the downstream equipment are provided.

Outlet pressure protection There are several ways to protect equipment downstream of a booster should it be necessary due to potential over-pressurization during off-peak periods. If all the equipment being serviced operates at nominally the same pressure, install a regulator on the inlet or outlet of the booster to maintain a controlled maximum outlet pressure. If the equipment being ser-viced operates at various inlet pressures, it may be best to supply a regulator for each piece of equipment. Most often, packaged equip-ment is supplied with its own regulator. If this is the case, review the equipment regulator’s maximum inlet pressure.

To perform an evaluation of system requirements, do the following:1. Establish design Qmin and Qmax per the previously discussed

definitions while evaluating TD requirements.2. Establish PI-min and PI-max per the previously discussed defini-

tions.3. Define maximum inlet pressure requirements to equipment

(PI-eq).

4. Define piping pressure losses (PPL) from the gas booster loca-tion to each piece of equipment.

5. Design flow rate (QD) = Qmin to Qmax, cfh (m3/h).6. Design pressure boost (DP) = PI-eq + PPL – PI-min.7. Test block flow (QTB) = (1.05 × Qmin) to (1.05 × Qmax).8. Test block pressure boost: 1.10 × DP = PI-eq + PPL – PI-min.

wherePPL = Pressure losses, psi (kPa)

interior nG pipe sizinGTo accurately size all elements of the piping system, calculate or obtain the following information:1. The information needed by both the utility company and the

engineer.2. The gas pressure available after the meter assembly.

3. The allowable friction loss through the piping system.4. A piping layout that shows all the connected equipment,

allowing determination of the measured length of piping to the furthest connection. This, in turn, gives the equivalent length of piping.

5. The maximum probable demand.6. A pipe sizing method acceptable to the AHJ or local code.

The information needed by both the utility company and the engineer The following are intended to be complete lists of items. Not all items will be necessary for all projects.

The following criteria and information shall be obtained in writ-ing from the public utility company and given to the engineer:1. BTU content of the gas provided.2. Minimum pressure of the gas at the outlet of the meter.3. Extent of the installation work done by the utility company

and the point of connection to the meter by the facility con-struction contractor.

4. The location of the utility supply main and the proposed run of pipe on the site by the utility company. This shall be in the form of a marked-up plan or description of the work. Include the expected date of installation if no gas is available.

5. Acceptable location of the meter and /or regulator assembly or a request to locate the meter at a particular location.

6. Any work required by the owner to allow the meter assembly to be installed (such as a meter pit or slab on grade).

7. Types of gas service available and the cost of each.

For the utility company to provide this data, the fol lowing infor-mation must be provided to them:1. The total connected load. The utility will use its own diversity

factor to calculate the size of the service line. For the design of the project’s interior piping, the design engineer will select the diversity factor involved.

2. Minimum pressure requirements for the most demanding device.

3. Site plan indicating the location of the proposed building on the site and the specific area of the building where the pro-posed NG service will enter the building.

4. Preferred location of the meter/regulator assembly5. Expected date of the start of construction.6. Different requirements for pressure.7. Two site plans, one to be marked up and returned to the engi-

neer.8. If any equipment has pilot lights.9. The hours of operation for the different types of equipment.10. Future equipment and capacities, if any, known at this time.

The pressure available after the meter shall be established in writing from the utility at the start of the project. If boilers or other major equipment is being used, the pressure requirements and the flow rate for that equipment must be provided to the utility.

The allowable friction loss through the entire piping system shall be established by the engineer. This value depends on the pressure provided by the utility company. The most often selected value under average conditions is 0.3 in. (7.6 mm) wc, with a range of 0.2–0.5 in. (5–13 mm) wc. The residential appliances (range and dryer) require a pressure of 3.5 in. (89 mm) wc. If the pressure from the utility company is around 7 in. (178 mm) wc, a higher friction loss allowance could be used for economy in pipe sizing. If the pressure from the utility company is 4 in. (102 mm) wc, a 0.2 in. (5 mm) wc is recommended.

A piping layout and the equivalent length of piping A piping layout is necessary to show the run of the whole piping system and



all the connected appliances and equipment. The equivalent length of piping is calculated by measuring the actual length of proposed piping from the meter to the furthest connection and then adding 50% of the measured length to find the equivalent length. If a very accurate determination of the equivalent length is necessary, it will be necessary to count the fittings and valves and then add those to the measured length. Refer to Table 5 for the equivalent amount of pipe to be added for various valves and fittings.

It is common practice not to use the vertical length in either calculation because NG is lighter than air. It expands at the rate of 1 in. (25.4 mm) wc for each 15 ft of elevation as the gas rises. The increase in pressure due to the height will offset any friction loss in the piping.

The maximum probable demand is calculated by the engineer with input from the owner if necessary. The primary usage of gas is for cooking and clothes drying at residences, for Bunsen burners or heating (boilers) in laboratories, or cooling equipment in indus-trial projects. For residential usage, Figure 3 for large residences

and Figure 4 for smaller projects give a direct reading of the usage in cfh (m3/hr). These direct reading tables give flow rate usage by using the number of apartments. Figure 5 is a riser diagram of mul-tiple dwellings that gives the size of gas risers used for cooking and drying for both single and back-to-back installations. For laborato-ries, use Table 5 for the diversity factor. For schools, use no diversity factor for individual classrooms. Use no diversity factor for groups of classrooms if information of proposed usage is not conclusive or available from the owner. For industrial usage, a diversity factor generally is not used because of the possibility that all equipment may be in use at one time.

For a listing of input requirements for common appliances, refer to Table 3.

nG pipe sizinG methodsA number of formulas can be used to calculate the capacity of NG piping based on such variables as delivery pressure, pressure drop through the piping system, pipe size, pipe material, and length of piping. These formulas are referenced in numerous current model

Table 5 Equivalent Lengths for Various Valve and Fitting Sizes

Pipe Size, in. (mm)

Fitting ¾ (19.1) 1 (25.4) 1½ (38.1) 2 (50.8) 2½ (63.5) 3 (76.2) 4 (101.6) 5 (127) 6 (152.4) 8 (203.2)

Equivalent Lengths, ft (m)

90° elbow 1.00 (0.3) 2.00 (0.61) 2.50 (0.76) 3.00 (0.91) 4.00 (1.22) 5.50 (1.68) 6.50 (1.98) 9.00 (2.74) 12.0 (3.66) 15.0 (4.57)

Tee (run) 0.50 (0.15) 0.75 (0.23) 1.00 (0.3) 1.50 (0.46) 2.00 (0.61) 3.00 (0.91) 3.50 (1.07) 4.50 (1.37) 6.00 (1.83) 7.00 (2.13)

Tee (branch) 2.50 (0.76) 3.50 (1.07) 4.50 (1.37) 5.00 (1.52) 6.00 (1.83) 11.0 (3.35) 13.0 (3.96) 18.0 (5.49) 24.0 (7.32) 30.0 (9.14)

Gas cock (approx.) 4.00 (1.22) 5.00 (1.52) 7.50 (2.29) 9.00 (2.74) 12.0 (3.66) 17.0 (5.18) 20.0 (6.1) 28.0 (8.53) 37.0 (11.28) 46.0 (14.02)Note: The pressure drop through valves should be taken from manufacturers’ published data rather than using the equivalent lengths, since the various patterns of gas cocks can vary greatly.

Figure 3 Gas Demand for Multiple-unit Dwellings with More Than 50 Apartments




codes as well as in NFPA 54. The most commonly referenced for-mula for gas pressures under 1½ psi (10.3 kPa) is the Spitzglass formula. The other commonly referenced equation for pressures of 1½ psi (10.3 kPa) and more is the Weymouth formula. Using these formulas for sizing is a very cumbersome task, so they are rarely, if ever, used. However, they were used as a basis for the sizing tables that are included in this chapter and reproduced with permission from the NFPA. These tables are regarded as the most conserva-tive method for sizing NG pipe. Proprietary tables and calculators are available from various organizations and are considered more accurate than those shown here.

The tables are based on Schedule 40 steel pipe, cfh of gas, and a specific gravity of 0.60. The initial pressures are different, and the friction loss allowable is indicated. The following tables are pro-vided:Table 6 pressure less than 2 psi (14 kPa), loss of 0.3 in. (7.5 mm)

wcTable 7 pressure less than 2 psi (14 kPa), loss of 0.5 in. (12.5 mm)

wcTable 8 pressure of 5 psi (35 kPa), loss of 10 percentTable 9 pressure 10 psi (70 kPa), loss of 10 percentTable 10 pressure 20 psi (140 kPa), loss of 10 percentTable 11 pressure 50 psi (350 kPa), loss of 10 percentNote 1 cfh gas = 0.3 m3/hr

To determine the size of each section of pipe in a gas supply system using the gas pipe sizing tables, the following method should be used:1. Measure the length of the pipe from the gas meter location

to the most remote outlet on the system. Add a fitting allow-ance of 50% of the measured length. This now gives you the equivalent length of pipe. For natural gas, the vertical portion

of piping is not considered due to the pressure gained as the gas rises. This very closely approximates the friction loss in the piping.

2. Select the column showing the distance that is equal to or more than the equivalent length just calculated.

3. Use the vertical column to locate all gas demand figures for this particular system. This is the only column to use. Start-ing at the most remote outlet, find in the vertical column the calculated gas demand for that design point. If the exact figure is not shown, choose the figure closest to or more than the calculated demand.

4. Opposite this demand figure selected, in the column at the left, find the correct size of pipe.

5. Proceed for each design point and each section of pipe. For each section of pipe, determine the total gas demand supplied by that section.

If the gas used for the system has a different specific gravity than natural gas, obtain that figure from Table 12 and use this as a multi-plier for the specific gas selected.

Figure 5 Gas Riser Pipe Sizing for Multiple Dwellings

Figure 4 Gas Demand for Multiple-unit Dwellings with Less than 50 Apartments



To convert gas pressure to various designations, refer to Table 13.

LIQUEFIED PETROLEUM GASLiquefied petroleum gas (LPG) is a refined NG developed mainly for use beyond the utilities’ gas mains, but it has proven to be com-petitive in areas not covered by mains in rural areas. It is chiefly a blend of propane and butane with traces of other hydrocarbons remaining from the various production methods. The exact blend is controlled by the LPG distributor to match the climatic condi-tions of the area served. For this reason, the engineer must confirm the heat value of the supplied gas. Unlike natural gas, 100 percent propane has a specific gravity of 1.53 and a rating of 2,500 Btu/cf (93 MJ/cm3).

Easy storage for relatively large quantities of energy has led to widespread acceptance and usage of LPG in all areas previously served by utilities providing NG to users, including automotive purposes. In addition, a principal use is for the heating of industrial projects. It does not take the place of NG but provides an alternative energy source when the owners want to use a low, interruptible rate for heating purposes. When used for this purpose, experience has shown that the mixing with air should produce a gas with the heat-ing value of 1,500 Btu/cf (a specific gravity of 1.30) for ease of burn-ing and ignition. Use Table 12 for the factor to be used for sizing.

storaGeLPG storage tanks can be provided by the vendor or the customer and are subject to the regulations of the U.S. Department of Trans-portation (DOT) and the local authority, as well as NFPA standards,

Table 6 Pressure less than 2 psi (14 kPa), loss of 0.3 in. (7.5 mm) wc

Pipe Size (in.)Nominal 1⁄2 3⁄4 1 11⁄4 11⁄2 2 21⁄2 3 4 5 6 8 10 12Actual ID 0.622 0.824 1.049 1.380 1.610 2.067 2.469 3.068 4.026 5.047 6.065 7.981 10.020 11.938

Length (ft) Capacity in Cubic Feet of Gas per Hour10 131 273 514 1,060 1,580 3,050 4,860 8,580 17,500 31,700 51,300 105,000 191,000 303,00020 90 188 353 726 1,090 2,090 3,340 5,900 12,000 21,800 35,300 72,400 132,000 208,00030 72 151 284 583 873 1,680 2,680 4,740 9,660 17,500 28,300 58,200 106,000 167,00040 62 129 243 499 747 1,440 2,290 4,050 8,270 15,000 24,200 49,800 90,400 143,00050 55 114 215 442 662 1,280 2,030 3,590 7,330 13,300 21,500 44,100 80,100 127,00060 50 104 195 400 600 1,160 1,840 3,260 6,640 12,000 19,500 40,000 72,600 115,00070 46 95 179 368 552 1,060 1,690 3,000 6,110 11,100 17,900 36,800 66,800 106,00080 42 89 167 343 514 989 1,580 2,790 5,680 10,300 16,700 34,200 62,100 98,40090 40 83 157 322 482 928 1,480 2,610 5,330 9,650 15,600 32,100 58,300 92,300

100 38 79 148 304 455 877 1,400 2,470 5,040 9,110 14,800 30,300 55,100 87,200125 33 70 131 269 403 777 1,240 2,190 4,460 8,080 13,100 26,900 48,800 77,300150 30 63 119 244 366 704 1,120 1,980 4,050 7,320 11,900 24,300 44,200 70,000175 28 58 109 224 336 648 1,030 1,820 3,720 6,730 10,900 22,400 40,700 64,400200 26 54 102 209 313 602 960 1,700 3,460 6,260 10,100 20,800 37,900 59,900250 23 48 90 185 277 534 851 1,500 3,070 5,550 8,990 18,500 33,500 53,100300 21 43 82 168 251 484 771 1,360 2,780 5,030 8,150 16,700 30,400 48,100350 19 40 75 154 231 445 709 1,250 2,560 4,630 7,490 15,400 28,000 44,300400 18 37 70 143 215 414 660 1,170 2,380 4,310 6,970 14,300 26,000 41,200450 17 35 66 135 202 389 619 1,090 2,230 4,040 6,540 13,400 24,400 38,600500 16 33 62 127 191 367 585 1,030 2,110 3,820 6,180 12,700 23,100 36,500550 15 31 59 121 181 349 556 982 2,000 3,620 5,870 12,100 21,900 34,700600 14 30 56 115 173 333 530 937 1,910 3,460 5,600 11,500 20,900 33,100650 14 29 54 110 165 318 508 897 1,830 3,310 5,360 11,000 20,000 31,700700 13 27 52 106 159 306 488 862 1,760 3,180 5,150 10,600 19,200 30,400750 13 26 50 102 153 295 470 830 1,690 3,060 4,960 10,200 18,500 29,300800 12 26 48 99 148 285 454 802 1,640 2,960 4,790 9,840 17,900 28,300850 12 25 46 95 143 275 439 776 1,580 2,860 4,640 9,530 17,300 27,400900 11 24 45 93 139 267 426 752 1,530 2,780 4,500 9,240 16,800 26,600950 11 23 44 90 135 259 413 731 1,490 2,700 4,370 8,970 16,300 25,800

1,000 11 23 43 87 131 252 402 711 1,450 2,620 4,250 8,720 15,800 25,1001,100 10 21 40 83 124 240 382 675 1,380 2,490 4,030 8,290 15,100 23,8001,200 NA 20 39 79 119 229 364 644 1,310 2,380 3,850 7,910 14,400 22,7001,300 NA 20 37 76 114 219 349 617 1,260 2,280 3,680 7,570 13,700 21,8001,400 NA 19 35 73 109 210 335 592 1,210 2,190 3,540 7,270 13,200 20,9001,500 NA 18 34 70 105 203 323 571 1,160 2,110 3,410 7,010 12,700 20,1001,600 NA 18 33 68 102 196 312 551 1,120 2,030 3,290 6,770 12,300 19,5001,700 NA 17 32 66 98 189 302 533 1,090 1,970 3,190 6,550 11,900 18,8001,800 NA 16 31 64 95 184 293 517 1,050 1,910 3,090 6,350 11,500 18,3001,900 NA 16 30 62 93 178 284 502 1,020 1,850 3,000 6,170 11,200 17,7002,000 NA 16 29 60 90 173 276 488 1,000 1,800 2,920 6,000 10,900 17,200




so the plumbing designer has little opportunity to design storage tanks and piping, per se. Normally, the designer starts at the storage supply outlet, and the piping system is generally in a low pressure range of 20 psig to 11 in wc.

LPG SIZINGThe pressure of LPG is set by the supplier or the engineer. If the piping is to be run on the site, the pressure would be set higher for economy of pipe sizing, and a regulator would be provided to lower the pressure to a value that would be compatible with equipment served. A lower pressure would be used within a building.

Propane gas shall be sized in accordance with. Tables 14 and 15 that have been developed by the NFPA. Table 14 is based on an outlet pressure of 11 in. wc.(280 mm) that would be suitable for interior piping. Table 15 is based on a higher outlet pressure more

suitable for site mains. The engineer shall obtain or request the pressure provided by the supplier and decide upon the pressure drop in the piping system that would be appropriate. The AHJ shall be consulted regarding acceptance of any pressure selected.

STORAGE TANKSSmall tanks (for example, those for residential cooking and heat-ing) are allowed to be located in close proximity to buildings. Large tanks (e.g., for industrial or multiple building use), however, have strict requirements governing their locations in relation to build-ings, public use areas, and property lines. If large leaks occur, the heavier-than-air gas will hug the ground and form a fog. The poten-tial for a hazardous condition could exist. Proper safety precautions and equipment, as well as good judgment, must be utilized when

Table 7 pressure less than 2 psi (14 kPa), loss of 0.5 in. (12.5 mm) wc

Pipe Size (in.)Nominal 1⁄2 3⁄4 1 11⁄4 11⁄2 2 21⁄2 3 4 5 6 8 10 12Actual ID 0.622 0.824 1.049 1.380 1.610 2.067 2.469 3.068 4.026 5.047 6.065 7.981 10.020 11.938

Length (ft) Capacity in Cubic Feet of Gas per Hour10 172 360 678 1,390 2,090 4,020 6,400 11,300 23,100 41,800 67,600 139,000 252,000 399,00020 118 247 466 957 1,430 2,760 4,400 7,780 15,900 28,700 46,500 95,500 173,000 275,00030 95 199 374 768 1150 2,220 3,530 6,250 12,700 23,000 37,300 76,700 139,000 220,00040 81 170 320 657 985 1,900 3,020 5,350 10,900 19,700 31,900 65,600 119,000 189,00050 72 151 284 583 873 1,680 2,680 4,740 9,660 17,500 28,300 58,200 106,000 167,00060 65 137 257 528 791 1,520 2,430 4,290 8,760 15,800 25,600 52,700 95,700 152,00070 60 126 237 486 728 1,400 2,230 3,950 8,050 14,600 23,600 48,500 88,100 13,90080 56 117 220 452 677 1300 2,080 3,670 7,490 13,600 22,000 45,100 81,900 130,00090 52 110 207 424 635 1220 1,950 3,450 7,030 12,700 20,600 42,300 76,900 122,000100 50 104 195 400 600 1160 1,840 3,260 6,640 12,000 19,500 40,000 72,600 115,000125 44 92 173 355 532 1020 1,630 2,890 5,890 10,600 17,200 35,400 64,300 102,000150 40 83 157 322 482 928 1,480 2,610 5,330 9,650 15,600 32,100 58,300 92,300175 37 77 144 296 443 854 1,360 2,410 4,910 8,880 14,400 29,500 53,600 84,900200 34 71 134 275 412 794 1270 2,240 4,560 8,260 13,400 27,500 49,900 79,000250 30 63 119 244 366 704 1120 1,980 4,050 7,320 11,900 24,300 44,200 70,000300 27 57 108 221 331 638 1020 1,800 3,670 6,630 10,700 22,100 40,100 63,400350 25 53 99 203 305 587 935 1,650 3,370 6,100 9,880 20,300 36,900 58,400400 23 49 92 189 283 546 870 1,540 3,140 5,680 9,190 18,900 34,300 54,300450 22 46 83 177 266 512 816 1,440 2,940 5,330 8,620 17,700 32,200 50,900500 21 43 82 168 251 484 771 1,360 2,780 5,030 8,150 16,700 30,400 48,100550 20 41 78 159 239 459 732 1290 2,640 4,780 7,740 15,900 28,900 45,700600 19 39 74 152 228 438 699 1240 2,520 4,560 7,380 15,200 27,500 43,600650 18 38 71 145 218 420 669 1180 2,410 4,360 7,070 14,500 26,400 41,800700 17 36 68 140 209 403 643 1140 2,320 4,190 6,790 14,000 25,300 40,100750 17 35 66 135 202 389 619 1090 2,230 4,040 6,540 13,400 24,400 38,600800 16 34 63 130 195 375 598 1060 2,160 3,900 6,320 13,000 23,600 37,300850 16 33 61 126 189 363 579 1020 2,090 3,780 6,110 12,600 22,800 36,100900 15 32 59 122 183 352 561 992 2,020 3,660 5,930 12,200 22,100 35,000950 15 31 58 118 178 342 545 963 1,960 3,550 5,760 11,800 21,500 34,0001,000 14 30 56 115 173 333 530 937 1,910 3,460 5,600 11,500 20,900 33,1001,100 14 28 53 109 164 316 503 890 1,810 3,280 5,320 10,900 19,800 31,4001,200 13 27 51 104 156 301 480 849 1,730 3,130 5,070 10,400 18,900 30,0001,300 12 26 49 100 150 289 460 813 1,660 3,000 4,860 9,980 18,100 28,7001,400 12 25 47 96 144 277 442 781 1,590 2,880 4,670 9,590 17,400 27,6001,500 11 24 45 93 139 267 426 752 1,530 2,780 4,500 9,240 16,800 26,6001,600 11 23 44 89 134 258 411 727 1,480 2,680 4,340 8,920 16,200 25,6001,700 11 22 42 86 130 250 398 703 1,430 2,590 4,200 8,630 15,700 24,8001,800 10 22 41 84 126 242 386 682 1,390 2,520 4,070 8,370 15,200 24,1001,900 10 21 40 81 122 235 375 662 1,350 2,440 3,960 8,130 14,800 23,4002,000 NA 20 39 79 119 229 364 644 1,310 2,380 3,850 7,910 14,400 22,700



Table 8 Pressure of 5 psi (35 kPa), loss of 10 percentPipe Size of Schedule 40

Standard Pipe (in.)

Internal Diameter (in.)

Total Equivalent Length of Pipe (ft)

50 100 150 200 250 300 400 500 1000 1500 20001.00 1.049 1,989 1,367 1,098 940 833 755 646 572 393 316 2701.25 1.380 4,084 2,807 2,254 1,929 1,710 1,549 1,326 1,175 808 649 5551.50 1.610 6,120 4,206 3,378 2,891 2,562 2,321 1,987 1,761 1,210 972 8322.00 2.067 11,786 8,101 6,505 5,567 4,934 4,471 3,827 3,391 2,331 1,872 1,6022.50 2.469 18,785 12,911 10,368 8,874 7,865 7,126 6,099 5,405 3,715 2,983 2,5533.00 3.068 33,209 22,824 18,329 15,687 13,903 12,597 10,782 9,559 6,568 5,274 4,5143.50 3.548 48,623 33,418 26,836 22,968 20,356 18,444 15,786 13,991 9,616 7,722 6,6094.00 4.026 67,736 46,555 37,385 31,997 28,358 25,694 21,991 19,490 13,396 10,757 9,2075.00 5.047 122,544 84,224 67,635 57,887 51,304 46,485 39,785 35,261 24,235 19,461 16,6566.00 6.065 198,427 136,378 109,516 93,732 83,073 75,270 64,421 57,095 39,241 31,512 26,9708.00 7.981 407,692 280,204 225,014 192,583 170,683 154,651 132,361 117,309 80,626 64,745 55,414

10.00 10.020 740,477 508,926 408,686 349,782 310,005 280,887 240,403 213,065 146,438 117,595 100,64612.00 11.938 1,172,269 805,694 647,001 553,749 490,777 444,680 380,588 337,309 231,830 186,168 159,336

Pressure 5.0 PSI (35 kPa)Pressure Drop of 10%

Table 10 Pressure 20 psi (140 kPa), loss of 10 percentPipe Size of Schedule 40

Standard Pipe (in.)

Internal Diameter (in.)


50 100 150 200 250 300 400 500 1000 1500 20001.00 1.049 5,674 3,900 3,132 2,680 2,375 2,152 1,842 1,633 1,122 901 7711.25 1.380 11,649 8,006 6,429 5,503 4,877 4,419 3,782 3,352 2,304 1,850 1,5831.50 1.610 17,454 11,996 9,633 8,245 7,307 6,621 5,667 5,022 3,452 2,772 2,3722.00 2.067 33,615 23,103 18,553 15,879 14,073 12,751 10,913 9,672 6,648 5,338 4,5692.50 2.469 53,577 36,823 29,570 25,308 22,430 20,323 17,394 15,416 10,595 8,509 7,2823.00 3.068 94,714 65,097 52,275 44,741 39,653 35,928 30,750 27,253 18,731 15,042 12,8743.50 3.548 138,676 95,311 76,538 65,507 58,058 52,604 45,023 39,903 27,425 22,023 18,8494.00 4.026 193,187 132,777 106,624 91,257 80,879 73,282 62,720 55,538 38,205 30,680 26,2585.00 5.047 349,503 240,211 192,898 165,096 146,322 132,578 113,370 100,566 69,118 55,505 47,5056.00 6.065 565,926 388,958 312,347 267,329 236,928 214,674 183,733 162,840 111,919 89,875 76,9218.00 7.981 1,162,762 799,160 641,754 549,258 486,797 441,074 377,502 334,573 229,950 184,658 158,043

10.00 10.020 2,111,887 1,451,488 1,165,596 997,600 884,154 801,108 685,645 607,674 417,651 335,388 287,04912.00 11.938 3,343,383 2,297,888 1,845,285 1,579,326 1,399,727 1,268,254 1,085,462 962,025 661,194 530,962 454,435



Standard Pipe (in.)

Internal Diameter

(in.)


50 100 150 200 250 300 400 500 1000 1500 20001.00 1.049 3,259 2,240 1,789 1,539 1,364 1,236 1,058 938 644 517 4431.25 1.380 6,690 4,598 3,692 3,160 2,801 2,538 2,172 1,925 1,323 1,062 9091.50 1.610 10,024 6,889 5,532 4,735 4,197 3,802 3,254 2,884 1,982 1,592 1,3622.00 2.067 19,305 13,268 10,655 9,119 8,082 7,323 6,268 5,555 3,818 3,066 2,6242.50 2.469 30,769 21,148 16,982 14,535 12,882 11,672 9,990 8,854 6,085 4,886 4,1823.00 3.068 54,395 37,385 30,022 25,695 22,773 20,634 17,660 15,652 10,757 8,638 7,3933.50 3.548 79,642 54,737 43,956 37,621 33,343 30,211 25,857 22,916 15,750 12,648 10,8254.00 4.026 110,948 76,254 61,235 52,409 46,449 42,086 36,020 31,924 21,941 17,620 15,0805.00 5.047 200,720 137,954 110,782 94,815 84,033 76,140 65,166 57,755 39,695 31,876 27,2826.00 6.065 325,013 223,379 179,382 153,527 136,068 123,288 105,518 93,519 64,275 51,615 44,1768.00 7.981 667,777 458,959 368,561 315,440 279,569 253,310 216,800 192,146 132,061 106,050 90,765

10.00 10.020 1,212,861 833,593 669,404 572,924 507,772 460,078 393,767 348,988 239,858 192,614 164,85312.00 11.938 1,920,112 1,319,682 1,059,751 907,010 803,866 728,361 623,383 552,493 379,725 304,933 260,983





locating large LPG storage tanks. The lines also have to be purged of air prior to the startup of the facil-ity.

GLOSSARYBtu Abbreviation for British thermal unit, the

quantity of heat required to raise the temperature of one pound of water by one degree Fahrenheit.

Boiling point The temperature of a liquid at which the internal vapor pressure is equal to the external pressure exerted on the surface of the liquid.

Burner A device for the final conveyance of gas, or a mixture of gas and air, to the combustion zone.

Butane (C4H10) A saturated aliphatic hydrocar-bon existing in two isomeric forms and used as a fuel and a chemical intermediate.

Caloric value See heating value.Chimney A vertical shaft enclosing one or more

flues for conveying flue gases to the outside atmo-sphere.

Condensate The liquid that separates from a gas (including flue gas) due to a reduction in tempera-ture.

Cubic foot (meter) of gas The amount of gas that would occupy 1 cubic foot (cubic meter) when at a temperature of 60°F (15.6°C), saturated with water vapor, and under a pressure equivalent to that of 30 in. of mercury (101.3 kPa).

Demand The maximum amount of gas per unit time, usually expressed in cubic feet per hour (liters per minute) or Btu (watts) per hour, required for the operation of the appliance(s) supplied.

Dilution air Air that enters a draft hood or draft regulator and mixes with the flue gases.

Diversity factor The ratio of the maximum prob-able demand to the maximum possible demand.

Draft hood A device built into an appliance, or made a part of the vent connector from an appli-ance, that is designed to:


Standard Pipe (in.)

Internal Diameter

(in.)


50 100 150 200 250 300 400 500 1000 1500 20001.00 1.049 12,993 8,930 7,171 6,138 5,440 4,929 4,218 3,739 2,570 2,063 1,7661.25 1.380 26,676 18,335 14,723 12,601 11,168 10,119 8,661 7,676 5,276 4,236 3,6261.50 1.610 39,970 27,471 22,060 18,881 16,733 15,162 12,976 11,501 7,904 6,348 5,4332.00 2.067 76,977 52,906 42,485 36,362 32,227 29,200 24,991 22,149 15,223 12,225 10,4632.50 2.469 122,690 84,324 67,715 57,955 51,365 46,540 39,832 35,303 24,263 19,484 16,6763.00 3.068 216,893 149,070 119,708 102,455 90,804 82,275 70,417 62,409 42,893 34,445 29,4803.50 3.548 317,564 218,260 175,271 150,009 132,950 120,463 103,100 91,376 62,802 50,432 43,1644.00 4.026 442,393 304,054 244,166 208,975 185,211 167,814 143,627 127,294 87,489 70,256 60,1305.00 5.047 800,352 550,077 441,732 378,065 335,072 303,600 259,842 230,293 158,279 127,104 108,7846.00 6.065 1,295,955 890,703 715,266 612,175 542,559 491,598 420,744 372,898 256,291 205,810 176,1478.00 7.981 2,662,693 1,830,054 1,469,598 1,257,785 1,114,752 1,010,046 864,469 766,163 526,579 422,862 361,915

10.00 10.020 4,836,161 3,323,866 2,669,182 2,284,474 2,024,687 1,834,514 1,570,106 1,391,556 956,409 768,030 657,33412.00 11.938 7,656,252 5,262,099 4,225,651 3,616,611 3,205,335 2,904,266 2,485,676 2,203,009 1,514,115 1,215,888 1,040,643

Table 12 Specific Gravity Multipliers

Specific Gravity

Capacity Multiplier

Specific Gravity

Capacity Multiplier

Specific Gravity

Capacity Multiplier

0.35 1.310 0.75 0.895 1.40 0.6550.40 1.230 0.80 0.867 1.50 0.6330.45 1.160 0.85 0.841 1.60 0.6120.50 1.100 0.90 0.817 1.70 0.5940.55 1.040 1.00 0.775 1.80 0.5770.60 1.000 1.10 0.740 1.90 0.5650.65 0.962 1.20 0.707 2.00 0.5470.70 0.926 1.30 0.680 2.10 0.535

Table 13 Conversion of Gas Prcssurc to Various Designations

kP

Equivalent inches

Pressure per square inch

Equivalent inches

Pressure per square inch

kPWater Mercury Pounds Ounces Water Mercury Pounds Ounces0.002 0.01 0.007 0.0036 0.0577 8.0 0.588 0.289 4.62 2.00.05 0.20 0.015 0.0072 0.115 9.0 0.662 0.325 5.20 2.20.07 0.30 0.022 0.0108 0.1730.10 0.40 0.029 0.0145 0.231 10.0 0.74 0.361 5.77 2.5

11.0 0.81 0.397 6.34 2.70.12 0.50 0.037 0.0181 0.239 12.0 0.88 0.433 3.00.15 0.60 0.044 0.0217 0.346 13.0 0.96 0.469 7.50 3.20.17 0.70 0.051 0.0253 0.4040.19 0.80 0.059 0.0289 0.462 13.6 1.00 0.491 7.86 3.370.22 0.90 0.066 0.0325 0.520 13.9 1.02 0.500 8.00 3.4

14.0 1.06 0.505 8.08 3.50.25 1.00 0.074 0.036 0.5770.3 1.36 0.100 0.049 0.785 15.0 1.10 0.542 8.7 3.70.4 1.74 0.128 0.067 1.00 16.0 1.18 0.578 9.2 4.00.5 2.00 0.147 0.072 1.15 17.0 1.25 0.614 9.8 4.20.72 2.77 0.203 0.100 1.60 18.0 1.33 0.650 10.4 4.50.76 3.00 0.221 0.109 1.73 19.0 1.40 0.686 10.9 4.71.0 4.00 0.294 0.144 2.31

20.0 1.47 0.722 11.5 5.01.2 5.0 0.368 0.181 2.89 0.903 14.4 6.21.5 6.0 0.442 0.217 3.46 25.0 1.84 0.975 15.7 6.71.7 7.0 0.515 0.253 4.04 27.2 2.00 1.00 16.0 6.9

27.7 2.03



1. Provide for the ready escape of the flue gases from the appliance in the event of no draft, backdraft, or stoppage beyond the draft hood.

2. Prevent a backdraft from entering the appliance.

3. Neutralize the effect of stack action of the chimney or gas vent upon the operation of the appliance.

Excess air Air that passes through the combustion chamber and the appliance flues in excess of that which is theoretically required for complete combustion.

Flue gases The products of combustion plus the excess air in appliance flues or heat exchangers (before the draft hood or draft regulator).

Fuel gas A gaseous compound used as fuel to generate heat. It may be known variously as utility gas, natural gas, liquefied petero-leum gas, propane, butane, methane, or a combination of the above. It has a caloric value that corresponds to the specific compound or combination of compounds. Care must be exercised in determin-ing the caloric value for design purposes.

Gas log An unvented, open-flame-type room heater consisting of a metal frame or base supporting simulated logs designed for installation in a fireplace.

Gas train A series of devices pertaining to a fuel gas appliance located on the upstream side of the unit. Typically, it consists of a combination of devices and may include pipe, fittings, fuel, air-supervisory switches (e.g., pressure regulators), and safety shutoff valves.

Gas-train vent A piped vent to atmosphere from a device on a gas train.

Gas vents Factory-built vent piping and vent fittings listed by a nationally recognized testing agency, assembled and used in accor-dance with the terms of their listings, used for conveying flue gases to the outside atmosphere.

1. Type B gas vent. A gas vent for venting gas appliances with draft hoods and other gas appliances listed for use with type B gas vents.

2. Type B-W gas vent. A gas vent for venting listed gas-fired vented wall furnaces.

3. Type L vent. A gas vent for venting gas appliances listed for use with type L vents.

Heating value (total) The number of British thermal units produced by the combustion, at constant pressure, of 1 cubic foot (cubic meter) of gas when the products of combustion are cooled to the initial temperature of the gas and air; the water vapor formed during combustion is condensed; and all the necessary corrections have been applied.

LPG Liquefied petroleum gas, a mixture of propane and butane.

Loads, connected The sum of the rated Btu input to individual gas utilization equipment connected to a piping system. May be expressed in cubic feet (cubic meters) per hour.

Meter set assembly The piping and fittings installed by the serv-ing gas supplier to connect the inlet side of the meter to the gas ser-vice and the outlet side of the meter to the customer’s building or yard piping.

Pipe, equivalent length The resistance of valves, controls, and fittings to gas flow, expressed as equivalent length of straight pipe.

Pressure drop The loss in static pressure due to friction or obstruction during flow through pipe, valves, fittings, regulators, and burners.

Propane (C3H8) A gaseous hydrocarbon of the methane series, found in petroleum.

Regulator, gas pressure A device for controlling and maintain-ing a uniform gas pressure. This pressure is always lower than the supply pressure at the inlet of the regulator.

Safety shutoff device A device that is designed to shut off the gas supply to the controlled burner(s) or appliance(s) in the event that the source of ignition fails. This device may interrupt the flow of gas to the main burner(s) only or to the pilot(s) and main burner(s) under its supervision.

Specific gravity The ratio of the weight of a given volume of gas to that of the same volume of air, both measured under the same conditions.

Vent connector That portion of the venting system that connects the gas appliance to the gas vent, chimney, or single-wall metal pipe.

Vent gases The products of combustion from a gas appliance plus the excess air and the dilution air in the venting system above the draft hood or draft regulator.

REFERENCES

Table 14 100% Propane for Interior PipingNominal

Inside 1⁄2 3⁄4 1 11⁄4 11⁄2 2 21⁄2 3 4Actual 0.622 0.824 1.049 1.380 1.610 2.067 2.469 3.068 4.026

Lenth (ft) Capacity in Thousands of Btu per Hour10 291 608 1,150 2,350 3,520 6,790 10,800 19,100 39,00020 200 418 787 1,620 2,420 4,660 7,430 13,100 26,80030 160 336 632 1,300 1,940 3,750 5,970 10,600 21,50040 137 287 541 1,110 1,660 3,210 5,110 9,030 18,40050 122 255 480 985 1,480 2,840 4,530 8,000 16,30060 110 231 434 892 1,340 2,570 4,100 7,250 14,80080 101 212 400 821 1,230 2,370 3,770 6,670 13,600

100 94 197 372 763 1,140 2,200 3,510 6,210 12,700125 89 185 349 716 1,070 2,070 3,290 5,820 11,900150 84 175 330 677 1,010 1,950 3,110 5,500 11,200175 74 155 292 600 899 1,730 2,760 4,880 9,950200 67 140 265 543 814 1,570 2,500 4,420 9,010250 62 129 243 500 749 1,440 2,300 4,060 8,290300 58 120 227 465 697 1,340 2,140 3,780 7,710350 51 107 201 412 618 1,190 1,900 3,350 6,840400 46 97 182 373 560 1,080 1,720 3,040 6,190450 42 89 167 344 515 991 1,580 2,790 5,700500 40 83 156 320 479 922 1,470 2,600 5,300550 37 78 146 300 449 865 1,380 2,440 4,970600 35 73 138 283 424 817 1,300 2,300 4,700650 33 70 131 269 403 776 1,240 2,190 4,460700 32 66 125 257 385 741 1,180 2,090 4,260750 30 64 120 246 368 709 1,130 2,000 4,080800 29 61 115 236 354 681 1,090 1,920 3,920850 28 59 111 227 341 656 1,050 1,850 3,770900 27 57 107 220 329 634 1,010 1,790 3,640950 26 55 104 213 319 613 978 1,730 3,530

1,000 25 53 100 206 309 595 948 1,680 3,4201,100 25 52 97 200 300 578 921 1,630 3,3201,200 24 50 95 195 292 562 895 1,580 3,2301,300 23 48 90 185 277 534 850 1,500 3,0701,400 22 46 86 176 264 509 811 1,430 2,9301,500 21 44 82 169 253 487 777 1,370 2,8001,600 20 42 79 162 243 468 746 1,320 2,6901,700 19 40 76 156 234 451 719 1,270 2,5901,800 19 39 74 151 226 436 694 1,230 2,5001,900 18 38 71 146 219 422 672 1,190 2,4202,000 18 37 69 142 212 409 652 1,150 2,350

100% Propane, Pressure 11 in wc, Pressure Drop 0.5 in wc




1. American Society of Heating, Refrigerating and Air Condition-ing Engineers. Handbooks. Fundamentals and Equipment Vols. Latest ed. New York.

2. American Society of Mechanical Engineers (ASME). Fuel gas piping. ASME B31.2.

3. Ingersoll-Rand Company. 1969. Compressed air and gas data. New York.

4. International Association of Plumbing and Mechanical Officials (IAPMO) Code.

5. n.a. 1994. Mechanical engineering reference manual. 9th ed. Professional Publications.

6. Mohinder Nayer ed, . 1998. Piping handbook. New York: McGraw-Hill.

7. National Fire Protection Association. Cutting and welding pro-cesses. NFPA 51B. Boston, Mass.

8. National Fire Protection Association (NFPA). LP-gases at utility gas plants. NFPA 59. Boston Mass.

9. National Fire Protection Association. National fuel gas code. NFPA 54. Boston, Mass.

10. National Fire Protection Association. Oxygen-fuel gas systems for weldings and cuttings. NFPA 51. Boston.

11. National Fire Protection Association. Powered indus-trial trucks. NFPA 505. Boston.

12. U.S. Army Corps of Engineers manual. EM-1110-34-166.

13. Frankel, M., Facility Piping Systems Handbook, 2002, McGraw Hill, New York City

The material reproduced from the NFPA is not the offi-cial and complete position of the NFPA on the referenced subject which is presented only by the standard in its entirety.

Table 15 100% Propane for Site MainsNominal

Inside 1⁄2 3⁄4 1 11⁄4 11⁄2 2 21⁄2 3 4Actual 0.622 0.824 1.049 1.380 1.610 2.067 2.469 3.068 4.026

Lenth (ft) Capacity in Thousands of Btu per Hour10 5,890 12,300 23,200 47,600 71,300 137,000 219,000 387,000 789,00020 4,050 8,460 15,900 32,700 49,000 94,400 150,000 266,000 543,00030 3,250 6,790 12,800 26,300 39,400 75,800 121,000 214,000 436,00040 2,780 5,810 11,000 22,500 33,700 64,900 103,000 183,000 373,00050 2,460 5,150 9,710 19,900 29,900 57,500 91,600 162,000 330,00060 2,230 4,670 8,790 18,100 27,100 52,100 83,000 147,000 299,00070 2,050 4,300 8,090 16,600 24,900 47,900 76,400 135,000 275,00080 1,910 4,000 7,530 15,500 23,200 44,600 71,100 126,000 256,00090 1,790 3,750 7,060 14,500 21,700 41,800 66,700 118,000 240,000

100 1,690 3,540 6,670 13,700 20,500 39,500 63,000 111,000 227,000125 1,500 3,140 5,910 12,100 18,200 35,000 55,800 98,700 201,000150 1,360 2,840 5,360 11,000 16,500 31,700 50,600 89,400 182,000175 1,250 2.620 4,930 10,100 15,200 29,200 46,500 82,300 167,800200 1,160 2,430 4,580 9,410 14,100 27,200 43,300 76,500 156,100250 1,030 2,160 4,060 8,340 12,500 24,100 38,400 67,800 138,400300 935 1,950 3,680 7,560 11,300 21,800 34,800 61,500 125,400350 860 1,800 3,390 6,950 10,400 20,100 32,000 56,500 115,300400 800 1,670 3,150 6,470 9,690 18,700 29,800 52,600 107,300450 751 1,570 2,960 6,070 9,090 17,500 27,900 49,400 100,700500 709 1,480 2,790 5,730 8,590 16,500 26,400 46,600 95,100550 673 1,410 2,650 5,450 8,160 15,700 25,000 44,300 90,300600 642 1,340 2,530 5,200 7,780 15,000 23,900 42,200 86,200650 615 1,290 2,420 4,980 7,450 14,400 22,900 40,500 82,500700 591 1,240 2,330 4,780 7,160 13,800 22,000 38,900 79,300750 569 1,190 2,240 4,600 6,900 13,300 21,200 37,400 76,400800 550 1,50 2,170 4,450 6,660 12,800 20,500 36,200 73,700850 532 1,110 2,100 4,300 6,450 12,400 19,800 35,000 71,400900 516 1,080 2,030 4,170 6,250 12,000 19,200 33,900 69,200950 501 1,050 1,970 4,050 6,070 11,700 18,600 32,900 67,200

1,000 487 1,020 1,920 3,940 5,900 11,400 18,100 32,000 65,4001,100 463 968 1,820 3,740 5,610 10,800 17,200 30,400 62,1001,200 442 923 1,740 3,570 5,350 10,300 16,400 29,000 59,2001,300 423 884 1,670 3,420 5,120 9,870 15,700 27,800 56,7001,400 406 849 1,600 3,280 4,920 9,480 15,100 26,700 54,5001,500 391 818 1,540 3,160 4,740 9,130 14,600 25,700 52,5001,600 378 790 1,490 3,060 4,580 8,820 14,100 24,800 50,7001,700 366 765 1,440 2,960 4,430 8,530 13,600 24,000 49,0001,800 355 741 1,400 2,870 4,300 8,270 13,200 23,300 47,6001,900 344 720 1,360 2,780 4,170 8,040 12,800 22,600 46,2002,000 335 700 1,320 2,710 4,060 7,820 12,500 22,000 44,900

100% PropanePressure 10 PSI (70 kPa)Pressure Loss 3.0 PSI (21 kPa)



about this issue’s articlethe January/february 2008 continuing education article is

“fuel Gas piping systems,” chapter 7 of Plumbing Engineering Design Handbook, Volume 2: Plumbing Systems.

this chapter describes fuel gas systems on consumer sites from the property line to the final connection with the most remote gas appliance or piece of equip ment. the system is intended to provide sufficient pressure and volume for all uses. since natural gas (nG) is a nonrenewable energy resource, the engineer should design for its efficient use. the direct utilization of nG is preferable to the use of electrical energy when electric-ity is obtained from the combustion of gas or oil. however, in many areas, the gas supplier and/or governmental agencies may impose regulations that restrict the use of natural gas.

you may locate this article at www.psdmagazine.org. read the article, complete the following exam, and submit your an-swer sheet to the aspe office to potentially receive 0.1 ceu.

psd

144

continuing education from Plumbing Systems & Designdiane m. wingard, cpd

ce Questions—“fuel Gas piping systems” (psd 144)1. The maximum allowable operating pressure for NG

piping inside a building is ______.a. 0.5 psigb. determined by the authority having jurisdictionc. 5.0 psigd. no limit

2. Which of the following is true when installing a pressure regulator?a. if located indoors, a relief vent may be required.b. it is provided to reduce the pressure of the incoming

service to a safe operating pressure at the appliance.c. it normally is located outside before the meter.d. all of the above are true.

3. NG systems should be designed with an allowable pressure drop of ______.a. 0.2–0.5 inch w.c.b. 5.0 inches w.c.c. 10 psid. none of the above

4. Which of the following is an acceptable material for fuel gas piping?a. black steelb. type l copperc. corrugated stainless steel tubingd. all of the above

5. LP gas can be stored in tanks at a pressure of ______.a. 300 psi, b. 150 psi, c. 250 psi, d. 1,000 psi

6. Which of the following is true for a fuel gas system?a. the flow rate of an appliance is equal to the

consumption divided by 1,000.b. natural gas is stored on site in large tanks.c. Gas systems always should be vented.d. Gas that is vented through regulators can always

discharge into occupied space.

7. LPG ______.a. needs to be alarmed when installed in crawl spacesb. is heavier than airc. vents shall be terminated a minimum of 3 feet

horizontally from an openingd. slope on grade at the site

8. The purpose of a gas booster is ______.a. to increase the volumetric supplyb. to increase the pressurec. to maintain the pressure delivered by the supplierd. none of the above

9. When providing a booster, ______.a. it is important to provide a regulator to protect the

appliances from high pressure during times of low demand

b. the equipment needs to be shut down during low demand periods

c. it needs to be located outside of the buildingd. it is sized and provided by the gas supplier

10. Which of the following is required to size a system?a. allowable friction lossb. pipe layoutc. probable demandd. all of the above

11. Which standard is referenced for fuel gas systems?a. nfpa 99b. nfpa 101c. nfpa 54d. nfpa 13

12. Large LPG tanks must be located ______.a. away from the building in case of leaksb. near the appliances being servedc. inside the building in a fire-rated enclosured. underground


now online!The technical article you must read to complete the exam is located at www.psdmagazine.org. Just click on “Plumbing Systems & Design Con-tinuing Education Article and Exam” at the top of the page. The follow-ing exam and application form also may be downloaded from the website. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. If you earn a grade of 90 percent or high-er on the test, you will be notified that you have logged 0.1 CEU, which can be applied toward CPD renewal or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for three years.Note: In determining your answers to the CE questions, use only the material presented in the corresponding continuing education article. Using information from other materials may result in a wrong answer.



Plumbing Systems & Design continuing education application formthis form is valid up to one year from date of publication. the PS&D continuing education program is approved by aspe for up to one contact hour (0.1 ceu) of credit per article. participants who earn a passing score (90 percent) on the ce questions will receive a letter or certification within 30 days of aspe’s receipt of the application form. (no special certificates will be issued.) participants who fail and wish to retake the test should resubmit the form along with an additional fee (if required).

1. photocopy this form or download it from www.psdmagazine.org.

2. print or type your name and address. be sure to place your aspe membership number in the appropriate space.

3. answer the multiple-choice continuing education (ce) questions based on the corresponding article found on www.psdmagazine.org and the appraisal questions on this form.

4. submit this form with payment ($35 for nonmembers of aspe) if required by check or money order made payable to aspe or credit card via mail (aspe education credit, 8614 w. catalpa ave., suite 1007, chicago, il 60656) or fax (773-695-9007).

please print or type; this information will be used to process your credits.

name _______________________________________________________________________________________________________

title _________________________________________________aspe membership no. _____________________________________

organization _________________________________________________________________________________________________

billing address ________________________________________________________________________________________________

city _________________________________________ state/province_________________________ zip _____________________

country ______________________________________________ e-mail __________________________________________________

daytime telephone ____________________________________ fax ____________________________________________________

PS&D Continuing Education Answer SheetFuel Gas Piping Systems (PSD 144)

Questions appear on page 18. Circle the answer to each question. Q 1. A B C D Q 2. A B C D Q 3. A B C D Q 4. A B C D Q 5. A B C D Q 6. A B C D Q 7. A B C D Q 8. A B C D Q 9. A B C D Q 10. A B C D Q 11. A B C D Q 12. A B C D

Appraisal QuestionsFuel Gas Piping Systems (PSD 144)

1. Was the material new information for you? Yes No

2. Was the material presented clearly? Yes No

3. Was the material adequately covered? Yes No

4. Did the content help you achieve the stated objectives? Yes No

5. Did the CE questions help you identify specific ways to use ideas presented in the article? Yes No

6. How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)? __________________


i certify that i have read the article indicated above.

signature

expiration date: continuing education credit will be givenfor this examination through JANUARY 31, 2009.applications received after that date will not be processed.

aspe member nonmemberEach examination: $25 Each examination: $35Limited Time: No Cost to ASPE Member

payment: personal check (payable to aspe) $ ___________ business or government check $ ________ DiscoverCard VISA MasterCard AMEX $ ___________

If rebilling of a credit card charge is necessary, a $25 processing fee will be charged.aspe is hereby authorized to charge my ce examination fee to my credit card

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signature cardholder’s name (please print)



PSD

132

Plumbing Design for Health Care Facilities


MARCH/APRIL 2006

PSDMAGAZINE.ORG


InTroDuCTIonHealth-care facilities, nursing homes, medical schools,and medical laboratories require plumbing systems thataremorecomplexthanthoseformostothertypesofbuild-ing. The plumbing designer should work closely with thearchitectandfacilitystaffandbeinvolvedinmeetingsanddiscussionsinordertofullyunderstandtheplumbingrequire-mentsforanyneworspecialmedicalequipment.Theplumb-ing design must be coordinated with the civil, architectural,structural, mechanical, and electrical designs to ensure thatadequate provisions have been made for utility capacities, forthenecessaryclearancesandspacerequirementsofthepipingsystemsandrelatedplumbingequipment,andforcompliancewithapplicablecodes.Health-carefacilitiesmayhavedifferentrequirements or be exempt from some codes and standards,such as water and energy conservation codes and regulationsregarding the physically challenged. The plumbing engineershould consult with the administrative authority in order toensureconformancewithlocalordinances.

This chapter discusses the provisions that may be encoun-teredbytheplumbingprofessionalinthedesignofahealth-carefacility, includingthe following:plumbingfixturesandrelatedequipment,thesanitarydrainagesystem,thewater-supplysys-tem, laboratory waste and vent systems, pure-water systems,andmedical-gassystems.

PLuMBInGFIxTurESAnDrELATEDEquIPMEnT

SELECTIonProCESSMeetingsoftheplumbingengineerwiththearchitectandthefacilitystafftodiscussthegeneralandspecificrequirementsregardingtheplumbingfixturesandrelatedequipmentareusuallyheldafterthearchitecthaspreparedthepreliminarydrawings.Atthesemeetings,theplumbingdesignershouldassistintheselectionofplumbingfixtures.Followingthesesessions,theplumbingdesignercanpreparethepreliminarydrawingsandcoordinatewiththearchitectandfacilitystafftherequiredpipingsystemsandtheplumbingfixturespacere-quirements.Indetailingthepipingsystemspacesandplumb-ingfixturelocations,theplumbingengineershouldrefertotheframingdrawings.Itiscommonforthearchitecttolocatethepipingshaftsandthespacesindirectconflictwiththeframing;itistheplumbingdesigner’sresponsibilitytogivethearchitectdirectionsregardingthespacerequirements,fixturearrangement,andpipe-shaftsizeandlocations.

Followingthemeetingsheldwith thearchitectandhospitalstaff,andwiththepreliminarydrawingsavailable,theplumbingdesignershouldprepareanoutlinespecificationfortheplumb-ing fixtures and related equipment. A guide to the required

plumbing fixtures and equipment for health-care facilities isprovidedinTable1andisdiscussedlaterinthissection.

Areviewofapplicablecoderequirementsregardingthequalityandtypesofplumbingfixturesisalwaysrequired.Inadditiontothelocalcodes,itisnecessaryfortheplumbingengineertorefertothespecialhospitalcoderequirementspublishedbythelocalhospital authorities, the state hospital or health-departmentauthorities,theJointCommissionfortheAccreditationofHos-pitalsOrganization(JCAHO),andtheUSDepartmentofHealthandHumanServices.Thearchitectmayinvestigatethesespe-cial requirements; however, the plumbing designer must befamiliar with them since they contain many other applicablerequirements(inadditiontothetableindicatingtheplumbingfixturesnecessaryforaparticularinstallation).

GEnErALrEquIrEMEnTSPlumbing fixtures in health-care facilities should be of dense,imperviousmaterialshavingsmoothsurfaces.Plumbingfixturesof vitreous china, enameled cast iron, and stainless steel arecommonlyused.Fixturebrass—includingfaucets,traps,strain-ers, escutcheons, stops, and supplies—should be chromiumplated in a manner approved by the administrative author-ity. Die-cast metals should not be used. Faucets should havea laminar flow device (no alternative) of brass, Monel metal,or stainless-steel trim. Each plumbing fixture in health-carefacilitiesshouldbeprovidedwith individualstopvalves.Eachwater-service main, branch main, and riser shall have valves.Accessshallbeprovidedatallvalves.Allsubmergedinlets,fau-cetswithhoseadapters,andflushvalvesmustbeequippedwithapprovedvacuumbreakers.Backflow-preventiondevicesshallbeinstalledonhosebibbs,supplynozzlesusedfortheconnec-tionofhosesortubing,andatotherlocationswherethepotablewatersupplymustbeprotectedfromcontamination.

Allplumbingfixtures,faucets,piping,solder,andfluxesusedinpotentialdrinking-waterareasshouldcomplywiththelatestmaximumleadcontentregulations.FacilitiesforthephysicallychallengedshallbeincompliancewiththeAmericanswithDis-abilitiesAct(ADA)accessibilityguidelines.

FIxTurESForSPECIFICHEALTH-CArEArEASGeneral-use staff and public areasWater closets Vitreouschina,siphon-jetwaterclosetwithelon-gated bowl design with open-front seat, less cover, should bespecified.Wall-hungwaterclosetsarepreferredforeasyclean-ing;however,floor-setmodelsarealsoacceptablebymostlocaljurisdictions. All water closets should be operated by water-saverflushvalves.

Lavatories and sinks Vitreous china, enameled cast ironorstainless-steel lavatoriesandsinksshouldbespecified.Themostcommonlyspecifiedsize is20×18×7½in.deep(508×457.2 × 190.5 mm deep). Hands-free controls (foot or knee

ConTInuInG EDuCaTIon

Plumbing Design forHealth Care Facilities

Reprinted from American Society of Plumbing Engineers Data Book Volume 3: Special Plumbing Systems, Chapter 2: “Plumbing Design for Health Care Facilities.” ©2000, American Society of Plumbing Engineers.

PlumbingSystems&Design MARCH/APRIL 2006 PSDMAGAZINE.ORG


controls) are generally employed for staff use and for scrub-up sinks. In public areas, codes should be checked for the require-ment of self-closing valves and/or metered valves. Stops should be provided for all supply lines. Aerators are not permitted; use laminar flow devices. Insulated and/or offset p-traps should be used for handicapped fixtures.

Faucets Valves should be operable without hands, i.e., with wrist blades or foot controls or electronically. If wrist blades are used, blade handles used by the medical and nursing staff, patients, and food handlers shall not exceed 4½ in. (11.43 cm) in length. Handles on scrub sinks and clinical sinks shall be at least 6 in. (15.24 cm) long. Water spigots used in lavatories and sinks shall have clearances adequate to avoid contaminating utensils and the contents of carafes, etc.

Urinals Vitreous china wall-hung urinals with flush valves. Flush valves should be equipped with stops and may be of the exposed or concealed design.

Showers The shower enclosures and floor specified by the plumbing engineer may be constructed of masonry and tile or of prefabricated fiberglass. Showers and tubs shall have nonslip walking surfaces. The shower valve should automatically com-pensate for variations in the water-supply pressure and tem-perature to deliver the discharge water at a set temperature that will prevent scaldings.

Drinking fountains and water coolers Drinking fountains are available in vitreous china, steel and stainless steel. Units for exterior installations are available in suitable materials. Refrig-erated water coolers are available in steel or stainless steel. All of these materials are acceptable by most local administrative

Table 1 Recommended Plumbing Fixtures and Related EquipmentMedical-Care AreasPublic/Staff Restrooms l l l l l l l

Staff Lounge l l l l l l

Patient Rooms l l l l

Isolation Rooms l l l l

Nurse Stations l

Nursery l l

Formula Room l l l

Intensive-Care Room l l l

Outpatient-Services Area l l l l

Emergency Rooms l l l l l

Exam/Treatment Room l l l

Labor Room l l l

Janitor’s Closet l l l

Clean Linen Holding l

Soiled Linen Holding l l

Nourishment Station l l l

Patient Bathing Area l l l l l

Critical-Care Area l l l l l

Pharmacy l

Surgical Scrub-up l

Anesthesia Workroom l

Surgical Supply Services l

Surgical Cleanup Room l

Doctors’ Locker Room l l l l

Nurses’ Locker Room l l l

Recovery Room l l l

Fracture Room l l

Cleanup/Utility Room l l l l

Sub-Sterilizing Room l

Medical Laboratory l l l l l l l l l l l

Physical Therapy Room l l l l l l l

Cystoscopic Room l l l l l l

Autopsy Room l l l l l l l l

Dietary Services l l l l l l l l l l

Laundry Facility l l l l

Family Waiting Room l l l

Elong

ated

Wat

er Cl

oset

, Flu

shVa

lve

Urin

al

Hand

wash

ing L

avat

ory

Show

er

Drin

king F

ount

ain / W

ater

Cool

er

Mop

Serv

ice B

asin

Coun

ter S

ink,

Singl

e Com

partm

ent

Coun

ter S

ink,

Doub

le Co

mpa

rtmen

t

Clin

ic Sin

k, Flu

shin

g Rim

Scru

b-up

Sink

Utilit

y Sin

k

Sink,

Tripl

e Com

partm

ent

Plas

ter S

ink,

Plas

ter T

rap

Cup S

ink

Floor

Dra

in

Floor

Dra

in, F

lush

ing R

im

Emer

genc

y Sho

wer

Emer

genc

y Eye

wash

Bath

tub /

Show

er

Sitz B

ath

Bedp

an W

ashe

r

Was

te G

rinde

r

Ice M

aker

Arm

/ Le

g Bat

h

Imm

ersio

n Ba

th

Glas

s Was

her

Infa

nt B

atht

ub

MARCH/APRIL 2006 Plumbing Systems & Design 57


ConTInuInG EDuCaTIon: Plumbing Design for health Care Facilities

authorities.Theseunitsmaybeofthesurface-mounted,semi-recessedorfully-recesseddesign.

Chilled water for drinking purposes should be providedbetween 45 and 50°F (7.2 and 10.0°C) and obtained by chill-ingwaterwitharefrigerationcompressor.Thecompressormaybe enclosed in a cabinet with the dispenser (water cooler),installedinawallcavitybehindagrilladjacenttothedispenser,orremotelylocatedforsingleormultipledispensers.Aremotelyinstalled unit for multiple dispensers (central system) shouldhavearecirculationsystem.

Mop-service basins Floor-mounted mop-service basinscanbeobtained inprecast or (terazzo)molded-stone unitsofvarious sizes. The plumbing engineer should specify the mostsuitablemodel.Rimguardsarenormallyprovidedtoprotecttherimsfromdamageandwallguardsareprovidedtoprotectwallsfromsplashingandchemicalstains.Thewater-supplyfixtureisusuallyatwo-handlemixingfaucetmountedonthewallwithawallbrace,vacuumbreaker,andhoseadapter.

Floor drains Floordrainsintoiletroomsareoptionalinmostcases;however,therearemanyinstanceswherethefloordrainsare required by the applicable codes. The plumbing designershouldgiveconsiderationtomaintainingatrapsealinthefloordrain through the use of deep-seal p-traps and/or trap prim-ers.Floordrainsshallnotbeinstalledinoperatinganddeliveryrooms.

Patient rooms Theserooms(privateorsemiprivate)usuallyareprovidedwithatoiletroomcontainingawatercloset,alava-tory, and a shower or bathtub. (Some hospitals use commonshower and bath facilities for a group of patient rooms.) Theplumbing fixtures should conform with the following recom-mendations:

Thewaterclosetshouldbevitreouschina,wall-hungorfloor-mounteddesign,withanelongatedbowl.Allwaterclosetsshouldbe operated by a flush valve. Water closets should have open-frontseats,lesscover.Bedpanlugsandbedpanwashersareoftenrequired by the local codes. Bedpan-flushing devices shall beprovided in each inpatient toilet room; however, installation isoptional inpsychiatricandalcohol-abuseunits,wherepatientsareambulatory.

Thelavatoryshouldbeaminimumof20×18×7½in. (508×457.2×190.5mm)deep.Lavatoriesshouldbeinstalledatleast34in. (863.6 mm) above the floor. Mixing faucets should be of thegooseneck-spout design and provided with wrist-blade handles,electronic,orhands-freecontrols.

Theshowerisusuallyconstructedofmasonryandtile,acrylics,orfiberglass.Theshowerbasesshouldbenonslipsurfaces.Theshowervalveshouldautomaticallycompensateforvariationsinthe water-supply pressure and temperature to deliver the dis-chargewateratasettemperaturethatwillpreventscalding.Grabbars,locatedwithintheshowerenclosure,areusuallyrequiredbythelocalcodes.Theplumbingengineershouldalwayscheckwiththelocaladministrativeauthorityregardingapproveddesigns.

Bathtubs can be constructed of cast iron, fiberglass, acryl-ics,orsteel.Faucetsshouldbeastheyareforshowers.Showerheads may be of the stationary design, but in many locationshand-heldshowersarerequired.

Alavatoryintendedforusebydoctors,nurses,andotherhos-pital staff is sometimes required by the local ordinances. Thisparticularlavatoryisusuallylocatedonthewallnearthedoorwithagooseneckspoutandhands-freecontrols.

A water closet and lavatory, with a fixed or fold-away waterclosetmadeofstainlesssteel,maybeconsidered.Thisconcept,aswellastheconstructionoftheunit,mustbeacceptedbytheadministrativeauthority.

Ward rooms Wardroomsareinfrequentlyfoundinhealth-care facilities, particularly in the private hospital field. Theseroomsrequireatleast1lavatory.Thislavatoryshouldbeamini-mum20×18in.(508×457.2mm)andmadeofvitreouschinaorstainlesssteel.Thefaucetshouldbeofthegooseneck-spoutdesign and provided with wrist-blade handles or hands-freecontrols.

Nurseries The hospital’s nursery is usually provided with aminimumsize20×18in.(508×457.2mm)lavatorywithhands-freecontrolsandahighgooseneckspout.Aninfant’sbathtub,wall-orcounter-mountedwithanintegrallargedrainboardandrinsingbasin,isprovided.Water-supplyfittingsarefillerspoutsover the basins with separate hand-valve controls. The spoutand the spray are usually supplied and controlled through athermostatic mixing valve. The ultimate in maintaining a safewatertemperatureisaseparatesupplytank.

Intensive-care rooms Theseroomsusuallyhaveutilitysinkswithhands-freecontrolswithhighgooseneckspouts.Awater-supplyfittingequippedwithagooseneckspoutandprovisionforbedpanwashing(eitheratanimmediatelyadjacentwaterclosetorataseparatebedpanwashingstationwithinanenclosureinthe room) should be provided. Newer designs have includedcombinationlavatory/waterclosetsforpatientuse,especiallyincardiac-careunits.

Emergency (triage) rooms Theplumbingfixturesprovidedinemergencyroomsincludeautilitysinkwithanintegraltrayand a water-supply fitting with a gooseneck spout and wrist-blade handles. A vitreous china clinic sink (or a flushing-rimsink), for the disposal of solids, with the water-supply fittingconsisting of a flush valve and a separate combination faucetwithvacuumbreakermountedonthewallabovetheplumbingfixture,shouldalsobeprovided.

Examination and treatment rooms These rooms are usu-ally provided with vitreous china or stainless-steel lavatories.Thewater-supplyfittingshouldbeahands-freevalveequippedwithahigh, rigid,gooseneckspout.Foraparticularexamina-tionroomoragroupofpatientrooms,anadjacenttoiletroomisprovidedcontainingaspecimen-typewaterclosetforinsertingaspecimen-collectingbedpan.Thetoiletroomalsorequiresalavatoryandawatersupplywithwrist-bladehandlesorhands-freecontrolsandwithagooseneckspout.

Physical-therapy treatment rooms The plumbing fixturesandrelatedequipmentfortheseroomsusuallyincludehydro-therapyimmersionbathsandleg,hip,andarmbaths.Theseunitsare generally furnished with electric-motor-driven whirlpoolequipment.Thewaterisintroducedintothestainless-steeltankenclosurebymeansofa thermostaticcontrolvalvetopreventscalding,usuallywallmountedadjacenttothebathforopera-tionbyahospitalattendant.Thewatersupplyshouldbesizedtominimizetubfilltime.Theimmersionbathsareusuallypro-videdwithoverheadhoistsandcanvasslingsforfacilitatingtheliftinginandoutofthebathofacompletelyimmobilepatient.Ahydrotherapyshowerissometimesrequired.Theseshowersusuallyconsist of multipleshower heads, sometimesasmanyas12to16,verticallymountedinordertodirectthestreamsofwateratastandingpatientbymeansofasophisticatedcontrolconsoleoperatedbyahospitalattendant.



Cystoscopic rooms Among the various plumbing fixturesrequiredincystoscopicroomsarethefollowing:wall-mountedclinicsinksequippedwithflushvalvesandbedpanwasherandcombinationfaucets;lavatoriesprovidedwithwater-supplyfit-tingsandgooseneckspouts;and,inaseparateadjacentroom,specimenwaterclosetandalavatory.Ifafloordrainisinstalledin cystoscopy, it shall contain a nonsplash, horizontal-flowflushingbowlbeneaththedrainplate.

Autopsy room The autopsy room table is usually providedwith cold and hot-water supplies, with a vacuum breaker orbackflow preventer, and a waste line. It is necessary that theplumbing designer consult with the table manufacturer andtheadministrativeauthorityregardingtherequirementsoftheautopsy room table. Drain systems for autopsy tables shall bedesignedtopositivelyavoidsplatteroroverflowontofloorsorback siphonage and for easy cleaning and trap flushing. Theautopsyroomisalsousuallyequippedwithastainlesssteelorvitreouschinasinkwithhands-freefittings,aclinicsinkanda“blood”typefloordrain.Adjacenttotheautopsyroomawaterclosetandashowerroomareusuallyprovided.Manyautopsyroomsareequippedwithwaste-disposalunitsintegralwiththesink.

Nourishment stations Thesestationsareusuallyprovidedoneachpatientroomfloornearthenursestationforservingnour-ishmentbetweenregularlyscheduledmeals.Asink,equippedforhandwashingwithhands-freecontrols,anicemaker,andahot-waterdispenser(optional)toprovideforthepatient’sser-viceandtreatmentshouldbeprovided.

Pharmacy and drug rooms Theplumbingfixturesfortheseroomsincludemedicineandsolutionsinks.Theseunitscanbecounter-typeormadeofstainlesssteelorvitreouschinawithamixingfaucetandaswingspout.Asolidsinterceptorshouldbeconsideredforcompoundingareas.

Operating-room areas Noplumbingfixturesorfloordrainsare required in the hospital’s operating room. However, thescrubbingstationlocatedadjacenttotheoperatingroomshouldhaveatleasttwoscrubsinks,usuallymadeofvitreouschinaorstainlesssteel,furnishedwithhands-freewater-supplyfittings,and equipped with gooseneck spouts. These sinks should belargeanddeepenoughtoallowscrubbingofhandsandarmstotheelbow.Asoiledworkroom,designedfortheexclusiveuseofthehospital’ssurgicalstaff,shouldbelocatedneartheoperat-ingroomarea.Thisworkroomshouldcontainavitreouschina,flushing-rim clinical sink, for the disposal of solids, with thewater-supplyfittingsconsistingofaflush-valvebedpanwasherandaseparatefaucetmountedonthewallabovethefixtureandhand-washingfacilitiesconsistingofavitreouschinaorstain-less-steel lavatory with a gooseneck spout and equipped withwrist-bladehandles.Substerileroomsshouldbeequippedwithaninstrumentsterilizerandgeneral-purposesink.Theplumbingdesignershouldconsultwiththeinstrumentsterilizermanufac-turerforanyspecialrequirementsfortheequipment.Thegen-eral-purpose sink can be countertop-mounted and equippedwithahands-freewater-supplyfittingwithagooseneckspout.

Recovery rooms Theroomsforthepost-anesthesiarecoveryofsurgicalpatientsshouldincludeahand-washingfacility,suchas a vitreous china or stainless-steel lavatory equipped with agooseneckspoutandwrist-bladehandles;andavitreouschina,flushing-rim, clinical sink for the disposal of solids, with thewater-supply fitting consisting of a flush valve and a separatefaucet mounted on the wall above the fixture with a vacuum

breaker.Abedpanwashershouldalsobe installednext to theclinicalsink.Thetypeofbedpanwasherwilldependuponthehospital’smethodofwashingandsterilizingbedpans.

Birthing rooms Eachbirthingroomshouldincludeavitreouschinalavatoryprovidedwithagooseneckspoutandwrist-bladehandles or hands-free controls. Each labor room should haveaccesstoawaterclosetandalavatory.Ashowershouldbepro-videdforthelabor-roompatients.Theshowercontrols,includ-ingpressure/thermostaticmixingvalve,shouldbelocatedout-sidethewetareaforusebythehospital’snursingstaff.Awaterclosetshouldbeaccessibletotheshowerfacility.

Anesthesia workrooms Thisareaisdesignedfortheclean-ing,testing,andstoringoftheanesthesiaequipmentandshouldcontainaworkcounter-mountedsink.Thesinkisusuallymadeofstainlesssteel.Thefaucetshouldbeofthegooseneckspoutdesignwithwrist-bladehandlesand/orhands-freecontrols.

Fracture rooms A large-size, vitreous china plaster, worksink equipped with a combination water-supply fitting andwrist-bladehandles,gooseneckspout,andplaster trapon thewasteline(locatedforconvenientaccess)shouldbeprovided.

Kitchens and LaundriesTheplumbingdesignershouldconsultwiththearchitectandthefood-service consultant for kitchen equipment utility require-ments. Typically, one of these people should provide locationand rough-in drawings for all kitchen equipment. Normallyrequired are toilet fixtures for kitchen staff, food preparationsinks,hand-washsinks,potandpan-washsinks,dishwashers,glassware washers, floor drains, hose bibbs, mixing stations,and grease interceptors. Kitchen grease traps shall be locatedand arranged to permit easy access without the necessity ofenteringfoodpreparationorstorageareas.Greasetrapsshallbeofthecapacityrequiredandshallbeaccessiblefromoutsidethebuilding without the necessity of interrupting any services. Indietaryareas,floordrainsand/orfloorsinksshallbeofatypethat can be easily cleaned by the removal of a cover. Providefloor drains or floor sinks at all “wet” equipment (such as icemachines) and as required for the wet cleaning of floors. Thelocationoffloordrainsandfloorsinksshallbecoordinatedtoavoid conditions where the location of equipment makes theremovalofcoversforcleaningdifficult.Also,thekitchenequip-mentmayrequireotherutilityservices,suchasfuelgas,steam,andcondensate.

When considering laundry facilities, the plumbing designershouldconsultwiththearchitectandthelaundryconsultantforequipment utility requirements. These facilities require large-capacity washers/extractors and dryers, presses, and foldingmachines.Waste-waterdrainagemayrequirelintintercepters.Thesefacilitiesareprimecandidatesforheatandwater-recov-ery systems. Also, the laundry equipment may require otherutilityservices,suchasfuelgas,steam,andcondensate.

The hot-water temperatures required for these areas (100,140,and180°F[38,60,and82°C])arediscussedinData Book,Volume2,Chapter6,“DomesticWater-HeatingSystems.”

Laboratory RoomsLaboratory sinks Mostofthetimearchitectsprovidethecoun-tertopsandsinks,usuallymadeofepoxyorotheracid-resistantmaterials, in their specifications. However, occasionally theplumbing designer is responsible for selecting the laboratorysinks.Laboratorysinksshouldbeacidresistantandcanbeofstainless steel, stone, or plastic. Laboratory and cup sinks are

MARCH/APRIL 2006 PlumbingSystems&Design



currently available in epoxy resin, composition stone, naturalstone, ceramic or vitreous china, polyester fiberglass, plastic,stainless steel, and lead. The lead type is not recommendedwheremercury,nitric,hydrochloricoraceticacidsareused.

Oftentheselaboratorysinksarefurnishedwiththelaboratoryequipment as rectangular sinks or cup sinks mounted in, oraspartof,countertopsandascupsinksinfumehoods.Rulesofthumbthatcanbeusedwhenthesinksizesarenotrecom-mendedbythelaboratorystaffareasfollows:1. Sinkswithacompartmentsizeof12×16×7.5in.(304.8×

406.4×190.5mm)forgenerallaboratoryworkareas.

2. Sinkswithacompartmentsizeof18×24×10in.(457.2×609.6×254mm)forclassroomworkandtests.

3. Sinkswithacompartmentsizeof24×36×12in.(609×914.4×304.8mm)forwashinglargeequipment.

Thesinkitselfandsinkoutletshouldbechemicallyresistant,aminimumof316stainlesssteel,andsodesignedthatastopperoranoverflowcanbeinsertedandremovedeasily.Theoutletshouldberemovableandhaveastrainertointerceptanymate-rialsthatmightcauseastoppageintheline.Unlessanindus-trialwatersystemisemployedthatisolatesthelaboratorywatersystemsfromthepotablewatersystem,viaacentralbackflow-preventiondevice,allfaucetsshouldbeprovidedwithvacuumbreakers.Supplyfittingsfordistilledordeionizedwaterareusu-allyeithervirginplasticortinlinedand,wherecentralsystemsare used, should be able to withstand higher pressures. Manyfittingtypes,especiallyPVC,canhandlepressuresuptobutnotexceeding50psig(344.74kPa).Inthesecases,pressureregula-tionisrequired.

Cup sinks Thesearesmall,3×6in.,3×9in.,or3×11in.(76.2× 152.4 mm, 76.2 × 228.6 mm, or 76.6 × 279.4 mm) oval sinksforreceivingchemicals,normallyfromacondensateorasupplyline.Theyaredesignedtofitintothecentersectionbetweenthetabletops;againstawall;oronraised,backledges.Thesesinksarealsocommoninfumehoods.

Laboratory glass washers are usually included, either fur-nishedbythelaboratoryequipmentsupplierorselectedbytheplumbing designer. Automatic washers are available. In addi-tiontowasteorindirectwasteservices,theseunitsrequirehotwater (usually 140°F [60°C] boosted to 180°F [82°C]) internalto the unit, distilled or deionized water, and compressed air.Manual-typeglassbottleandtubewashersmayalsoberequiredintheserooms.Tubewashersmayhavemanifold-typesupplyfittingsusingcoldwateronly.Themanifoldscanbefittedwithanumberofindividuallyserratedtipoutletsprovidedwithsepa-ratecontrolsandvacuumbreakers.

Emergency showers should be included throughout andlocatedintheadjacentcorridorsoratthedoorexits.Theshow-ersmustbeaccessible,requirenomorethan10storeach,andbewithinatraveldistanceofnogreaterthan100ft(30.5m)fromthehazardrooms.Theshowerheadisadeluge-typeshowerwitha1-in.(25.4mm)nominalcoldwater,stay-opendesign,supplyvalveoperatedbyahangingpullrod,orachainandpullring,orapullchainsecuredtothewall.Afloordrainmaybeprovided,ifrequired.Iffloordrainsareprovided,trapprimersshouldbeincorporated.

Eye and face-wash fountains are also required. These arewallorcounter-mountedunitswithafoot-pedalorwrist-blade-handle-operated, water-supply fixture; double side-mounted,fullface-washoutlets;ordeck-mounted,hand-held(withhose)

faceandbody-sprayunits.ThelatesteditionoftheANSIstan-dardforemergencyeyewashandshowerequipmentandlocalcodesshouldbeconsulted.Atemperedwatersupplyshouldbeconsidered.

Laboratory service outlets forgas,air,nitrogen,vacuum,andotherrequiredgasservicesmaybefurnishedaspartoftherelatedequipment under another contract or may be included in theplumbing work. In either case, the plumbing designer shouldbeknowledgeableaboutthevarioustypesofserviceoutletcur-rentlyavailable,thematerials(orconstruction),andtheusage(diversity).Itisdesirabletohavebodiesofcastredbrass,brassforgings,orbrassbarstockthatarespeciallydesignedforlabo-ratory use and, where possible, made by one manufacturer.Handles should be made of forged brass and provided withscrew-in-type, color-coded index discs. All outlets should beproperlylabeled.Serratedtipsshouldbemachinedfromsolidstockorforgings.Theservicefittingsshouldbechromeplatedovernickelplatingorcopperplating.Theoutletsinfumehoodsshouldhaveanacidandsolvent-resistant,plasticcoatingoverthechrome-platedsurfaceorbemadeofacid-resistantmateri-als.Nonmetallicfittingsarealsoavailable.

Special EquipmentDialysis machines Dialysismachinesrequireafunneldrainorfloorsinkandcold-waterhosebibbwithvacuumbreaker.

Heart-and-lung machines Heart-and-lung machines alsorequire a funnel-type drain. If the apparatus is located in theoperatingroom,anindirectwasteisrequired.

Electron microscopes Electronmicroscopesrequirefiltered,backflow-protected,coldwaterorcirculatedchilledwater.

Stills Stills for producing distilled water require cold waterwithavacuumbreakerandfloorsinksorfunneldrains.

Sterilizers Sterilizers require an acid-resistant floor sink orfunnel drains, a backflow-protected water supply and some-timessteamandcondensateconnections.

Film-processing equipment Film-processing (x-ray) areasrequireanacid-resistantfloorsinkorfunneldrainsforindirectwaste; and a hot, cold and/or tempered water supply operat-ingbetween40and90°F(4.4and32.2°C).Drainpipingforanyphoto-developing equipment should not be brass or copper.Polypropylene,high-silica,cast-iron,corrosion-resistantpipingand drains should be used. Silver recovery and neutralizationmayberequired;consultwiththelocalauthority.

Dental equipment Dentalareasshouldincludeconsoleser-vices(water,air,medicalgas,nitrousoxideandwaste);andfororalsurgeryaseparatesurgicalvacuumsystemshouldbepro-vided.

Theplumbingengineershouldalwaysconsultwiththeequip-ment manufacturer’s authorized representative and the localadministrativeauthority,inordertodeterminetheequipmentrequirements and the acceptability under the jurisdiction’sapplicablecodes,duringthepreliminarydesign.

DrAInAGESySTEMSForLABorATorIESInadditiontotheconventionalsanitarydrainagesystems(thosefoundinmostbuildings),specialsanitarydrainagesystemsmayberequiredinhealth-carefacilities.

Insofar as possible, drainage piping shall not be installedwithin the ceiling or exposed in operating or delivery rooms,nurseries, food-preparation centers, food-serving facilities,food-storageareas,centralservices,electronicdata-processingareas,electricclosets,andothersensitiveareas.Whereexposed,

0 PlumbingSystems&Design MARCH/APRIL 2006 PSDMAGAZINE.ORG


overheaddrainpipingintheseareasisunavoidable,specialpro-visionsshallbemadetoprotectthespacebelowfromleakage,condensation,ordustparticles.

ACID-WASTEDrAInAGESySTEMSAcid-waste drainage systems require special design criteriabecausethecorrosivesolutionsdemandspecialhandlingfromtheactualworkarea to anapprovedpoint at whichsuchacidwaste(andfumes)canbesafelyneutralizedanddischarged.Theplumbingengineermustexerciseextremecareinthisregard.

Acid-resistant waste and vent systems are necessary whereacids with a pH lower than 6.5 or alkalis with a pH greaterthan 8.5 are present. These special conditions are commonlyencountered in hospitals, research facilities, and laboratories.Sinceacidfumesareoftenmorecorrosivethantheliquidacidsthemselves,properdrainageandventingisimperative.

Nationally recognized standards for sanitary systems thathandle acid wastes and other reagents are set forth in modelplumbing codes; such systems are often further regulated bylocal building and safety or health department requirements.Forthesereasons,theplumbingengineershouldcheckforallspecialdesignconditionsthatmayaffecttheproject.

Strongacidsandcausticsmayenterthesanitary-wastesystemin large quantities and at elevated temperatures. These sub-stances can mix to form highly corrosive and even dangerouscompounds.Commonlaboratoryproceduresencourageneutral-ization or flushing with copious amounts of water in order todiluteandcoolthesechemicalstomoreacceptablelevels.How-ever,theplumbingengineermustprotecttheacid-wastesystembydesigningforthemaximumhazardconditionsthatmightbebroughtaboutbyanyhumanerror,poorhousekeeping,oracci-dentalspillage.

CorroSIvE-WASTESySTEMSMATErIALSBorosilicate glass pipe Sizesrangefrom1½to6-in.(40to150-mm) pipe. Mechanical joint, flame resistance, and clear pipeallowforeasyvisualinspectionandhighcorrosionresistance.

High-silicon cast iron Sizes range from 1½ to 4-in. (40 to100-mm)pipe.Mechanicaljoint,flameresistance,highcorro-sionresistance,firestopatfloorpenetrationequaltocastiron.More fragile and heavier than standard-weight cast iron andeasiertobreakinthefield.Excellentapplicationformoderatetohigh-budgetproject.

Polypropylene Sizesrangefrom1½to6-in.(40to150-mm)pipe. Mechanical or heat-fusion joints. Mechanical joints arenotrecommendedforstraightrunsorsizesover2in.(50mm);they should be used to access p-traps or other maintenanceareas.Flameresistantandacceptablewithinmostjurisdictions(meets 25/50 flame/smoke criteria), newer UL listed methodsareclose toglass incost.Consult localauthority forapproval.Lightweightandeasytoinstall.Goodapplicationformoderateacidsatlowtemperatures.Mustbeinstalledbyqualifiedtechni-cians. Inexpensive compared to borosilicate glass or high-sili-conecastiron.

Double-containment waste piping With ever-increasingpressuretoprotectourenvironment,double-containment(pipewithin a pipe) systems have become a consideration. Usuallymade of polypropylene inside and PVC or fiberglass outside.Systemsshouldbepitchedtowardacontainmentvaultforcol-lectionofleakingfluid.

Alarm systems canbeemployedtodetectleaksatthecollec-tion basin or, if the budget and the nature of the liquid allow,

sensorscanbeinstalledbetweenthepipewallsthatcanpinpointtheoriginalleaklocation.Thelattercouldreducetheamountofexcavationorexplorationrequiredtofindtheleak.

DISCHArGEToSEWErSMany local jurisdictions require that the building’s sanitary-sewer discharge be at an acceptable pH level before it can beadmittedintoasanitary-sewagesystem.Insuchcases,itisrec-ommendedthataclarifying(orneutralizing)tankbeaddedtothe sanitary system. Small ceramic or polypropylene clarifierswith limestone can be located under casework for low flowrates;however,sufficientspacemustbeallowedabovetheunitforservicing.Unlessproperlymaintainedandmonitored, thistypeofsystemcanberenderedineffective.Largeclarifiersandneutralizers may be regulated by the requirements of a localindustrial-wastedepartment.

ACIDIC-WASTEnEuTrALIzATIonThe lower the pH number, thehigher the concentration of acid.Discharging high concentrationsof acid into a public sewer maycause considerable corrosion topiping systems and eventual fail-ure.Mostlocalauthoritiesdonotallowacidwastestobedischargedto a public sewer without someformoftreatment.

The neutralization of acidicwastesisgenerallyandmosteco-nomically dealt with through anacid-neutralizationtank.Anacid-neutralization tank may be con-structed of polyethylene, moldedstone, stainless steel, or anotheracid-resistant material. Tanks aresizedtoprovideadwelltimeof2to3h(refertoTable2).Limestoneormarblechipsfilltheinteriorofthetank,helpingtoneutralizeincom-ingacidwastes.Chipsmaybe1to3in.(25.4to76.2mm)indiameterandshouldhaveacalciumcarbonatecontentinexcessof90%.AdischargepHsensorandroutinemaintenanceschedulemustbeprovidedtoensurethatthesystemoperatesproperly.

ACID-WASTESoLIDSInTErCEPTorAswithmanysewersystems,itisimpossibletocontrolallmate-rialsdiscardedtothedrainsystem.Unlessbuildingeffluent iscontrolled,manyunwanteditems,suchasglassfragmentsandneedles,willfindtheirway to theneutralizationtank, therebycloggingthelimestoneormarblechips.

When this happens, replacement of the chips is required.One way to prolong chip life is to install an acid-waste solidsinterceptor immediately upstream of the neutralization tank,althoughmaintenanceoftheinterceptormayhavetobedonequitefrequently.

ACID-WASTEMETErInGDETAILManylocalauthoritiesrequiresomemeansofsamplingefflu-entfromindustrial, institutional,andlaboratorybuildings.Anexampleofadeviceusedfor thispurpose isasamplingman-hole.Thisunitisinstalledasthelastcomponentbeforeneutral-

table 2 Acidic-Waste Neutralization Tank Sizing Table

Number of Lab Sinks gal (L)

2 5 (18.9)4 15 (56.8)8 30 (113.6)

16 55 (208.2)22 75 (283.9)27 90 (340.7)30 108 (408.8)40 150 (567.8)50 175 (662.4)60 200 (757.0)75 275 (1,040.9)

110 360 (1,362.6)150 500 (1,898.5)175 550 (2,081.8)200 650 (2,460.3)300 1200 (4,542)500 2000 (7,570)600 3000 (11,355)

Note: For commercial and industrial laboratories, the number of lab sinks should be multiplied by a 0.5 use factor.

MARCH/APRIL 2006 PlumbingSystems&Design 1



ized acidic wastes or treated industrial wastes are dischargedto a public sewer. There are as many types of sampling pointrequirementsastherearemunicipalsewerauthorities.Consultlocalcodeauthoritiesforindividualrequirements.

TrAPSForLABorATorySInkSThetrapisrecognizedbymostplumbingengineersastheweak-est link in theacid-wastesystem.Thetrapmustbeacidresis-tant.Ifstrongacidsandsolventscollectinanordinarytrap,fail-ureofthesystemwilloccur.Threetypesofacid-wastetrapsarecurrentlyincommonuse:p-traps,drumtraps,andcentrifugaldrumtraps.(Runningands-trapsarenotallowedbymanylocalplumbingcodesbecauseofthepotentialfortrapsiphoning.)1. P-trapsmaintainawatersealtokeeptheacidfumesfrom

reenteringtheworkarea.

2. Drum trapsprovideagreaterwatersealandarefrequentlyusedtoseparateeitherpreciousmetalsorothermatterbeforetheyenterthedrainagesystemtobecomelostorcauseastoppageinthesink.Drumtrapswithremovablebottomsshouldbeinstalledhighenoughabovethefloorforservicing.P-traps,includingsomeofthesimpledrumtraps,caneasilybeback-siphonediftheheadpressuresareextreme.

3. Centrifugal drum trapsaredesignedtopreventback-siphonageconditions.

LABorAToryWASTEAnDvEnTPIPInGSizingforunder-tablewasteandventpiping,asdeterminedbythelocalplumbingcodes,shouldbesuitablefortheinstallationand allow for future expansion. Approved corrosion-resistantpipingshouldbeusedforventpipingaswell,sinceacidfumesare also highly corrosive. Space is often limited under tablesandinventareas.Thespace-savingfeaturesofmechanicaljointpipinghaveproventobeusefulinmanyinstallations.

Note: When fusion-joint, plastic piping systems are used,mechanicaljointsshouldbeinstalledattrapsandtraparmsformaintenancereasons.

Specialisland(orloop)ventingisfrequentlyusedwhencabi-nets or work tables are located in the center of the laboratoryarea.

Thetransportatingofacidwaste,aboveandbelowtheground,mustbedoneinapproved,corrosion-resistantpiping(accept-able to the local administrative authority) and continued to asuitable point where neutralization can occur or where suffi-cientwaterorchemicalscanbeintroducedtobringthepHlevelofthesolutiontoanacceptablelevel.AcidsbelowapHof6.5normallymaynotbeadmittedintothesanitary-sewagesystemor emitted into surrounding soil, polluting (or degenerating)localgroundwater.High-siliconcastironwithhub-and-spigotjointsmaybecaulkedwithteflon,orneoprenegasketsmaybeusedforsealing.Thistypeofjointwillallowflexibilityand,whenproperlysupported,isparticularlyrecommendedonthehori-zontalrunswheretheexpansionandcontractionofpipefromheated chemicals can cause leaking. Plumbing codes requireproper bed preparation and careful backfilling on all below-groundpiping,particularlyplasticpiping.

Theplumbingengineershouldcheckthemanufacturer’srec-ommendationsinordertoevaluatetheseverityofthechemicalstobeused.Alistingofthecommonchemicalsandhowthesesubstancesreactwiththevariousmaterialsmustbeconsideredbythedesigner.

WATEr-SuPPLySySTEMSA domestic-water supply of adequate flow volume and pres-suremustbeprovidedforalltheplumbingfixturesandrelatedequipment. Systems typically encountered in these types offacilityareasfollows:1. Potable-watersystems.

A. Coldwater.B. Hotwater(atvarioustemperatures).C. Chilledwater.D. Controlled-temperature(tempered)water.E. Hotwaterrecirculation.

2. Non-potablewatersystems.

3. Pure-watersystems.

A. Distilledwater.B. Deionized(ordemineralized)water.C. Reverseosmosis.

Health-care facilities should have dual domestic-water ser-vices installed toensureprovisionofanuninterruptedsupplyof water. The design should consider water-conservation pro-visions. Many local jurisdictions have strict water-conserva-tionlawsineffect.Waterrecyclingmaybeaconsiderationforuse in landscaping,etc.,dependingon localcodeandhealth-departmentregulations.(Formoreinformation,seeData Book,Volume2,Chapter2,“Gray-WaterSystems.”)

Watersupply througha tank(suctionorgravity type)shouldbeconsideredbytheplumbingengineerwhenthewater-supplysource may be subjected to some unusual demands, pressurefluctuations,and/orinterruptionsthatwillcauseasuddenexces-sivedrawandpressurelossonthemainsystem.Thetankwillactasabuffer.Inadequateflowandpressurerequirethedesignofawater-storagetankand/oraboosterpumpforthewater-supplysystem.Excessivepressurefluctuationsarehighlyundesirableinmedical-researchlaboratories.Whensuchfacilitiesaresuppliedfromstreetpressuresystems,theengineermayprovidepressure-reducingvalvesonthebranchlines,oragravitytanksystem.

Useofdiversity factors forsizingthewatersystemsmustbecarefully analyzed by the designer. Medical-school laboratoryclassrooms have higher rates of simultaneous use than mostresearchlaboratories.Emergencyrooms,out-patienttreatmentrooms,andoperating-roomwash-upareasalsohavehighratesofsimultaneoususe.

Extremecaremustbetakeninordertoprotectthepotable-water supply from contamination (cross connection). Whenanindustrial(non-potable)systemisnotpresent,theengineershouldspecifytheappropriatetypeofvacuumbreakers(neces-saryforeachfixturebelowtherimconnection),hose-endoutlet,andanaspiratororotherserrated-tiplaboratoryoutlet,whethertheyarerequiredbythelocalplumbingregulationsornot.Thevacuum breakers provided for fume-hood outlets should belocatedoutsidethehood.Built-in(orintegral)vacuumbreakersarepreferredtothehose-endtypeunits.

PoTABLE-WATErSySTEMSColdwatershouldbeprovidedatallrequiredlocations.Thehotwater should be generated with the most economical heatingmediumavailable.

With today’s technology, several reliable methods can beapplied to produce and store domestic hot water. Refer toASPE’sDomestic Water Heating Design Manual andASPE Data Book Volume2,Chapter6,“DomesticWater-HeatingSystems,”



forin-depthexplanationsofdesignmethodsforhot-watersys-tems and a discussion of the various hot-water systems avail-able. When large “dump” loads are anticipated (kitchens andlaundries), storage of hot water is recommended. Hot-waterusageinpatient-careareasrequiresconsiderationofwatertem-peratureandbacterialgrowth.Themostcommonwater-bornebacteriumofconcernisLegionellapneumophila.

Recommended water temperatures for specific applicationsareasfollows:1. Patient-careandhospitalgeneralusagerequireswatertem-

peraturesbetween105and120°F(40.5and49°C),exceptwherethelocalplumbingcodesorotherregulationsrequireothermaximumtemperatures.Hot-waterdistributionsystemsservingpatient-careareasshallbeunderconstantrecirculationtoprovidecontinuoushotwaterateachhot-wateroutlet.Thetemperatureofhotwaterforbathingfixturesandhand-washlavatoriesshallbeappropriateforcomfortableusebutshallnotexceed120°F(49°C).

2. Kitchengeneralusagerequires140°F(60°C)tofixtures,exceptthedishwasher’ssanitizingcycle.Thesanitizingcyclerequires180to190°F(82to88°C)tothedishwasher,with180°F(82°C)minimumrequiredatthedishrack.(Consultlocalhealth-departmentregulations.)Also,somehealthdepartmentssetamaximumtemperatureof105to120°F(40.5to49°C)forhand-washinglavatories.

3. Laundryfacilitiesshouldbesuppliedwithtwowatertem-peratures,140°F(60°C)forgeneralusageand160°F(71°C)minimumtowashers/extractorsforlaundrysterilizations.

Providing a point-of-use booster heater for high-temperatureapplicationsinsteadofacentralwater-heatersystemisoftenmoreeconomical.

Aclosedsystemofchilledwatermayberequiredforthecool-ingofelectronmicroscopesandx-raytubesandshouldbeofarecirculatingdesign.

Filmprocessorsoperateatanormalrangeof40to30°F(4.4to–1.1°C).Somemodelsdorequirecontrolledwatertempera-tureforfilmprocessing.Dependingonthequalityofthewatersupply,a5to75-µfiltermayberequired.

A thermometer should also be provided on the outlets ofwaterheatersandthermostaticallycontrolledvalves.Apressureregulator,gauge,andflowmetermayalsobedesiredontheinletsideofpressure-sensitiveequipment.

non-PoTABLEWATErSySTEMSNon-potable water systems are usually employed in areashavingmultiplewaterrequirementsthatcouldcontaminatethepotable-watersupply.Areasinthiscategoryinclude:flushing-rimfloordrainsinanimalrooms,alloutletsinautopsyrooms,outletsinisolationrooms,andalloutletsininfectious-diseaseandtissue-culturerooms.Thesesystemsnormallyusereduced-pressure-typebackflowpreventersasthemeanstoprotectthepotable-water system. Hot water, when required, may be pro-vided by a separate generator supplied from the non-potablewatersystem.

PurE-WATErSySTEMS“Purewater” is thetermgenerallyusedtodescribewater thatisfreefromparticulatematters,minerals(solubleions),bacte-ria,pyrogens,organicmatters,anddissolvedgases,whichfre-quently exist in the potable water supply. Pure-water systems

areusuallyrequiredinthehospital’spharmacy,central-supplyroom,laboratories,andlaboratory-glasswarewashingfacilities.

Therearetwobasictypesofpurewateravailableinhospitalfacilities: bio-pure water (water containing no bugs or otherlife forms)andhigh-puritywater (purewater that is free fromminerals,dissolvedgases,andmostparticulatematters).RefertoASPE Data Book,Volume2, Chapter11,“WaterTreatment,Conditioning, and Purification,” for additional information onwaterpurity.

Waterpurityismosteasilymeasuredasspecificresistance(inohm-centimeter [Ω-cm] units) or expressed as parts per mil-lion(ppm)ofanionizedsalt(NaCl).Thetheoreticalmaximumspecificresistanceofthepurewaterisgivenas18.3MΩ-cmat77°F(25°C).Thiswaterpurityisdifficulttoproduce,store,anddistribute.Thiswateris“starved”forimpuritiesandconstantlyattempts to absorb contaminants. It is important to note thatthespecificresistanceofthepurewaterisindicativeonlyofitsmineral contents and in no way shows the level of bacterial,pyrogenic, or organic contamination. An independent labora-toryanalysisshouldbemade,wheneverpossible.

Thefivebasicmethodsofproducingpurewaterareasfollows:distillation, demineralization, reverse osmosis, filtration, andrecirculation.Dependinguponthetypeofpurewaterrequiredinthefacility,one(ormore)ofthesemethodswillbeneeded.Under certain conditions, a combination of several methodsmaybenecessary.1. Distillation producesbio-purewater,whichiscompletely

freefromparticulatematters,minerals,organics,bacte-ria,pyrogens,andmostofthedissolvedgasesandhasaminimumspecificresistanceof300,000Ω.Animportantconsiderationinthiscaseisthatthewaterisfreefrombac-teriaandpyrogencontamination,whichisdangeroustothepatients,particularlywhereintravenoussolutionsareconcerned.Bio-purewaterisneededinthehospital’sphar-macy,central-supplyroom,andotherareaswheretheremaybepatientcontact.Bio-purewatermayalsobedesiredincertainspecificlaboratoriesattheowner’srequestandasafinalrinseinthelaboratory’sglasswarewasher.

Thetypicalwater-distillationapparatusconsistsofanevaporatorsection,aninternalbafflesystem,awater-cooledcondenser,andastoragetank.Thebestmaterialforitsconstructionisapureblock-tincoatingforboththestillandthetank.Theheatsources,inorderofpreferencebasedoneconomyandmaintenance,areasfollows:steam,gas,andelectricity.Thestillmaybeoperatedmanuallyorauto-matically.Thedistilledwatermaybedistributedfromthestoragetankbygravityorbyapump.Adrainisrequiredforsystemdrainageandflushing.Onstillslargerthan50gph(189.3L/h),acoolingtowershouldbeconsideredforthecondenserwater.

2. Demineralization, sometimescalled“deionization,”pro-duceshigh-puritywaterthatiscompletelyfreefromminer-als,mostparticulatematters,anddissolvedgases.Depend-ingupontheequipmentused,itcanhaveaspecificresis-tancerangingfrom50,000Ωtonearly18MΩ.However,itcouldbecontaminatedwithbacteria,pyrogens,andorgan-ics(thesecontaminantsmaybeproducedinsidethedemin-eralizeritself).Demineralizedwatercanbeemployedin




mostlaboratories,thelaboratory’sglass-washingfacilities(asafinalrinse)andasthepre-treatmentforstillfeedwater.

Thetypicaldemineralizerapparatusconsistsofeitheratwo-beddeionizingunit(witharesistivityrangeof50,000Ωto1MΩ)oramixed-beddeionizingunit(witharesistivityrangeof1to18MΩ).Thecolumnsareofaninertmaterialfilledwithasyntheticresin,whichremovesthemineralsbyanionizationprocess.Sincetheunitoperatesonpressure,astoragetankisnotrequiredorrecommended(asbacteriawillgrowinit).Ademineralizermustbechemi-callyregeneratedperiodically,andduringthatregenerationtimenopurewaterisproduced.Ifacontinuoussupplyofpurewaterisneeded,abackupunitshouldbeconsideredbytheengineer,astheregenerationprocesstakesseveralhours.Theregenerationprocesscanbedonemanuallyorautomatically.Anatmospheric,chemical-resistantdrainisrequired.High-flowwaterisrequiredforbackwashduringtheregeneration.

3. Reverse osmosis (RO) producesahigh-puritywaterthatdoesnothavethehighresistivityofdemineralizedwaterandisnotbio-pure.UndercertainconditionsanROprocesscanoffereconomicadvantagesoverdemineralizedwater.Inareasthathavehighmineralcontents,anROprocesscanbeusedasapre-treatmentforademineralizerorstill.

Thereareseveraltypesofreverseosmosisunitscurrentlyavailable.Unitsconsistofasemipermeablemembrane,ineitherarollformoratubecontainingnumeroushollowfibers.Thewateristhenforcedthroughthesemipermeablemembraneunderhighpressure.Adrainisrequiredwiththesesystems.

Note:Chlorinemustberemovedfromthewater,otherwiseitwilldestroytheROmembrane.

4. Filtration Varioustypesoffilterarecurrentlyavailabletoremovetheparticulatemattersfromthewaterasapre-treatment.Dependinguponthetypeoffilter,adrainmayberequired.Bacteriamaybeeliminatedthroughultravioletsterilization.

5. Recirculation High-puritysystemsshouldbeprovidedwithacirculationloop.Dead-endlegsshouldbeavoidedwheneverpossibleorlimitedto50in.(1.52m). Systemdesignvelocityshouldbebetween4and7fps(1.22and2.13m/s)soastodiscouragebacteriaaccumulationandprovidetransportbacktoanultravioletsterilizerandfiltrationforremoval.

Pure-water piping system materials Water-treatmentsystemcomponentsareselectedtoremovevariousimpuritiesfromtheinfluentwater.Connectingvarioussystemcomponentstogetherinvolvestheuseofinterconnectingpiping.Theuseofthispipingshouldnotcontributetoaddinganysuchimpuritybackintothetreatedwater.

Selection of piping-system materials is determined by theapplication intended, the availability of the material, and thecostofthematerial.Pure-waterapplications,suchasexistinthehealth-careindustry,canbeverysensitivetothepipingmeth-odsselected.

Generalpure-waterpipingrequirementsinclude:1. Inertmaterials—mustnotleachcontaminationintowater.

2. Cleanjoiningmethods—avoidsolvents,lubricants,andcrevices.

3. Nomaterialerosion—mustnotflakeoffparticles.

4. Materialshouldnotenhancemicroorganismgrowth.

5. Materialshouldbesmooth,crackandcrevice-free,andnonporous.

6. Avoiddeadlegs—systemshouldhavecontinuousflowthroughpiping.

7. Providechemicalcleaningconnections.

8. Install(slope)withfuturecleaninganddisinfectioninmind.

Awidevarietyofpipingmaterialsareavailableonthemarkettoday.Theirpropertiesandcostcoverawiderange.Common pure-water materials1. Stainlesssteel—variousgrades(304L&316L).

2. Aluminum.

3. Tin-linedcopper.

4. Glassorglass-linedpipe.

5. PVC/CPVC—Polyvinylchloride/chlorinatedpolyvinylchlo-ride.

6. Polypropylene.

7. Polyethylene.

8. ABS—Acrylonitrilebutadienestyrene.

9. PVDF—Polyvinylidenefluoride.

Metal pipe Aluminum, tin-lined copper, and stainless-steelpipehaveallbeenusedinpure-watertreatmentsystems.Tin-linedpipewasoncethematerialofchoiceinultra-purewatersystems.However,itdoesleachtinandeventuallycopperintothe process fluid. Methods of joining tin-lined pipe can alsoleavenon-smoothjointswithcrevices.

Aluminum pipe has also been used in pure-water systems.Purewatercreatesanoxidelayerinsidethepipethatcontinu-allyerodes,producingparticlesandaluminuminthewater.

Stainlesssteelhasbeenusedextensivelyinhigh-puritywatersystems.Itcanbejoinedwiththreads,buttwelded,flanged,ormanufactured with sanitary-type connection ends. Becauseitcanusesanitaryjointsandcanhandlesteamsterilizing,thesanitary-typeconnectionmethodhasbeenusedinmanyphar-maceutical applications. However, experience has shown thateventhebestgradesofstainlesssteel,withthebestjoints,stillleachmaterialfromthemetalthatcancauseproblemsincriti-calwatersystems.

Glass or glass-lined pipe Glasspipinghasbeenusedinsomespecial laboratory applications but, because it is fragile anddoesleachmaterialintothewater,itisnotgenerallyconsideredapplicableforhigh-puritywatersystems.

PVC PVC pipe has been used on equipment and in pipingsystems successfully for many years. Advances in technology,especially inelectronics,havenowraisedquestionsabout the“truepurity”orinertnessofPVC.

PVC pipe contains color pigments, plasticizers, stabilizers,andantioxidantsthatcanallleachoutoftheplasticandintoultra-purewater.Rememberthat18,000,000-Ωqualitywaterishighlyaggressive.WhenPVCpipeismade(extruded),bubblesofairexist,someofwhicharecoveredoverwithathinfilmofPVContheinteriorwallsofthepipe.Asthepipeages,thesethincoveringswearaway,exposingsmallholeswhichthenserveas



debris-collecting or microorganism-breeding sites, not to men-tion the contribution of PVC particles and the potential release of organic dispersants, stabilizers, etc., originally trapped in these bubbles (holes).

Joints, either solvent welded or threaded, can leave crevices for the accumulation of particles and bacteria. Solvents from the weld can also leach into the water.

Premium grades of PVC, which reportedly have fewer leach-ables than standard PVC, are now being marketed.

CPVC is a special high-temperature PVC that has similar ero-sion and leachable characteristics.

Polypropylene Polypropylene is a very inert, strong piping material. However, in the manufacture of the pipe antioxidants and other additives are used to control embrittlement. These additives are potential sources of contaminants that can leach into the water. However, a virgin material with no leachable products is now available.

Polypropylene pipe shows good ability to withstand both cor-rosive chemicals and high temperatures, up to 220°F (104°C). The natural toughness of the material minimizes damage to pipe during installation and service.

Polypropylene is generally joined by the butt-fusion method, resulting in smooth joints.

ABS Acrylonitrile butadiene styrene (ABS) plastic pipe has been used in the primary stages of water-treatment systems because of relatively low cost and ease of installation.

ABS has some of the same contamination leach problems as PVC. In its manufacture, pigment dispersants, surfactants, sty-rene, and other additives are used that can leach into water over time. Hydrogen peroxide (used for system cleaning) will also attack ABS plastic.

PVDF There are numerous types of high-molecular-weight fluorocarbon pipes on the market, SYGEF, KYNAR, and HALAR, to name a few. Polyvinylidene fluoride (PVDF) plastic can be extruded without the use of additives that can leach out later. The different polymerization techniques used by each manu-facturer can produce slightly different properties.

PVDF pipe is currently considered to be the state of the art in pure-water piping systems. It has exceptional chemical resis-tance; temperature range, –40 to 320°F (–40 to 160°C); impact strength; resistance to UV degradation; abrasion resistance; and smooth, clean, inside surfaces that discourage the collection of bacteria and particles. Most laboratory test reports show virtu-ally zero leachables from PVDF piping systems.

PVDF pipe is joined by the butt-fusion method, resulting in clean, smooth joints.

When system pressures exceed 70 psig (482.6 kPa) or tem-peratures exceed 75°F (24°C), plastic piping system manufac-turers should be consulted for compatibility. Polypropylene or PVDF-lined metal piping systems may be incorporated to meet pressures up to 150 psig (1034.2 kPa).



ConTInuInG EDuCaTIon

1. high-silicon cast iron pipe is _________ than standard weight cast iron pipe.a. lighterb. heavierc. more costlyd. less costly

. Fixture-unit values for unique fixtures found in health-care facilities can be _________.a. estimatedb. assigned by the authority having jurisdictionc. higher then anticipatedd. found in Table 2-2

. The theoretical maximum specific resistance of pure water is _________ ohm-centimeter units at oF.a. 12.6b. 16.8c. 18.3d. 20.2

. hand washing lavatories are not required in _______.a. family waiting roomsb. janitor’s closetsc. outpatient services areasd. nurses’ stations

. a review of applicable code requirements is ________.a. always requiredb. is under the jurisdiction of the Joint Commission of

the Accreditation of Hospital Organization (JCAHO)c. restricted to local codes onlyd. is not necessary for the experienced plumbing

engineer

. when referring to acid waste, the lower the ph number, the _________ the concentration of acid.a. lowerb. higherc. more neutrald. none of the above

. It is common for architects to locate the piping shafts and the spaces in direct conflict with the structural framing because _________.a. they do not know any betterb. it serves their purposec. the plumbing designer has not given the architect

direction regarding space requirementsd. none of the above

. what type of vent system is used on laboratory sinks that are located in the center of laboratory areas? a. end ventb. stack ventsc. loop ventsd. crown vents

. what is the size, in liters, of an acid waste neutralization tank that serves laboratory sinks?a. 1,020.9 b. 1,040.9 c. 1,050.9d. 1,060.9

10. This chapter discusses _________.a. the requirements of health care facilitiesb. the provisions that may be encountered by the

plumbing professional in the design of a health care facility

c. nursing homes, medical schools, and medical laboratories

d. energy codes as they apply to medical facilities

11. x-ray areas require _________.a. tempered waterb. corrosion-resistant piping and drainsc. silver recoveryd. a and b

1. which of the following piping materials is not commonly used for the distribution of pure water?a. aluminumb. CPVCc. copperd. PVDF

Doyoufinditdifficulttoobtaincontinuingeducationunits(CEUs)?Is it hard for you to attend technical seminars? Through PlumbingSystems&Design(PS&D),ASPEcanhelpyouaccumulatetheCEUsrequired formaintainingyourCertified inPlumbingDesign(CPD)status.

ASPEfeaturesatechnicalarticleineveryissueofPS&D,excerptedfrom its own publications. Each article is followed by a multiple-choicetestandasimplereportingform.

Readingthearticleandcompletingtheformwillallowyoutoapplyto ASPE for CEU credit. For most people, this process will requireapproximately1hour.Anominalprocessingfeeischarged—$25forASPE members and $35 for nonmembers (until further notice, thememberfeeiswaived).Ifyouearnagradeof90%orhigheronthetest,youwillbenotifiedthatyouhavelogged0.1CEU,whichcanbe

appliedtowardtheCPDrenewalrequirementornumerousregula-tory-agencyCEprograms.(Pleasenotethatitisyourresponsibilitytodeterminetheacceptancepolicyofaparticularagency.)CEUinfor-mationwillbekeptonfileattheASPEofficefor3years.

Nocertificateswillbeissuedinadditiontothenotificationletter.You can apply for CEU credit on any technical article that hasappearedinPS&Dwithinthepast12months.However,CEUcreditonlycanbeobtainedonatotalofeightPS&Darticlesina12-monthperiod.

Note:IndeterminingyouranswerstotheCEquestions,useonlythe material presented in the continuing education article. Usingotherinformationmayresultinawronganswer.


CE Questions—“Plumbing Design for Health Care Facilities” (PSD 132)



Plumbing Systems & DesignContinuing Education application Form

1. Make a photocopy of this form. Leaving this page in PS&D allows others to use it to obtain continuing education units (CEUs).2. PRINT your name and address. Be sure to place your membership number in the appropriate space. This form is valid up to

1 year from date of publication. The PS&D continuing education unit program is approved by ASPE for up to 1 contact hour (0.1 CEU) of credit per article studied.

3. Answer the multiple-choice continuing education (CE) questions (found after each CE article) and the appraisal questions on this page.

4. Submit this form and the answer sheet below, with the payment of the appropriate fee by check or money order made pay-able to ASPE, or submit the credit card information to ASPE Education Credit, 8614 W. Catalpa Avenue, Suite 1007, Chicago, IL 60656–1116.

5. Participants who earn a passing score (90%) on the CE questions will receive a letter of certification within 30 days of PS&D’s receipt of the application (no special certificates will be issued). (CEU information will be retained on the ASPE Database.) Participants who wish to retake the test should submit their retest along with an additional fee—$25 for an ASPE member (currently waived) or $35 for a nonmember.


Name __________________________________________________________________________________________________


Organization ____________________________________________________________________________________________

Billing Address ___________________________________________________________________________________________


Country ___________________________________________ E-mail ________________________________________________


PS&D Continuing Education answer SheetPlumbing Design for Health Care Facilities (PsD 132)Questions appear on page 66. Circle the answer to each question.

q 1. a B C Dq . a B C Dq . a B C Dq . a B C Dq . a B C Dq . a B C Dq . a B C Dq . a B C Dq . a B C Dq 10. a B C Dq 11. a B C Dq 1. a B C D

appraisal questionsPlumbing Design for Health Care Facilities (PsD 132)






Signature

Expiration date: Continuing education credit will be givenfor this examination through March 1, 00.Applications received after that date will not be processed.








PSD

141

Irrigation Systems


SEPTEMBER 2007

PSDMAGAZINE.ORG


IntroductIonThe function of an automatic irrigation system is to provide and distribute a pre-determined amount of water to economi-cally produce and maintain ornamental shrubs, cultivated lawns, and other large turf areas. Other benefits of an automatic irrigation system include convenience, full landscape coverage, easy control for overnight and early morning watering, and minimized plant loss during drought. This chapter discusses the basic design criteria and components of irrigation systems for ornamental lawns and turf. Among the factors considered are water quality and requirements, soil consid-erations, system concepts, and system components. A design information sheet is also provided, as Appendix A, to assist the plumbing engineer in the orderly col-lection of the required field information and other pertinent data.

Water QualIty and reQuIrementsIn urban areas, where the source of the water supply is often the municipal water system, the plumbing engineer does not need to be concerned with the qual-ity of the water. In cases where private sources are used and the water quality is unknown, the water should be analyzed by the appropriate local health authority having jurisdiction prior to use. The three main areas of concern are as follows:1. Any silt content that, if high, may

result in the baking and sealing of soils

2. Any industrial waste that may be harmful to good growth

3. Any soluble salts that may build up in the root area

The most common solution currently available for handling excessive amounts of silt is the construction of a settling basin, usually in the form of a decorative lake or pond. In those areas where the salt

content is excessive, 1,000 parts per mil-lion (ppm) and above, the inability of the soil to cope with the problem may require the use of special highly salt-tolerant grasses.

The quantity of water required for an effective irrigation system is a function of the type of grass, the soil, and local weather conditions. The quantity of water is usually expressed as the depth of the water applied during a given period over the area to be covered. The amount of water applied to a given area can be con-trolled easily by adjusting the irrigation system’s length and frequency of opera-

Irrigation Systems

Reprinted from ASPE Data Book Volume 3: Special Plumbing Systems, Chapter 4: “Irrigation Systems.” © American Society of Plumbing Engineers.

Table 1 Net Amount of Water to Apply per Irrigation Cycle

Soil Profile Amount, in. (mm)Coarse, sandy soils 0.45 (11.43)Fine, sandy loams 0.85 (21.59)Silt loams 1.10 (27.94)Heavy clay or clay loams 0.90 (22.86)

Note: Net amount of moisture required based on 12 in. (304.8 mm) root depth.

Figure 1 Examples of a Block System

2 Plumbing Systems & Design SEPTEMBER 2007 PSDMAGAZINE.ORG



tion. An efficient irrigation system takes into consideration the rate of the appli-cation of the water, usually expressed in inches per hour, and the attempt to match the application rate with the absorption rate of the soil. Often, this condition is achieved through frequent short water-ing cycles.

soIl consIderatIonsSandy, porous soils have relatively high

absorption rates and can handle the high output of the sprinklers. Steep slopes and very tight, nonporous soils require low precipitation rates to avoid erosion damage and wasteful runoff.

A sufficient amount of water must be applied during each irrigation period to ensure penetration to the root zone. Table 1 suggests guidelines for several soil pro-files (net amount of water to apply per irrigation cycle). In the absence of any specific information on the soil and local weather conditions, the irrigation system may be designed for 1½ inches (38.1 mil-limeters) of water per week. The plumb-ing engineer should consult with the local administrative authority to determine compliance with the applicable codes in the jurisdiction. The engineer can obtain specific information on the soil and local weather conditions by contacting a local weather bureau, university, or state engi-neer.

system conceptsThe three basic system concepts that can be used by the engineer in the design of an irrigation network are the block method, the quick-coupling method, and the valve-per-sprinkler method.

The block system is an approach in which a single valve controls the flow of water to several sprinklers. It is ideal for residential and other small turf areas. Either manual or automatic valves may be used in the block system. As the irriga-tion area increases or where high-volume sprinklers are employed, the block system becomes less attractive to the engineer because of the large valves and pipelines required. Examples of the block system are shown in Figure 1.

The quick-coupling irrigation system is an answer to the high cost incurred on large block system projects. Development of the quick-coupling valve provided a more flexible irrigation system. The valve is located underground but can be acti-vated from the surface. Where manpower is not critical and security is reasonable, the quick-coupling irrigation system may

be considered by the engineer. An exam-ple of a quick-coupling valve is illustrated in Figure 2.

The last concept in sprinkler system design is the valve-per-sprinkler method. Small actuator valves, operated at low volt-age, provide great flexibil-ity and control. Sprinklers in diverse areas having the same (or similar) water requirements may be operated concurrently. In other applications, such as quarter applications cov-ering quarter circles or half circles, the irrigation sprin-klers may be piped, wired, and operated together through system program-mers. The valve-per-sprin-kler system provides the opportunity to standardize the pipe sizes by selecting the appropriate sprinklers

to be operated at any given time. Figure 3 illustrates this design.

system components

sprInklersOne of the most important considerations for the plumbing engineer when design-ing an irrigation system is the selection of the sprinklers. Sprinklers are mechanical devices with nozzles used to distribute water by converting water pressure to a high-velocity discharge stream. Many different types of sprinklers are manufac-tured for a variety of system applications. The plumbing engineer should become knowledgeable of the various types before selecting the sprinklers, as the flow rates and operating pressures must be nearly the same in each of the irrigation system’s circuits.

Spray Sprinklers Surface-type spray and pop-up spray sprinklers (see Figure 4) produce a single sheet of water and cover a relatively small area, about 10 to 20 feet (3.05 to 6.10 meters) in radius. These sprinklers can operate on a low-pressure range of 15 to 35 pounds per square inch (psi) (103.4 to 241.3 kPa). They apply the water at a high rate of application—1 to 2 inches/hour (25.4 to 50.8 mm/hour)—and are most economical in small turf or shrub areas and in irregularly shaped areas.

Due to the fine spray design, the pattern can be easily distorted by the wind; there-

Figure 2 Quick-Coupling Valve

Figure 3 Valve-in-Head System

SEPTEMBER 2007 Plumbing Systems & Design 3


fore, these sprinklers should be installed in protected areas.

Impact Sprinklers Impact sprinklers (see Figure 5) can be permanent or mov-able and either the riser-mounted type (see Figure 2) or the pop-up rotary type (see Figure 6).

Impact sprinklers have an adjustable, revolving water stream and are available

in both single-nozzle and double-nozzle designs. These devices can oper-ate at a higher pressure (25 to 100 psi [172.3 to 689.5 kPa]) and cover larger areas (40 to 100 feet [12.2 to 30.5 meters] in radius). The water is applied at a lower rate (0.20 to 0.5 inches/hour [5.08 to 12.7 mm/hour]). Because of its larger, more compact stream of water, this sprinkler is not easily distorted by the wind and is most economical in large, open turf areas.

Freestanding sprin-klers are not desirable where they are exposed. In such cases, the pop-up, rotary-type sprinklers shown in Figure 6 may be used. These nozzles rise above the ground level only when the water is being delivered to the unit.

Half-circle, rotary sprinklers can discharge the same volume of water as full-circle units. A half-circle, rotary sprinkler can provide the same amount of water as a full-circle unit over half the area, doubling the application rate. Quarter-circle sprinklers will quadruple the appli-cation rate. Some equip-ment manufacturers use different nozzles to com-pensate for the reduced area and to provide a uniform application rate. If compensating nozzles are not used in half-circle sprinklers, these units must be valved and

operated separately for a balanced appli-cation of the water.

Shrub Sprinklers Several types of shrub sprinklers are available, including bubblers (see Figure 7), flat-spray sprin-klers, and stream-spray sprinklers. Shrub sprinklers can be mounted on risers to spray over plants. If the plants are tall and not dense near the ground, shrub

sprinklers can be used on short risers, and the spray can be directed under the plants. The spray can also be kept below the plant. Flat-spray shrub heads are best employed for these applications.

Trickle Irrigation Trickle irrigation is commonly used in vineyards and orchards and routed through tubing with special emitters installed at each planting. Most emitters have flexible orifices and may have provisions for adding fertilizer. These irrigation systems have a low-vol-ume usage and usually are not installed in conjunction with conventional lawn sprinkler systems.

ValVesRemote-control valves are generally clas-sified into three basic categories: electric, hydraulic, and thermal-hydraulic. The electrically operated valve receives an electric signal from the controller and actuates a solenoid in the valve. This sole-noid opens and closes the control valve. The hydraulic control valve is operated with the water pressure and has control tubing from the controller to the valve. The thermal-hydraulic control valve uses an electric signal from the controller to heat up the components of the valve to open the unit. The most common use of this valve is to control the water usage to the different zones.

These devices should be installed with access for maintenance. Most control valves have some provisions for manual operation. In some systems, manual con-trol valves are installed in pits or vaults

Figure 4 Pop-Up Spray Heads

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Figure 5 Impact Sprinkler

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Figure 6 Rotor Sprinkler—Arcs and Full Circles

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CONTINUING EDUCATION: Irrigation Systems


with a long T-handle wrench used for the activation of each circuit.

An irrigation system may be installed with an automatic check valve on the sprinkler heads. When a zone is installed on sloping terrain, these valves will close when they sense a low pressure at turn-off, preventing the drainage of the supply pipe through a sprinkler head installed in a lower area.

Atmospheric vacuum breakers (see Figure 8) must be installed on every sprinkler circuit downstream of the con-trol valve to eliminate the possibility of back-siphonage into the potable water system. Many (if not all) local jurisdic-tions have codes that require this type of valve. The plumbing designer should consult with the local administrative authority and check all applicable codes for their requirements.

Pressure-reducing valves are installed where higher street pressures are involved and also are commonly used to maintain a constant pressure where the inlet pres-sures may vary. Some manufacturers offer remote-control valves with pressure regulation.

Low-flow control valves may be installed to avoid damage to the piping or tubing from pressure surges during the filling of a (dry) system. This control valve allows a slow filling of the piping or tubing until the pressure is established.

In climates where freezing conditions may occur, automatic-type drain valves should be installed at the low points of the system to allow for drainage of the system. This control valve will open auto-matically when the water pressure drops below a set point. In heavy or dense soils, a pit of gravel should be provided for quick drainage.

BackfloW deVIcesAn irrigation system may be installed with an automatic check valve on the sprin-klers. When a zone is installed on sloping terrain, these valves will close when they sense a low pressure at turnoff, prevent-

ing drainage of the supply pipe through a sprinkler head installed in a low area.

The use of pressure vacuum break-ers to eliminate the possibility of back-siphonage into the potable water system is the minimum level of backflow pre-vention accepted by most jurisdictions. The plumbing engineer should consult with the local administrative authority and check all applicable codes for their requirements.

controllersPresently, many types of controllers for irrigation systems are available. Selec-tion of this device is based on the spe-cific application involved. Controllers are programmed to activate each irriga-tion zone at a specific time and also will control the length of time that each zone is activated. Some controllers have a cal-endar that allows the irrigation system to be used only on certain days. Other types of controllers have manual (or automatic) overrides to shut down all systems during rain or to turn on specific zones for extra water. Some controllers have soil mois-ture monitors, which turn on zones only when needed. Controller panels can be

surface mounted, recessed mounted, or pedestal mounted. Figure 9 shows a typi-cal illustration of a surface-mounted and a pedestal-mounted irrigation system programmer.

desIgn InformatIonWhen designing an underground sprin-kler system, the plumbing engineer should consider the following factors: the site plan, type of plants, type of soil, type and source of water, and system location.

sIte planAn accurate site plan, preferably laid out to scale and showing all buildings, shrubs, trees, hedges, walks, drives, and parking, should be drawn as accurately as possible. Areas where overspray is unde-sirable, such as walkways and buildings, should be clearly noted. Property lines also should be shown on the site plan. The heights and diameters of shrubs and hedges should be indicated.

types of plantIngsThe engineer should show the areas that will be irrigated on the site plan as well as the areas that will be omitted. Those areas that require a different style of sprinkler and separate zoning also should be indi-cated. Some plantings require more fre-quent watering than others; therefore, they will require a separate zone and control valve. The engineer should deter-mine whether the plantings allow spray on their leaves (or any other special type of spray) and should select the sprinklers accordingly.

Figure 8 Installation of Atmospheric-Type Vacuum Breakers

Figure 7 Nozzles—Adjustable Arcs and Patterns

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type of soIlThe type of soil determines the proper rate of application of water to the soil. The length and frequency of the applications can be determined by considering the soil and the types of plants.

A sufficient amount of water must be applied during each irrigation period to ensure penetration to the root zone. Table 1 recommends acceptable guidelines for several types of soil profiles. Where avail-able, the engineer should secure local soil and weather conditions by contacting the local state extension engineer, a uni-versity, or the weather bureau. The local weather bureau usually publishes an evapotranspiration guide, which shows the deficit water required to maintain turf grass. This value is compiled by measuring the rainfall minus the evaporation taking place during a particular period. The bal-ance is the amount of water required. In the absence of any specific information on local soil and weather conditions, the irrigation system should be designed for

a minimum of 1½ inches (38.1 mm) of water per week.

Sandy, porous soils (as previously indi-cated) have relatively high absorption rates and can handle the high output of sprinklers. Steep slopes and very tight, nonporous soils require low precipita-tion rates to avoid erosion damage and runoffs.

type and source of WaterThe source of the water should be located on the site plan. If the water source is a well, the pump capacity, well depth, pump discharge pressure, and other pertinent data should also be recorded. If the water source is a city water main, the locations, size, service-line material, and length of piping from the service line to the meter should be researched by the plumbing engineer. The water meter size and the static water pressure of the city main are also needed. The engineer should determine whether special meter pits or piping arrangements are required by the utility company.

system locatIonDue to the influence of physical and

local climatic conditions, the general area may require specific design consid-erations, such as drain valves on systems subjected to freezing temperatures. Windy areas require closer spacing of sprinklers, and the wind velocity and direction must be considered. For areas on sloping ter-rain, there will be a difference in the outlet pressure, and consideration must be made for system drainage.

The engineer must review local codes to determine acceptable piping materi-als, installation, requirements, and the approved connection to municipal water works.

referencesThe ABCs of Lawn Sprinkler Systems. Irri-

gation Association, Fairfax, Virginia.Pair, Claude H., ed. Sprinkler Irrigation,

4th edition. Sprinkler Irrigation Association, Silver Spring, Maryland.

Architect-engineers Turf Sprinkler Manual. The Rainbird Company, Glendora, California.

Design Information for Large Turf Irriga-tion Systems. The Toro Company, Riverside, California.

Young, Virgil E. Sprinkler Irrigation Systems. Mister Rain, Inc., Auburn, Washington.

resourcesThe Irrigation Association, www.irriga-

tion.org

Figure 9 Irrigation Sprinkler Programmers

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CONTINUING EDUCATION: Irrigation Systems


appendIx a

suggested InformatIon sheet for sprInkler system desIgnAll available information should be contained on this sheet, plot plan, or both.

1. Project name_______________________________ Address_______________________________________2. Water supply:

a. Location and size of existing tap, meter, pump, or other __________________________________

b. Existing meter, pump, or tap capacity: Residual pressure _______________GPM _____________

c. Power supply: Location _________________________________________ Voltage _________________

d. Length, type, location, and size of existing supply line (identify on plan)

3. Area to be watered. Identify all planted areas whether shrubbery or trees; indicate clearance under trees. (Identify on plan.)4. Soil type: Light _______________________ Medium _____________________ Heavy __________________5. Hours per day and night allowed for irrigation __________________________________________________6. Amount of precipitation required per week __________________________________________________7. Area to be bordered or not watered (identify on plan)8. Elevations and prevailing wind conditions (identify on plan)9. Type of system: (a) Automatic electric _________________ (b) Automatic hydraulic _______________ (c) Manual pop-up ______________ (d) Manual quick-coupling _____________ (e) Other____________10. Indicate equipment preference _____________________________________________________________11. Indicate preferred location for valves and controllers _________________________________________________________________

______________________________________________________________12. Indicate vacuum breaker and/or drain valve requirement ____________________________________________________________

_________________________________________________________________13. Indicate pipe material preference: 2½” and larger ______________ 2” and smaller _______________14. Indicate any preference for sprinkler riser types ____________________________________________

SPECIAL NOTES (use additional sheet if necessary) _____________________________________________________________________

____________________________________________________________________________________________________________________

____________________________________________________________________________________________________________________

____________________________________________________________________________________________________________________



About This Issue’s ArticleThe September 2007 continuing education article is “Irrigation Systems,” Chapter 4 of ASPE Data Book 3: Special Plumbing Systems.

This chapter discusses the basic design criteria and com-ponents of irrigation systems for ornamental lawns and turf. Among the factors considered are water quality and requirements, soil considerations, systems concepts, and components. A design information sheet is also provided, as Appendix A, to assist the plumbing engineer in the orderly collection of the required field information and other perti-nent data.


PSD

141


CE Questions—“Irrigation Systems” (PSD 141)1. The function of an irrigation system is _________.

a. to conserve waterb. as a labor-saving device for yard maintenancec. to provide and distribute a predetermined amount of

water to economically produce and/or maintain shrubs, lawns, and turf

d. none of the above

2. When designing an underground sprinkler system, the plumbing engineer should consider which of the following factors?a. site plan, b. types of plants, c. type of soil,

d. all of the above

3. The amount of water to apply per irrigation cycle in coarse, sandy soil, assuming a 14-inch root depth, is ____.a. 0.45 inch, b. 0.85 inch, c. 1.10 inches,

d. none of the above

4. The three basic concepts that can be used by the engineer in the design of the irrigation network are _________.a. block method, quick-coupling method, and valve-per-

sprinkler methodb. uniform water coverage, controlled depth of water per

square foot, and zone control methodc. both a and bd. none of the above

5. Water for irrigation systems _________.a. may be from an urban sourceb. may be from a private sourcec. may be from a storage reservoir, tank, or surface pondd. any of the above

6. Soil conditions _________.a. need not be considered when urban sources of water are

usedb. affect the amount of water neededc. are not important because the landscaper will supply the

proper soil for the plants usedd. should have high absorption rates

7. The last concept in sprinkler system design is _________.a. plant type, b. soil type, c. the valve-in-head method,

d. slope of grade at the site

8. One of the most important considerations for the plumbing engineer when designing an underground sprinkler system is _________.a. the selection of the sprinkler headsb. the system controllerc. using a sufficient quantity of waterd. using the least amount of water

9. Windy areas require _________.a. more water due to evaporationb. closer spacing of sprinklers c. increased outlet pressured. both a and c

10. Atmospheric vacuum breakers must be installed _________.a. only if required by codeb. on every sprinkler circuit downstream of the control

valvec. when the designer does not want to use a backflow

preventerd. below grade

11. Trickle irrigation is commonly used in _________.a. vineyards and orchardsb. where water is scarcec. foreign countriesd. less affluent areas

12. In climates where freezing conditions may occur, _________.a. manual drain valves should be installedb. reduced-pressure backflow preventers should not be

installedc. automatic-type drain valves should be installedd. the piping system must be heat traced







Plumbing Systems & Design Continuing Education Application FormThis form is valid up to one year from date of publication. The PS&D Continuing Education program is approved by ASPE for up to one contact hour (0.1 CEU) of credit per article. Participants who earn a passing score (90 percent) on the CE questions will receive a letter or certification within 30 days of ASPE’s receipt of the application form. (No special certificates will be issued.) Par-ticipants who fail and wish to retake the test should resubmit the form along with an additional fee (if required).


2. Print or type your name and address. Be sure to place your ASPE membership number in the appropriate space.

3. Answer the multiple-choice continuing education (CE) questions based on the corresponding article found on www.psdmagazine.org and the appraisal questions on this form.

4. Submit this form with payment ($35 for nonmembers of ASPE) if required by check or money order made payable to ASPE or credit card via mail (ASPE Education Credit, 8614 W. Catalpa Avenue, Suite 1007, Chicago, IL 60656) or fax (773-695-9007).


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PS&D Continuing Education Answer SheetIrrigation Systems (PSD 141)

Questions appear on page 8. Circle the answer to each question.Q 1. A B C DQ 2. A B C DQ 3. A B C DQ 4. A B C DQ 5. A B C DQ 6. A B C DQ 7. A B C DQ 8. A B C DQ 9. A B C DQ 10. A B C DQ 11. A B C DQ 12. A B C D

Appraisal QuestionsIrrigation Systems (PSD 141)






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Expiration date: Continuing education credit will be givenfor this examination through September 30, 2008.Applications received after that date will not be processed.


Payment: Personal Check (payable to ASPE) $ ___________ Business or government check $ ________ DiscoverCard VISA MasterCard AMEX $ ___________If rebilling of a credit card charge is necessary, a $25 processing fee will be charged.ASPE is hereby authorized to charge my CE examination fee to my credit card.





PSD

129

Jail and Prison Housing Units


SEPTEMBER/OCTOBER 2005

PSDMAGAZINE.ORG


Continuing Education

INTRODUCTIONTheobjectiveof thischapter is tohelp thedesignerunder-standanddealwiththeproblemsofdesigningwaterheatingsystemsforjailandprisonhousingunits.Itisimportantthatthedesignerrecognizethateachbuildingisuniqueandworkcloselywiththeowner,architect,andgovernmentauthoritiestodeterminehowabuildingwilloperate.Abuilding’sopera-tionwill affectwhenand forhow long thepeakhotwaterdemandwilloccur.

The first part of this chapter discusses generally some ofthedesign criteria andareasof special concern involved indesigningfor jailandprisonhousingunits.Thesecondpartgivestwopracticalexamplesofsizingmethodology,oneforjailsandoneforprisons.

GENERALThe design criteria used to design hot water systemsforjailhousingunitsdifferfromthoseusedforprisonhous-ingunits.Thisdifferenceisduetothefact that thefacilitiesareusedfordifferentpurposes.Jailsareusedprimarilyto house peopleawaiting trialor serving short sentences.Prisonsareusedtohouseconvictedcriminalsservinglongprisonterms.Thisdifferenceaffectstheprisoners’dailyrou-tines,which,inturn,determinewhenthefacilities’peakhotwaterdemandsoccur.

Itisrequiredthathotwatertemperaturefortheshowersandlavatoriesinjailsandprisonsbelimitedtobetween100and110°F(38and43°C).Thistemperaturerangehasbeenestab-lishedtopreventinmatesfromusinghotwaterasaweapon.1The generally used standard temperature is 105°F (41°C).Push-buttontypeself-closingortimed-controlvalvesareusedtodeliverhotwaterof this temperature to theshowersandlavatories.Occasionallyanownerwillrequirethatashowercontrolvalvethatallowssomeinmatecontrolofshowerwatertemperature beprovided.New security type valves providethisfeature.Hotwateratthedesigntemperaturemustbefur-nished at the fixture because of the lower-than-usualwatertemperature and the self-closing features of inmate controlvalves.

Thedesignershouldtakeintoconsiderationthatthetypicallifeofajailorprisonis50to100yearsandthatanysysteminstalledmustbeaccessibleforreplacementorrepair.

Largejailfacilitiesandallprisonshavecentrallaundryfacili-tiesandcentralkitchens.Thehotwatersystemsforthelaundryandkitchenareasshouldbeseparatefromthoseforhousingbecausetheseareashaveverydifferenthotwaterdemands.Forinstance,thetemperatureofthehotwaterdeliveredwillbehigher,between140and180°F(60and82°C).Ifacentral-izedwaterheatingsystemisusedforthegeneralpurposeandkitchen/laundrywater,thenafail-safewatertemperingsystemmustbeinstalledforthegeneralpurposewater.

Hot Water DemandTheusualfixturesrequiringhotwaterfoundinhousingunitsareshowersandlavatories.Someunitsalsohavesmallkitch-ens or serving areas,whichmay have additional sinks andsmalldishwashers.Suchservingareasareprojectspecific.Injails,veryoftenoneortworesidentialtypewashingmachinesarerequiredforeachhousingunitpod(agroupof10to20cells).Thetypicalhousingunitiscomposedofmultiplepods,witheachcellopeningontoadayroom.Currentlyitisrecom-mendedthattherebeoneshowerforeveryeightinmatesand a lavatory in each cell.2 The number and location oftheshowersaredecidedbythearchitectincoordinationwiththeownerandaccordingtospecificcoderequirements.Theshoweroperation is the factor that determines the requiredsizesofthewaterheaterandstoragetank.

Primary considerations1. Thestandardrecommendationofeightinmatesper

showerwasmadesothatallinmatescouldshowerduringa1-hperiod.Thisarrangementallowsanaverageof7minforeachinmatetoshower.Abouthalfthattimeistakenupbydryingandswitchinginmates,leavingonlyabout3.5minofactualwaterusageperinmate.

2. Showersarethemainfactoraffectingwaterheatersize.Allowanceshouldbemadeforthemanylavatoriesinhousingunitswhensizingthestoragetank.

3. Theefficiencyofstoragesystemsvariesfrommanu-facturertomanufacturer,but65to80%isagoodefficiencyrangetouseuntilyouhaveactualdataonthetankandsystemspecified.

JAIL EXAMPLEThisisanexampleofajailhousingunitwithsixpodsof24cellseach(oneinmatepercell)andthreeshowersperpod.Assumethatthehotwatergeneratedis140°F(60°C)andtheincomingwatertemperatureis50°F(10°C).

Questions1. Willtheinmatesberequiredtoshowerataspecifictime?

• No2. Willallthecellpodsreleasetheirinmatesforshowering

withinthesamehour?

• Yes.(Thismeansthatthedesignmustaccommodatea1-hrecoveryperiod.)

3. Willtheshowerdurationperinmatebelimited?

• Yes,to7minperinmate,with3.5minofwaterusage4. Doesthefacilityanticipatedoublebunkinginmates,either

noworinthefuture?

• No

Calculations for Jail Housing UnitsThe ratio of 140 to 50°F (60 to 10°C)water flowing at theshower can be calculated using the mixed-water formula,Equation1.7,fromChapter1:

Jail and Prison Housing Units

1American Corrections Association, Adult Corrections Institutions, 3d ed.2 Ibid.

Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations.

Sept/Oct 2005 • PlumbingSystems&Design 57


P=(Tm–Tc)(Th–Tc)where

P=Percentageofmixturethatishotwater Tm=Temperatureofmixedwater=105°F(41°C) Th=Temperatureofhotwater=140°F(60°C) Tc=Temperatureofcoldwater=50°F(10°C)

P= 105–50 = 55 =0.61140–50 90

[P= 41–10 = 31 =0.61]60–10 50

Witheachshowerflowing2.5gpm(0.13L/sec), 2.5gpm×0.61=1.53gpmwillbe140°Fhotwater

(0.13L/sec•0.61=0.08L/secwillbe60°Chotwater)

8inmates×3.5min=28minofwaterflowingpershowerduringthepeakhour

6pods×3showersperpod=18showerstotal

18showers×28min=504min

504min×1.53gpm=771.12gal140°Fhotwaterperpeakhourdemand

(504min•0.10L/sec• 60sec/min=3024L60°Chotwaterperpeakhourdemand)

Atthistimeajudgmentwillhavetobemadebythedesignerastowhetherornottheauxiliaryequipmentwillbeoperatingduringthepeakhour.Forthisexample,wewillassumeitwillnot.

Auxiliary Equipment Demand Doortypedishwasherwithinternalheater=69gph

(261.17L/h)

Singlecompartmentsink=30gph(113.55L/h)

Clotheswashingmachines,1perpod×6pods=6

6×2loads@20gal/load=240gph

(6 •[email protected]/load=908.40L/h)

Auxiliaryequipmentdemandfor140°Fwater=339gph

(Auxiliaryequipmentdemandfor60°Cwater=1283.12L/h)

Assuming that operation of the auxiliary equipment doesnot coincidewith thepeakhourdemand, sizing theheaterand storage tank to handle the additional load will not benecessary.Theheater size required for inmate showering ismorethantwicethesizeneededfortheauxiliaryequipmentdemand.

Recommendation

Heater sizingTwoheatersshouldbeselected,eachsizedtoservebetween60 and 100% of the total demand. In prison housing unitssome redundancy in thewater heating system is necessary.Thelevelofredundancyshouldbediscussedwiththefacility’sowners.

Storage tank sizingIfthewaterheaterissizedtomeettherecoveryrequiredtohandle the peak shower demand, the storage tankmay be

sized to handle approximately 50% of the shower demandduring theperiodofpeakuse.The storage tank shouldbelargeenough toprevent theheater fromcyclingonandoffmore than four times per hour during off-peak hours. Thisrequirementnecessitatesfindingabalancebetweenexcessivetanksizeandshortcycling.Calculation

771.12gph×0.50=385.6gal

(2.93m3/h •0.50=1.47m3/h)

385.6 =481.6galstoragetanksize0.80

[ 1470L =1837.5Lstoragetanksize ]0.80

Theauxiliaryequipmentdemandof339gph(1283.12L/h)willhavethegreatestinfluenceontheamountofcyclingdonebytheheaterduringoff-peakhours.

339gph =5.56gpmaverageflowof140°Fwater60

[ 1283.12L/h =0.36L/secaverageflowof60°Cwater ]60•605.56gpm×15min=83.4gal

(0.36L/sec •60sec/min •15min=324L)

83.4 =104.25galstorage0.80

[ 324L =405Lstorage]0.80

Theselectedsizeofa481.6-gal (1837.5-L) storage tank ismorethanadequatetomeetthisdemand.

PRISON EXAMPLEThis is an example of a housing facility for 384 inmates. Ithasfourwings(96inmatesperwing)andeachwinghasfourstories(24inmatesperwingperstory).Acentralkitchenandlaundryarelocatedinaseparatebuilding.Showerareasareprovidedoneveryfloorofeverywing,andeachoftheseareashasthreeshowerheads.

Design Criteria and Assumptions1. Inmatelavatoriesandshowerswillbesuppliedwith105°F

(41°C)circulatedhotwater.Showersaretohave2.5gpm(0.16L/sec)flowrestrictorsandlavatories2.0gpm(0.13L/sec)flowrestrictors.

2. Therewillbeseparatesystemsforthekitchenandlaun-dryareas.

3. Thewatertemperatureforthelaundryareawillbe180°F(82°C)andforthekitchenarea140°F(60°C),plustherewillbeaseparateloopof105°F(41°C)waterforthehandwashinglavatoriesandtoiletslocatedinthekitchenarea.

4. Waterat140°F(60°C)willbesuppliedtothedishwasher.Thedishwasherwillhaveaseparateboosterheatertoraisewatertemperaturetothe180°F(82°C)requiredforthefinalrinsecycle.

5. Thestoragetankcapacityvariesconsiderably—from0%forinstantaneousheaterstomorethan100%.Check

Reprinted from Domestic Water Heating Design Manual, 2nd ed. 2003. Chicago: American Society of Plumbing Engineers. Chapter 9, “Jail and Prison Housing Units” (pp. 179-188). © 2003, American Society of Plumbing Engineers.

Continuing Education: Jail and Prison Housing Units

5 PlumbingSystems&Design • Sept/Oct 2005


todetermineiftheownerhasapreference.Remember,mostownersalreadyoperateexistingjailsorprisons;theymayhaveestablisheddesignparameters.Theinitialcostofequipment,theunitperformance,andoperatingcostsarealsofactorstobeconsideredwhensizingthestoragetank.

6. Lookforadditionalsupportfacilities,suchasthebarbershop,pantries,oranemergencymedicalclinic.

7. Althoughoperatinghoursforthelaundryareaaregener-allyfrom8:00A.M.to5:00P.M.,reviewoperationaltimesandscheduleswiththeowner.

8. Sourcesofheat:Theselectionofsteam,naturalgas,orelectricitywillhaveanenormousimpactonthetypeofheaterandonenergyconsumption.

Note:Acentralsteamgenerationplantmayfavoraninstan-taneoustypesteam-to-hot-waterconverterwithminimumhotwaterstorageforsurges.Remember,redun-dancyinheatersisalwaysrequiredforjailsandprisonstoallowforproblemscreatedbyinmates.Thecostofgen-eratinganddistributingsteamisalsoafactortobeconsid-ered.

9. Themethodtouseforsizingthewaterheaterandstoragetankmaybedeterminedbytheowner/operatorofthefacility.

10.Oneinmatepercellequals384inmates.Aquestionthatshouldbeaskediswhethertheownerplanstoexpandinthefuturebyputtingmorethanoneinmateineachcell.

Questions1. Willtheinmatesberequiredtoshowerataspecifictime?

• No2. Willtheshowerdurationperinmatebelimitedordo

inmateshavecontroloverwhentheyshower?

• Showersarelimitedto7minperinmate,with3.5minofwaterusagepershower.

3. Willallofthecellpodsreleasetheirinmatesforshoweringwithinthesamehour?

• Yes.(Thismeansthatthedesignmustaccommodatea1-hrecoveryperiod.)

4. Doesthefacilityanticipatedoublebunkingtheinmatesnoworinthefuture?

• No5. Doesthefacilityhaveawork-releaseprogram?

• Yes6. Whatisthetimeallocatedforthework-releaseinmates

toshowerpriortoleavingfortheirdutiesinthework–releaseprogram?

• Onehour,atthesameapproximatetimeastheotherinmates.

Calculations for Inmate Housing UnitsRefertothecalculationsdoneforthejailexampleforthemeth-odology for determining the 1.53 gpm (0.1 L/sec) flowpershowerheadandtheoperationtimeof28minpershower.

48showers×28min=1344min

1344min×1.53gpm=2056galof140°Fhotwaterforpeakhourdemand

(1344min•0.096L/sec•60sec/min=7741.44L/hof60°Chotwaterforpeakhourdemand)

Storage Tank SizingInthisexample,inmatelavatorieswillhavetheonlyimpactontanksizingbecausethekitchenandlaundrywillhaveseparatesystems.

If thewaterheater is sized tomeet the recovery requiredtohandlethepeakshowerdemand,thestoragetankmaybesized to handle approximately 50% of the shower demandduring theperiodofpeakuse.The storage tank shouldbelargeenough toprevent theheater fromcyclingonandoffmore than four times per hour during off-peak hours. Thisrequirementnecessitatesfindingabalancebetweenexcessivetanksizeandshortcycling.Calculation

2056gph×0.50=1028gal140°Fhotwater

(7.74m3/h•0.50=3.87m360°Chotwater)

1028gal =1285galstoragetanksize0.80eff.

[ 3870L =4837.5Lstoragetanksize ]0.80eff.

Kitchen Considerations1. Theitemthathasthegreatesteffectonhotwaterdemand

isthedishwasher.Somecentralkitchensdonothavediningareas,inwhichcaseallmealsareshippedtothehousingunitsinbulkfordistributionandthedishwashersareinthehousingunits.

2. Thetemperatureofthehotwatergoingtokitchenlavato-riesshouldnotexceed110°F(43°C)forsafetyreasons.

3. Checktoseeifthedishwasherhasaboosterheateranddeterminethetypeofenergyused(steamorelectric-ity).Thisinformationwillhelpyoudecidewhetherornottogenerate180°F(82°C)water.

Note:Somedishwashersonthemarketusechemicalsfordisinfecting,thusthehigherwatertemperatureisnotrequired.

4. Afterdishwashers,compartmentsinksarethenextlargestuserof140°F(60°C)hotwater.Thehighertemperatureisrequiredtocutthroughgreaseonpotsandpans.Somethree-compartmentsinkshaveboosterheatersintherinsetanktomaintainthehighertemperature.

5. Otherkitchenitemsthatusehotwateraretheprerinseforthedishwasher,thevegetablesinks,andthecartwash-downhosebibs.

6. Alwayscheckthekitchenconsultant’splansforhotwaterrequirements.

7. Refertothe“Hospitals”chapterforadditionalinformationonkitchens.

Laundry Considerations1. Reviewthelaundryconsultant’splansanddeterminethe

typeofwashingmachine/extractorused.Prisonlaun-driesaresimilartohospitallaundriesinthattheyprocesssheets,pillowcases,anduniforms.Thesizeandnumber



of machines are normally decided by the owner or the consultant.

2. Inmates each generate about 30 lb (13.61 kg) of laundry a week. This consists of 1 pillowcase, 2 sheets, 1 towel, and uniforms.

3. Additionally, prison laundries usually handle the uniforms of the correctional officers.

4. Sometimes prison laundries do laundry for outside hospi-tals as a prison industry.

5. Consider the feasibility of a heat recovery system that uses the wash-water discharge. The laundry consultant can probably advise you about this.

6. Laundry equipment suppliers are the only reliable source of information on the hot water demands and required temperaures of their washers. They can tell you how many gallons (liters) of water the machines require and the maximum number of cycles per hour they will oper-ate.

7. Washers demand their hot water fast. It is not unusual for a 2-in. (DN50) hot water line to be connected to the larger

washers. Therefore, larger than normal storage capacity is needed to handle the surges in hot water demand. One rule of thumb is to provide 75% of the maximum hourly demand in storage; don’t provide less than 50% of that amount.

8. In 1992 a new federal law (“Bloodborne Pathogen”) was passed to protect workers against the human immunodefi-ciency virus (HIV) and hepatitis B virus (HBV). All deten-tion facilities are now under this new federal regulation. A major/critical new standard was created by the law: “When an officer’s uniform becomes contaminated with blood products, the officer cannot leave his workplace with the uniform on. The facility must clean that uniform and reissue it to the officer.” The law states further that “inmate labor cannot be used when handling blood con-taminated items.”

A washer and dryer for the aforementioned are required to achieve compliance with the law. They should be located in a space that is under the direct supervision of an officer so the security of the officers’ uniforms will not be jeopardized. n

Continuing Education: Jail and Prison Housing Units

60 PlumbingSystems&Design • Sept/Oct 2005


1. The sizing of a domestic water storage tank shall be large enough to prevent the water heaters from cycling no more than ____________ times per hour during off-peak hours.a. twob. fourc. sixd. eight

2. What are some of the most important factors to consider when sizing a domestic hot water storage tank?a. operating costsb. initial costsc. unit performanced. all of the above

. The American Corrections Association ____________.a. has established the hot water requirements for jails and

prisonsb. requires the temperature of the hot water at inmate

showers be between 100oF and 110oFc. has established the generally used standard of 105oF for

inmate showersd. requires the use of push button type showers

4. A typical hot water delivered temperature for inmate lavatories is ____________oF.a. 95b. 100c. 105d. 110

. If the water heater is sized to meet the recovery required to handle the peak shower demand of a jail housing unit, ____________.a. the storage tank may be sized to handle approximately

50% of the shower demandb. the storage tank should be large enough to prevent the

heater from cycling on and off more than four times per hour during off-peak hours

c. the storage tank should be 481.6 gallonsd. both a and b

6. The main factor to consider in sizing a water heating system for a jail is ____________.a. showersb. the many lavatories in housing unitsc. the temperature of the hot water to be provided and the

duration of the peak flowd. the efficiency of the storage system

. Each inmate generates approximately ____________ pounds of laundry per week.a. 10b. 20c. 30d. 40

8. In what year was the Bloodborne Pathogen law passed that was intended to protect workers against human immunodeficiency virus (HIV) and the hepatitis B virus (HBV)?a. 1986b. 1992c. 1998d. 2004

. Auxiliary equipment demand ____________.a. must be included in the water heating sizingb. must be assumed to not be in operation during the

shower periodc. should be determined whether or not it will be operating

during the peak hourd. is equal to 69 gallons per hour

10. The item of kitchen equipment that has the greatest effect on the hot water demand is the ____________.a. vegetable prep sinkb. triple pot sinkc. dishwasherd. exhaust hood washdown system

11. A jail housing pod of 20 cells, each with one inmate, would require how many showers?a. one per cellb. threec. fourd. the number is determined by the architect

12. The objective of this chapter is ____________.a. to help government authorities determine how the

building will operateb. to help the designer understand and deal with the

problems of designing water heating systems for jail and prison housing units

c. to help the designer understand and deal with the problems of designing water heating equipment for jail and prison housing units

d. all of the above

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ASPE features a technical article in every issue of PSD, excerpted from its own publications. Each article is followed by a multiple-choice test and a simple reporting form.

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Continuing Education from Plumbing Systems & DesignKenneth G.Wentink, PE, CPD, and Robert D. Jackson, Chicago Chapter President

CE Questions—“Jail and Prison Housing Units” (PSD 129)




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PSD Continuing Education Answer SheetJail and Prison Housing Units (PSD 129)

Questions appear on page 61. Circle the answer to each question.Q 1. A B C DQ 2. A B C DQ . A B C DQ 4. A B C DQ . A B C DQ 6. A B C DQ . A B C DQ 8. A B C DQ . A B C DQ 10. A B C DQ 11. A B C DQ 12. A B C D

Appraisal QuestionsJail and Prison Housing Units (PSD 129)






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PlumbingSystems&Design • Sept/Oct 2005


PSD

134

Life-Safety Systems


JULY/AUGUST 2006

PSDMAGAZINE.ORG


IntroductIonA threat to personnel safety often present in pharmaceutical facilities is accidental exposure and possible contact with toxic gases, liquids, and solids. This chapter describes water-based emergency drench equipment and systems commonly used as a first-aid measure to mitigate the effects of such an accident, Also described are the breathing-air systems that supply air to personnel for escape and protection when they are exposed to either a toxic environment resulting from an accident or normal working conditions that make breathing the ambient air haz-ardous.

EmErgEncy drEnch-EquIpmEnt SyStEmS

gEnEralWhen toxic or corrosive chemicals come in contact with the eyes, face, and body, flushing with water for 15 min with the clothing removed is the most recommended first-aid action that can be taken by nonmedical personnel prior to medical treat-ment. Emergency drench equipment is intended to provide a sufficient volume of water to effectively reach any area of the body exposed to or has come into direct contact with any inju-rious material. Within facilities, specially designed emergency drench equipment, such as showers, drench hoses, and eye and face washes, are located adjacent to all such hazards. Although the need to protect personnel is the same for any facility, specific requirements differ widely because of architectural, aesthetic, location, and space constraints necessary for various industrial and laboratory installations.

SyStEm claSSIfIcatIonSDrench equipment is classified into two general types of system based on the source of water. These are plumbed systems, which are connected to a permanent water supply, and self-contained or portable equipment, which contains its own water supply. Self-contained systems can be either gravity feed or pressur-ized.

One type of self-contained eyewash unit is available that does not meet code requirements for storage or delivery flow rate. This is called the personnel eyewash station and is selected only to supplement, not replace, a standard eyewash unit. It consists of a solution-filled bottle(s) in a small cabinet. This cabinet is small enough to be installed immediately adjacent to a high hazard. If an accident occurs, the bottle containing the solu-tion is removed and used without delay to flush the eyes while waiting for the arrival of trained personnel and during travel to a code-approved eyewash or first-aid station.

codES and StandardS1. ANSI Z-358.1, Emergency Shower and Eyewash Equipment.2. OSHA has various regulations for specific industries per-

taining to the location and other criteria for emergency eyewashes and showers.

3. The Safety Equipment Institute (SEI) certifies that equip-ment meets ANSI standards.

4. Applicable plumbing codes.

For the purposes of the discussion in this section on drench equipment, the word “code” shall refer to ANSI Z-358.1.

typES of drEnch EquIpmEntEmergency drench equipment consists of showers, eyewash units, face-wash units, and drench hoses, along with intercon-necting piping and alarms if required. All of these units are available either singly or in combination with each other. Ancil-lary components include thermostatic mixing systems, freeze protection systems and enclosures. Each piece of equipment is designed to perform a specific function. One piece is not intended to be a substitute for another, but rather, to comple-ment the others by providing additional availability of water to specific areas of the body as required.

Emergency ShowersPlumbed Showers Plumbed emergency showers are perma-nently connected to the potable water piping and designed to continuously supply enough water to drench the entire body. A unit consists of a large-diameter shower head intended to distribute water over a large area. The most commonly used type has a control valve with a handle extending down from the valve on a chain or rod that is used to turn the water on and off manually. Code requires the shower be capable of delivering a minimum of 30 gpm (113.6 L/min) of evenly dispersed water at a velocity low enough so as not to be injurious to the user. Where this flow rate is not available, 20 gpm (75.7 L/min) is acceptable if the shower-head manufacturer can show the same spray pat-tern required for 30 gpm can be achieved at the lower flow rate. The minimum spray pattern shall have a diameter of 20 in. (58.8 cm), measured at 60 in. (152.4 cm) above the surface on which the user stands. This requires a minimum pressure of approxi-mately 30 psi (4.47 kPa). Emergency showers can be ceiling mounted, wall mounted or floor mounted on a pipe stand, with the center of the spray at least 16 in. (40.6 cm) from any obstruc-tion. Showers should be chosen for the following reasons:1. When large volumes of potentially dangerous materials are

present.2. Where a small volume of material could result in large

affected areas, such as in laboratories and schools.

A typical emergency shower head mounted in a hung ceiling is illustrated in Figure 1.

Self-Contained Showers Self-contained emergency show-ers have a storage tank for water. Often this water is heated. The shower shall be capable of delivering a minimum of 20 gpm (75.5 L/min) for 15 min. The requirements for mounting height and spray pattern are the same as they are for plumbed show-ers.

Life-Safety Systems

Reprinted from Pharmaceutical Facilities Plumbing Systems, Chapter 8: “Life-Safety Systems,” by Michael Frankel. © American Society of Plumbing Engineers.




Emergency EyewashPlumbed Eyewash Emergency eyewashes are specifically designed to irrigate and flush both eyes simultaneously with dual streams of water. The unit consists of dual heads in the shape of a “U,” each specifically designed to deliver a narrow stream of water, and a valve usually controlled by a large push plate. Code requires the eyewash to be capable of delivering a minimum of 0.4 gpm (1.5 L/min). Many eyewashes of recent manufacture deliver approximately 3 gpm (11.4 L/min). Once started, the flow must be continuous and designed to operate without the use of the hands, which shall be free to hold open the eyelids. The flow of water must be soft to avoid additional injury to sensitive tissue. To protect against airborne contaminants, each dual stream head must be pro-tected with a cover that is automatically discarded when the unit is activated. The head covers shall be attached to the heads by a chain to keep them from being lost. The eyewash can be mounted on a coun-ter or wall, or as a free stranding unit attached to the floor. The eyewash could be provided with a bowl. The bowl does not increase the efficiency or usefulness of the unit but aids in identification by personnel. It is common practice to mount a swivel type eyewash on a laboratory sink faucet, installed so it can be swung out of the way during normal use of the sink but can be swung over the sink bowl in order to be operated in an emergency.

The code recommends (but does not require) the use of a buffered saline solution to wash the eyes. This could be accomplished with a separate dispenser filled with concentrate that will introduce the proper solution into the water supply prior to reaching the device head. A commonly used device is a wall-mounted, 5 to 6-gal (20 to 24-L) capacity solution tank connected to the water inlet dispenses a mea-sured amount of solution when flow to the eyewash is activated. A backflow device shall be installed on the water supply.

Self-Contained Eyewash A typical self-con-tained eyewash has a storage tank with a minimum 15-min water supply. The mounting height and spray pattern requirements are the same as those for a plumbed eyewash.

Emergency Face WashThe face wash is an enhanced version of the eyewash. It has the same design requirements and configura-tion, except the spray heads are specifically designed to deliver a larger water pattern and volume will flush the whole face and not just the eyes. The face wash should deliver approximately 8 gpm (55 L/min). The stream configuration is illustrated in Figure 2. Very often, the face wash is chosen for combination units. In general, the face wash is more desirable than the eyewash because it is very likely an accident will affect more than just the eyes. All dimensions and requirements of the free-standing face wash are similar to those for the eyewash.

Drench HosesA drench hose is a single-head unit connected to a water supply with a flexible hose. The head is gener-ally the same size as a single head found on an eye/

face wash. Code requires the drench hose be capable of deliver-ing a minimum of 0.4 gpm (1.5 L/min). It is controlled either by a squeeze handle near the head or a push-plate ball valve located at the connection to the water source. It is used as a supplement to showers and eye/face washes to irrigate specific areas of the body. Drench hoses are selected for the following reasons:1. To spot drench a specific area of the body when the large

volume of water delivered by a shower is not called for.2. To allow irrigation of an unconscious person or a victim

who is unable to stand.3. To irrigate under clothing prior to the clothing’s removal.

Figure 2 Combination Emergency Shower, Eye/Face Wash, and Drench Hose Unit

Figure 1 Typical Emergency Shower



Combination EquipmentCombination equipment consists of multiple-use units with a common water supply and supporting frame. Combinations are available that consist of a shower, eye/face wash, and drench hose in any configuration. The reason for the use of combina-tion equipment is usually economy, but the selection should be made considering the type of irrigation appropriate for the potential injuries at a specific location. For combination units, the water supply must be larger, capable of delivering the flow rate of water required to satisfy two devices concurrently rather than only a single device.

The most often-used combination is the drench shower and face wash. Figure 2 illustrates a combination shower, eye/face wash and drench hose complete with mounting heights.

drEnch EquIpmEnt componEntS

ControlsOften referred to as “activation devices,” controls cause water to flow at an individual device. Stay-open valves are required by code in order to leave the hands free for the removal of clothing or for holding eyelids open. The valves most often used are ball valves with handles modified to provide for the attachment of chains, rods, and push plates. In very limited situations, such as in schools, valves that automatically close (quick-closing) are permitted if they are acceptable to the facility and authorities having jurisdiction.

Valves are operated by different means to suit the specific hazard, location, durability, and visibility requirements. The operators on valves are handles attached to pull rods, push plates, foot-operated treadle plates and triangles. A solid pull rod is often installed on concealed showers in order to push the valve closed after operation. Another method is to have two handles attached to chains that extend below the hung ceiling, one to turn on the valve and another handle to turn it off. Chains are used if the handle might be accidentally struck, they enable the handle to move freely and not injure the individual who might accidentally strike the hanging operator.

Operating handles for the physically challenged are mounted lower than those for a standard unit. In many cases, this requires that operating handles be placed near walls to keep them out of traffic patterns where they would be an obstruction to able-bodied people passing under them. A free-standing combination

shower and eyewash that is handicapped accessible using handles hung from the ceiling is illustrated in Figure 3. The handle must be located close enough to the center of the shower to be easily reached, which is about 2 ft 0 in. from the center of the shower.

AlarmsAlarms are often installed to alert security or other rescue per-sonnel that emergency drench equipment has been operated and to guide them rapidly to the scene of the accident. Com-monly used alarms are audible and visual devices—such as flashing or rotating lights on top of, or adjacent to, a shower or eyewash—and electronic alarms wired to a remote security panel. Remote areas of a plant are particularly at risk if person-nel often work alone. Alarms are most often operated by a flow switch activated by the flow of water when a piece of equipment is used.

When tempered water systems are used to supply drench equipment, a low water temperature of 60°F shall cause an alarm annunciation.

Flow-Control DeviceWhere water pressure exceeds 80 psig (550 kPa) or if the differ-ence in water pressure between the first and last shower head is more than 20 psig (140 kPa), it is recommended that a self-adjusting flow-control device be installed in the water-supply pipe. Its purpose is to limit the flow to just above the minimum required by the specific manufacturer for proper functioning of equipment. Such devices are considered important because a shower installed at the beginning of a long run has a much greater flow than the device at the end. During operation, the higher pressure could cause the flow rate to be as much as 50 gpm (L/min). If no floor drain is provided, the higher flow for 15 min at the higher pressure could produce a much greater amount of water that must be cleaned up and disposed of after-wards. Drench hoses and eye and face washes are not affected because of their lower flow rates and their flow head designs.

Where pressure-reducing devices are required for an entire system, they should be set to provide approximately 50 psig (345 kPa).

SyStEm dESIgn

GeneralIt is a requirement that a plumbed system be connected to a potable water supply as the sole source of water. This system is therefore subject to filing with a plumbing or other code offi-cial for approval and inspection of the completed facility, as are standard plumbing systems.

An adequately sized pipe with sufficient pressure must be provided from the water supply to meet system and device operating-pressure requirements for satisfactory functioning. One maintenance requirement is that the water in the piping system be flushed to avoid bacterial growth.

It is common practice to add antibacterial and saline products to a self-contained eyewash unit and an antibacterial additive to an emergency shower. Water is also commonly used if it can be changed every week. It is well established that no preservative will inhibit bacterial growth for an extended period of time. Self-contained equipment must be checked regularly to determine if the quality of the stored water has deteriorated to a point where it is not effective or safe to use.

If valves are placed in the piping network for maintenance purposes, they should be made for unauthorized shut-off.

Figure 3 Clearance Dimensions Around Shower and Eye/Face Wash


CONTINUING EDUCATION: Life-Safety Systems


Water-Supply Pressure and Flow RatesEmergency showers require between 20 and 30 gpm (76 to 111 L/min), with 30 gpm recommended. The minimum pressure required is 30 psig (4.5 kPa) at the farthest unit, with a generally accepted maximum pressure of 70 psi (485 kPa). Code mentions a high pressure of 90 psig (612 kPa), which is generally consid-ered to be excessive. Most plumbing codes do not permit water pressures as high as 90 psig. Generally accepted practice limits the high water pressure to between 70 and 80 psig (480 and 620 kPa).

Most eyewash units require a minimum operating pressure of 15 psig (105 kPa) with a flow rate minimum of 3 gpm (12 L/min) at the farthest unit. Maximum pressure is similar to that for showers. Face washes and drench hoses require a minimum operating pressure of 15 psig (105 kPa) with a minimum flow rate of 8 gpm (30 L/min) at the farthest unit.

System Selection

Plumbed SystemThe advantages of a plumbed system include:1. Permanent connection to a fresh supply of water, requiring

no maintenance and only minimum testing of the devices to ensure proper operation.

2. It provides an unlimited supply of water often at larger vol-umes than self-contained units.

Disadvantages include:1. Higher first cost than a self-contained system.2. Maintenance is intensive. Such systems require weekly

flushing, often into a bucket, to remove stagnant water in the piping system and replace it with fresh water.

Self-Contained SystemAdvantages of the self-contained system include:1. Lower first cost compared to a plumbed system.2. Can be filled with a buffered, saline solution, which is rec-

ommended for washing eyes.3. Available with a container to catch waste water.4. Portable units can be moved to areas of greatest hazard

with little difficulty.5. A gravity eyewash is more reliable. The water supply can be

installed where there is room above the unit. If not, a pres-surized unit mounted remotely should be selected.

Disadvantages include:1. Only a limited supply of water at a lesser flow rate is avail-

able.2. The stored liquid must be changed on a regular basis to

maintain purity.

The plumbed system is the type of system selected most often because of the unlimited water supply.

Pipe Sizing and MaterialIn order to supply the required flow rate to a shower, a mini-mum pipe size of 1 in. (25 mm) is required by code, with 1¼ in. (30 mm) recommended. If the device is a combination unit, a 1¼-in. size should be considered as minimum. An emergency eye/face wash requires a minimum ½ in. (13 mm) pipe size.

Except in rare cases where multiple units are intended to be used at once, the piping system size should be based on only one unit operating. The entire piping system is usually a single size pipe based on the requirements of the most remote fixture.

Appropriate pressure loss calculations should be made to ensure the hydraulically most remote unit is supplied with adequate pressure with the size selected. Adjust sizes accordingly to meet friction loss requirements.

The pipe material should be copper to minimize clogging the heads of the units in time with the inevitable corrosion products released by steel pipe. Plastic pipe (PVC) should be considered where excessive heat and the use of closely located supports will not permit the pipe to creep in time.

Emergency drench equipment shall be sized based on the single highest flow rate, usually 30 gpm (115 L/min) for an emergency shower. Piping is usually a 1¼-in. header of copper pipe for the entire length of a plumbed system.

Flushing Water DisposalWater from emergency drench equipment is mainly discharged onto the floor. Individual eye/face washes mounted on sinks discharge most of the water into the adjacent sink. Combination units have an attached eye/face wash also discharge water on the floor. There are different methods of disposing of the water resulting from an emergency device depending on the facility. The basic consideration is whether to provide a floor drain adja-cent to a device to route that water from the floor to a drainage system.

It is accepted practice not to provide a floor drain at an emer-gency shower. Experience has shown in most cases, particularly in schools and laboratories, it is easier to mop up water from the floor in the rare instances emergency devices are used rather than add the extra cost of a floor drain, piping and a trap primer. Considerations include:1. If the drain is not in an area where frequent cleaning is

done, the trap may dry out, allowing odors to be emitted.2. Is there an available drainage line in the area of the device?3. Can the chemical, even in a diluted state, be released into

the sanitary sewer system or must it be routed to a chemical waste system for treatment?

4. Must purification equipment be specially purchased for this purpose?

InStallatIon rEquIrEmEntS for drEnch EquIpmEntThe need to provide emergency drench equipment is deter-mined by an analysis of the hazard by design professionals or health or safety personnel and by the use of common sense in conformance with OSHA, CFR, and other regulations for spe-cific occupations. Judgment is necessary in the selection and location of equipment. Very often, facility owners have specific regulations for its need and location.

Dimensional RequirementsThe mounting height of all equipment, as illustrated in ANSI Z-358.1, is shown in Figure 2. If the shower head is free-standing, the generally accepted dimension for the mounting height is 7 ft 0 in. (2.17 m) above the floor. Generally accepted clearance around showers and eye/face washes is illustrated in Figure 3. A wheelchair-accessible, free-standing, combination unit is illus-trated in Figure 4.

Equipment LocationThe location of the emergency drench equipment is crucial to the immediate and successful first-aid treatment of an accident victim. It should be located as close to the potential hazard as is practical without being affected by the hazard itself or potential accidental conditions, such as a large release or spray of chemi-



cals resulting from an explosion or a pipe and tank rupture. Another location problem is placement adjacent to electrical equipment. Location on normal access and egress paths in the work area will reinforce the location to personnel, who will see it each time they pass.

There are no requirements in any code pertaining to the loca-tion of any drench equipment in terms of specific, definitive dimensions. ANSI code Z-358.1 requires emergency showers be located a maximum distance of either 10 seconds travel time by an individual or no more than 75 ft (22.5 m) from the potential protected hazard, whichever is shorter. If strong acid or caus-tic is used, the equipment should be located within 10 ft (3 m) of the potential source of the hazard. The path to the unit from the hazard shall be clear and unobstructed, so impaired sight or panic will not prevent clear identification and access. There is no regulation as to what distance could be covered by an indi-vidual in 10 seconds. There are also no specific provisions for the physically challenged.

Since there are no specific code requirements for locat-ing drench equipment, good judgment is required. Accepted practice is to have the equipment accessible from three sides. Anything less generally creates a “tunnel” effect that makes it more difficult for the victim to reach the equipment. It should be located on the same level as the potential hazard when possible.

Traveling through rooms that may have locked doors to reach equipment shall be avoided, except placing emer-gency showers in a common corridor, such as outside individual laboratory rooms, is accepted practice. Care should be taken to avoid locating the shower in the path of the swinging door to the protected room to prevent personnel coming to the aid of the victims from knock-ing them over.

Emergency eye/face washes should be located close to the potential source of hazard. In laboratories, accepted practice is to have 1 sink in a room fitted with an eyewash on the counter adjacent to the sink. The sink cold-water supply provides water to the unit. The eye-wash could be designed to swing out of the way of the sink if desired.

Visibility of DevicesHigh visibility must be considered in the selection of any device. The recognition methods usually selected are high-visibility signs mounted at or on the device; having the surrounding floors and walls painted a con-trasting, bright color; and having the device in a bright, well lit area on the plant floor to help a victim identify the area and help in first-aid activities.

Number of StationsThe number of drench-equipment devices provided in a facility is a function of the number of people in rooms and areas with potential exposure to any par-ticular hazard at any one time, based on a worst-case scenario. It is rare for more than one combination unit to be installed. It is important to consider if a group of individuals has potential exposure to a specific hazard, more than one drench unit may be required. Consulting with the end user and the safety officer will provide a good basis for the selection of the type and number of equipment.

Generally, one shower can be provided between an adjacent pair of laboratories, with emergency eye/face washes located inside each individual laboratory. In open areas, it is common practice to locate emergency equipment adjacent to columns for support.

Water TemperatureCode now requires tempered water of approximately 85°F be supplied to equipment. A comfortable range of 60 to 95°F (15 to 35°C) is mentioned in the code. For most indoor applica-tions, this temperature range is achieved because the interior of a facility is heated in the winter and cooled in the summer to approximately 70°F (20° C). Since the water in the emergency drench system is stagnant, it assumes the temperature of the ambient air. A generally accepted temperature of between 80 and 85°F (27 and 30°C) has been established as a “comfort zone” and is now the recommended water temperature.

The body will attempt to generate body heat lost if the drenching fluid is at a temperature below the comfort zone. The common effect is shivering and increased heart rate. In fact, most individuals are uncomfortable taking a shower with water at about 60°F (15°C). With the trauma induced by an accident, the effect is escalated.

Another consideration is the potential chemical reaction and/or acceleration of reaction with flushing water or water at

Figure 4 Wheelchair-Accessible Shower and Eyewash Equipment




a particular temperature. Where the hazard is a solid, such as radioactive particles, that can enter the body through the pores, a cold-water shower shall be used in spite of its being uncom-fortable. It is necessary to obtain the opinions of medical and hygiene personnel where any doubt exists about the correct use of water or water temperature in specific facilities.

Where showers are installed outdoors, or indoors where heat-ing is not provided, the water supplying the showers must be tempered if the air temperature is low. Manufacturers offer a variety of tempering methods, including water-temperature maintenance cable similar to that used for domestic hot-water systems for this purpose and mixing valves with hot and cold-water connections. In remote locations, complete self-contained units are available with storage tanks holding and maintaining heated water.

Protection Against Temperature ExtremesIn areas where freezing is possible and water drench equipment is connected to an above-ground, plumbed water supply, freeze protection is required. This is most often accomplished by using electric heating cable and providing insulation around the entire water-supply pipe and the unit itself. It is recommended the water temperature be maintained at 85°F (20°C).

For exterior showers located where freezing is possible, the water supply shall be installed below the frost line and a freeze-proof shower shall be installed. This type of shower has a method of draining the water above the frost line when the water to the drench equipment is turned off.

When a number of drench-equipment devices are located where low temperature is common, a circulating tempered-water supply should be considered. This uses a water heater and a circulating pump to supply the drench equipment. The heater shall be capable of gen-erating water from 40 to 80°F at a rate of 30 gpm (or more if more than one shower could oper-ate simultaneously).

In areas where the temperature may get too high, it is accepted practice to insulate the water-supply piping.

BrEathIng-aIr SyStEmS

gEnEralBreathing-air systems supply air of a specific minimum purity to personnel for purposes of escape and protection after exposure to a toxic environment resulting from an acci-dent or during normal work where conditions make breathing the ambient air dangerous. As defined by 30 CFR 10, a toxic environment has air that “may produce physical discomfort immediately, chronic poisoning after repeated exposure, or acute adverse physiological symp-toms after prolonged exposure.”

This section discusses the production, puri-fication, and distribution of a low-pressure breathing air and individual breathing devices used to provide personnel protection only when used with supplied air systems. Low pres-sure for breathing air refers to compressed air pressures up to 250 psig (1725 kPa) delivered to

the respirator. The most common operating range for systems is between 90 and 110 psig (620 and 760 kPa).

Much of the equipment used in the generation, treatment, and distribution of compressed air for breathing-air systems is common to that for medical/surgical air discussed in the “Com-pressed-Gas Systems” chapter.

codES and StandardS1. OSHA: 29 CFR 1910.2. CGA: commodity specifications G-7 and G-7.1.3. Canadian Standards Association (CSA).4. National Institute of Occupational Safety and Health

(NIOSH).5. Mine Safety and Health Act (MSHA).6. NFPA: NFPA-99, Medical Compressed Air.7. DOD (Department of Defense): Where applicable.8. ANSI: Z-88.2, Standard for Respiratory Protection.9. Code of Federal Regulations (CFR).

BrEathIng-aIr purItyAir for breathing purposes supplied from a compressor or a pressurized tank must comply, as a minimum, with quality verification level grade D in CGA G-7.1 (ANSI Z-86.1). Table 1, from ANSI/CGA G-7.1, lists the maximum contaminant levels for various grades of air.

For grade D quality air, individual limits exist for condensed hydrocarbons, carbon monoxide, and carbon dioxide. Particu-

Table 1 Maximum Contaminant Levels for Various Grades of Air (in ppm [mole / mole] unless shown otherwise)

Limiting Characteristics A K L D E G J M N

Percent O2 balance predominantly N2

a

atm / 19.5 - 23.5

atm / 19.5 - 23.5

atm / 19.5 - 23.5

atm / 19.5 - 23.5

atm / 20 - 22

atm / 19.5 - 23.5

atm / 19.5 - 23.5

atm / 19.5 - 23.5

atm / 19.5 - 23.5

Water, ppm (v / v)b 200 50 1 3Dew point, °F b -33 -54 -104 -92Oil (condensed) (mg / m3 at NTP) 5c 5c Noned

Carbon monoxid 10e,f 10 5 1 1 10Odor NoneCarbon dioxide 1000f 500 500 0.5 1 500Total hydrocarbon content (as methane) 25 25 15 0.5 1Nitrogen dioxide Nitric oxide

2.5 0.1 0.5 2.5

Sulfur dioxide 2.5 0.1 5Halogenated Solvents 10 0.1Acetylene 0.05Nitrous oxide 0.1USP Yes

Source: ANSI / CGA G-7.1.ANSI 2-86.1, Table 1.Note: The 1973 edition of CGA G-7.1 listed nine quality verification levels of gaseous air, lettered A to J, and two quality verification levels of liquid air, lettered A and B. Some of those letter designations were dropped from the 1989 edition, since they no longer represent major volume usage by industry. Four new letter designations, K, L, M, and N, have been added to reflect current specifications. To get a listing of quality verification levels dropped, see CGA-7-1-1973 or contact the Compressed Gas Association.a The term atmospheric (atm) denotes the oxygen content normally present in atmospheric air; the numerical values denote the oxygen

limits for synthesized air.b The water content of compressed air required for any particular quality verification level may vary with the intended use from saturated

to very dry. For breathing air used in conjunction with a self-contained breathing apparatus in extreme cold where moisture can condense and freeze, causing the breathing apparatus to malfunction, a dew point not to exceen -50°F (63 ppm v / v), or 10° lower than the coldest temperature expected in the area, is required. If a specific water limit is required, it should be specified as a limiting concentration in ppm (v / v) or dew point. Dew point is expressed in °F at 1 atmosphere pressure absolute, 101 kPa abs. (760 mm Hg).

c Not required for synthesized air whose oxygen and nitrogen components are produced by air liquefaction.d Includes water.e Not required for synthesized air when the nitrogen component was previously analyzed and meets National Formulary (NF) specification.f Not required for synthesized air when the oxygen component was produced by air liquefaction and meets United States Pharmacopeia

(USP) specification.



lates and water vapor, whose allowable quantities have not been established, must also be controlled because of the effects they may have on different devices of the purification system, on the piping system, and on the end user of the equipment.

ContaminantsCondensed Hydrocarbons Oil is a major contaminant in breathing air. It causes breathing discomfort, nausea, and, in extreme cases, pneumonia. It can also create an unpleasant taste and odor and interfere with an individual’s desire to work. In addition, the oxidation of oil in overheated compressors can produce carbon monoxide. A limit of 5 ppm has been estab-lished.

Some types of reciprocating and rotary-screw compressors put oil into the airstream as a result of their operating character-istics. Accepted practice is to use only oil-free air compressors in order to eliminate the possibility of introducing oil into the airstream.

Carbon Monoxide Carbon monoxide is the most toxic of the common contaminants. It enters the breathing-air system through the compressor intake or is produced by the oxidation of heated oil in the compressor. Carbon monoxide easily com-bines with the hemoglobin in red blood cells, replacing oxygen. The lack of oxygen causes dizziness, loss of motor control, and loss of consciousness. A limit of 10 ppm in the airstream has been established based on NIOSH standards.

Carbon Dioxide Carbon dioxide is not considered one of the more dangerous contaminants. Although the lungs have a concentration of approximately 50,000 ppm, a limit of 1,000 ppm has been established for the breathing airstream.

Water and Water Vapor Water vapor enters the piping system through the air compressor intake. Since no upper or lower limits have been established by code, the allowable con-centration is governed by specific operating requirements of the most demanding device in the system, which is usually the CO converter, or the requirement of being 10°F lower than the lowest possible temperature the piping may experience.

After compression, water vapor is detrimental to the media used to remove CO. The dew point of the airstream must be greatly lowered at this point in order to provide the highest effi-ciency possible for this device. Water vapor is removed to such a low level that breathing air with this level of humidity will prove uncomfortable to users.

After purification, too much humidity will fog the faceplate of a full face mask. It will also cause freeze-up in the pipeline if the moisture content of the airstream in the pipe has a dew point that is higher than the ambient temperature of the area where the compressed-air line is installed.

Solid Particles Solid particles known as “particulates” can enter the system through the intake. They are released from non-lubricated compressors as a result of friction from carbon and Teflon material used in place of lube oils. No limits on par-ticulates have been established by code.

Odor There is no standard for odor measurement. A gener-ally accepted requirement is that there be no detectable odor in the breathing air delivered to the user. This requirement is sub-jective and will vary with individual users.

typES of SyStEmThere are three basic types of breathing-air system: constant flow, demand flow, and pressure demand.

Constant-Flow SystemAlso known as a “continuous-flow system,” the constant-flow system provides a continuous flow of purified air through per-sonnel respirators to minimize the leakage of contaminants into the respirator and to ventilate the respirator with cool or warm air depending on conditions.

This system could be used in a wide variety of areas, ranging from least harmful to most toxic, depending on the type of res-pirator selected.

Demand-Flow SystemThe demand-flow system delivers purified air to personnel res-pirators only as the individual inhales. Upon exhalation, the flow of air is shut off until the next breath. Demand-flow systems automatically adjust to an individual’s breathing rate.

This system requires tight-fitting respirators. Its application is generally limited to less harmful areas because the negative pressure in the respirator during inhalation may permit leakage of external contaminants. This system is designed for economy of air use during relatively short-duration tasks and is usually supplied from cylinders.

Pressure-Demand SystemA pressure-demand system delivers purified air continuously through personnel respirators with increased air flow during inhalation. By continuously providing a flow of air above atmo-spheric pressure, leakage of external contaminants is mini-mized.

This system also uses tight-fitting respirators, but the positive pressure aspect allows them to be used in more toxic applica-tions.

SyStEm componEntSThe breathing-air system consists of a compressed-air source, purification devices and filters to remove unwanted contami-nants from the source airstream, humidifiers to introduce water vapor into the breathing air, the piping distribution network, respirator outlet manifolds, respirator hose, and the individual respirators used by personnel. Alarms are needed to monitor the quantity of contaminants and other parameters of the system as a whole and to notify personnel if necessary.

Compressed-Air SourceThe source of air for the breathing-air system is an air compres-sor and/or high-pressure air stored in cylinders. Cylinders use ambient air, which is purified to reduce or eliminate impurities to the required level, and compress it to the desired pressure. A typical schematic detail is shown in Figure 5.

Air Compressor The standard for air compressors used to supply breathing air shall comply with the requirement for oil-free medical gas discussed in the “Compressed-Gas Systems” chapter. Medical-gas type compressors are used because these systems as a whole generate far fewer contaminants than other types of system. When a liquid-ring compressor is used, it has the advantage of keeping the temperature of the air leaving the unit low. It is also possible to use any type of compressor for this service, provided the purification system is capable of produc-ing air meeting all the requirements of code.

The air-compressor assembly consists of the intake assem-bly (including the inlet filter), the compressor and receiver, the aftercooler, and the interconnecting water-seal supply and the other ancillary piping. All of these components are discussed in the “Specialty Gases for Laboratories” section.




Air compressors have a high first cost and are selected if the use of air for breathing is constant and continuous, making the use of cylinders either too costly or too maintenance intensive because of the frequent changing of cylinders.

Storage Cylinder When high-pressure cylinders are used either as a source or as an emergency supply of breathing air, they shall be filled with air conforming to breathing-air stan-dards. The regulator should be set to about 50 psi (340 kPa) depending on the pressure required to meet system demands and losses.

The cylinders have a low initial cost and are not practical to use if there is continuous demand. Cylinders are best suited to intermittent use for short periods of time or as an emergency escape backup for a compressor.

AftercoolerSome components of the purification system require a specific temperature in order to function properly. Depending on the type of compressor selected and the type of purification nec-essary, the temperature of the air leaving the compressor may have to be reduced. This is done with an aftercooler.

Aftercoolers can be supplied with cooling water or use air as the cooling medium. Water, if recirculated, is the preferred method. The manufacturer of both the compressor and purifi-cation system should be consulted as to the criteria used and the recommended size of the unit.

Purification DevicesThe contaminants that are problematic for breathing-air systems must be removed. This can be done with separate devices used to remove individual contaminants or with a prepiped assem-bly of all the necessary purification devices, commonly referred to as a “purification system,” which requires only an inlet and

outlet air connection. For breathing-air systems it is commonly done with a purification system.

The individual purification methods used to remove specific contaminants are the same as those discussed in the “Com-pressed-Gas Systems” chapter. For breathing air, oil and par-ticulates are removed by coalescing and other filters, water is removed by desiccant or refrigerated dryers, and carbon mon-oxide is removed by chemical conversion to carbon dioxide using a catalytic converter.

Carbon Monoxide Converter The purpose of the converter is to oxidize carbon monoxide and convert it into carbon diox-ide, which is tolerable in much greater quantities. This is typi-cally accomplished by the use of a catalyst usually consisting of manganese dioxide, copper oxide, cobalt, and silver oxide in various combinations and placed inside a single cartridge. The material is not consumed but does become contaminated. The conversion rate greatly decreases if any oil or moisture is present in the airstream. Therefore, moisture must be removed before air enters the converter. Catalyst replacement is recommended generally once a year since it is not possible to completely con-trol all contaminants that contribute to decreased conversion.

Moisture Separator Water and water vapor are removed by two methods, desiccant and refrigerated dryers. The most common desiccant drying medium is activated alumina. For a discussion of air-drying methods, refer to the “Compressed-Gas Systems” systems.

Odor Remover Activated, granular charcoal in cartridges is used for the removal of odors.

Particulates Remover Particulates are removed by means of in-line filters. Generally accepted practice eliminates particu-lates 1 µ and larger from the piping system .

Figure 5 System with Standby High-Pressure Breathing Air Reserve

Sour

ce: C

ourte

sy of

Nom

onox

.



HumidifierWhen water is removed from the compressed airstream prior to catalytic conversion, the dryer produces very dry air. If the breathing-air system is intended to be used for long periods of time, very low humidity will dry the mucous membranes of the eyes and mouth. Therefore, moisture must be added to the airstream to maintain recommended levels. Humidifiers, often called “moisturizers,” are devices that inject the proper level of water vapor into an airstream. Some require a water connec-tion.

A recommended level of moisture is 50% relative humidity in the compressed airstream. Care must be taken not to route the air-distribution piping through areas capable of having tem-peratures low enough to cause condensation. If the routing is impossible to change, a worker will have shorter periods of time on the respirator.

Combination Respirator Manifold and Pressure ReducerThis is a single component with multiple quick-disconnect out-lets providing a convenient place both to reduce the pressure of the distribution network and to serve as a connection point for several hoses. A pressure gauge should be installed on the man-ifold to ensure the outlet pressure is within the limits required by the respirator.

Respirator HoseThe respirator hose is flexible and is used to connect the res-pirator worn by an individual to the central-distribution piping system. Code allows a maximum hose length of 300 ft (93 m)

Personnel RespiratorsThere are two general categories of respirator used for individual protection: air purifying and supplied air.

The air-purifying type of respirator is portable and has self-contained filters that purify the ambient air on a demand basis. The advantages to its use are that it is less restrictive to move-ments and is light in weight. Disadvantages are that it must not be used where gas or vapor contamination cannot be detected by odor or taste and in an oxygen-deficient atmosphere. This type of respirator is outside the scope of this book, it is men-tioned only because of its availability.

The type of respirator selected depends on the expected breathing hazards. In the choice of a respirator, the highest expected degree of hazard, applicable codes and standards, manufacturer recommendations, suitability for the intended task and the comfort of the user are all important consider-ations.

The EPA Office of Emergency and Remedial Response has identified four levels of hazard at cleanup sites involving haz-ardous materials and lists guidelines for the selection of protec-tive equipment for each:1. Level A calls for maximum available protection, requiring a

positive-pressure, self-contained suit, generally with a self-contained breathing apparatus worn inside the protective suit.

2. Level B protection is required when the highest level of respiratory protection is needed but a lower level of skin protection is acceptable.

3. Level C protection uses a full face piece and air-purifying respiratory protection with chemical resistant, disposal garments. This is required when the contaminant is known and the level is relatively constant. Typical of its uses is for asbestos removal.

4. Level D protection is used where special respiratory or skin protection is not required but a rapid increase of contami-nant level or degradation of ambient oxygen content is pos-sible.

If the hazard cannot be identified, it must be considered an immediate danger to life and health (IDLH). This is a condition that exists when the oxygen content falls below 12.5% (95 ppm O2) or where the air pressure is less than 8.6 psi (450 mm/Hg), which is the equivalent of 14,000 ft (4270 m).

There are five general types of respirator available, as follows:Mouthpiece Respirators Used only with demand type

systems, mouthpiece respirators are designed only to deliver breathable air. They offer no protection to the skin, eyes, or face. Their use is limited to areas where there is insufficient oxygen and no other contaminants could affect the eyes and skin.

Half-Face-Piece Respirators Half-face-piece respira-tors cover the nose and mouth and are designed primarily for demand and pressure type systems. They are usually tightfitting and provide protection for extended periods of time in atmo-spheres that are not harmful to the eyes and skin. Often worn with goggles, these respirators are limited to areas of relatively low toxicity.

Full-Face-Piece Respirators Full-face-piece respirators cover the entire face and are designed for use with constant-flow and pressure-demand systems. They are tightfitting and suitable for atmospheres of moderate and high toxicity. They are usually used in conjunction with full protective clothing for such tasks as chemical-tank cleaning where corrosive and toxic gas, mist, and liquids may be present. Since the face masks provide pro-tection to the face and eyes, they are also suitable for other tasks, such as welding and the inspection of tanks and vessels where there is an oxygen-deficient atmosphere.

Hood-and-Helmet Respirators Hood-and-helmet respira-tors cover the entire head and are normally used with a con-stant-flow system. They are loose fitting and suitable only for protection against contaminants such as dust, sand, powders, and grit. Constant flow is necessary to ventilate the headpiece and to provide sufficient air pressure to prevent contaminants from entering the headpiece.

Full-Pressure Suits Full-pressure suits range in design from loose-fitting, body-protective clothing to completely sealed, astronaut-like suits that provide total environmental life sup-port. They are designed to be used only with constant-flow sys-tems and are suitable for the most toxic and dangerous environ-ments and atmospheres.

componEnt SElEctIon and SIzIng

Breathing-Air SourceAir Compressor The air-compressor size is based on the high-est flow rate, in cfm (L/min), required by the number and type of respirators intended to be used simultaneously and the mini-mum pressure required by the purification system.

The following general flow rates are provided as a prelimi-nary estimate for various types of respirator. Since there is a wide variation in the pressure and flow rates required for vari-ous types of respirator, the actual figures used to size the system must be based on the manufacturer’s recommendations for the specific respirators selected.1. 4 scfm (113 L/min) for pressure-demand respirators.2. 6 scfm (170 L/min) for constant-flow respirators.




3. Up to 16 scfm (453 L/min) for flooded-hood respirators.4. Up to 35 scfm (990 L/min) for flooded suits.5. Add 15 scfm (425 L/min) of air for suit cooling if used.

High-Pressure Storage Cylinder High pressure cylinders are used either to supply air for normal operation to a limited number of personnel for short periods of time or as an emer-gency supply to provide a means of escape from a hazardous area if the air compressor fails. The main advantage to using cylinders is the air in the cylinders is prepurified, and no further purification of the air is necessary.

The number of cylinders is based on the simultaneous use of respirators, the cfm (L/min) of each and the duration, in min, the respirators are expected to be used, plus a 10% safety factor. The total amount of compressed air in the cylinders should not be allowed to decrease too low. A low-pressure alarm should sound when pressure falls to 500 psig (3450 kPa) in a cylinder normally pressurized to 2400 psig (16 500 kPa) when filled to capacity.

Example 9-1Establish the number of cylinders required for an emergency supply of air for 8 people using constant-flow respirators require 15 min to escape the area.1. 8 × 6 × 15 = 720 scfm + 72 (10%) = 792 scfm total required2. Next, find the actual capacity of a single cylinder at the

selected high pressure, generally 2400 psi (16 500 kPa), and divide the capacity of each cylinder into the total scfm required to find the number of cylinders required.

3. If 1 cylinder has 225 scf, 792 ÷ 225 = 3.5. Use 4 cylinders.

Purification ComponentsThe air used to fill breathing-air cylinders is purified before being compressed. Breathing air produced by air compressors requires purification to meet minimum code standards for breathing air.

Prior to the selection of the purification equipment, several samples of the air where the compressor intake is to be located should be taken so specific contaminants and their amounts can be identified. The ideal situation is to have the tests taken at different times of the year and different times of the day. These tests quantify the type and amount of contaminants present at the intake. With this information known, the purification sys-tems needed to meet code criteria can be chosen. The other requirement is the highest flow rate that can be expected. With these criteria, the appropriate size and types of purifier can be selected.

The most commonly used method of purification is an assem-bly of devices called a “purification system” specifically chosen and based on the previously selected criteria. Manufacturers’ recommendations are commonly followed in the selection and sizing of the assembly.

Carbon-Monoxide Converter The requirement for installa-tion of a carbon-monoxide converter is rare. The need for a con-verter is based on tests of the air at the proposed location of the compressor intake. Another source of information is the EPA, which has conducted tests in many urban areas throughout the country. Another indication that installation may be necessary is the use of a non-oil-free compressor. Good practice requires the installation of a converter if there is an outside chance the level of carbon monoxide may rise above the 10 ppm limit set by code.

The converter is sized based on the flow rate of the system.Coalescing Filter/Separator The coalescing filter/separa-

tor is a single unit that removes large oil and water drops and particulates from the airstream before the air enters the rest of the system. It is selected on the basis of maximum system pres-sure, flow rate, and the expected level of contaminants leaving the air compressor, using manufacturer’s recommendations. If an oil-free compressor is used, a simple particulate filter could be substituted for the coalescing filter.

Dryers (Moisture Separators)Desiccant Dryers — The two types of desiccant media dryer most commonly used are the single-bed dryer, which is a disposable cartridge, and the continuous-duty, two-bed dryer.

When two-bed dryers are used, a portion of the air from the compressor is used for drying one bed while the other is in ser-vice. The compressor must be capable of producing enough air for both the system and dryer use.

The single-bed dryer has a lower first cost but a higher operat-ing cost. The disposable cartridge often is combined with other purification devices into a single, prepiped unit. An indicator is often added to the media so the need for replacement is indi-cated by a color change.

Disposable units are best suited for short durations or occa-sional use, such as for replacement of a main unit during peri-ods of routine service. Because of their generally small size, only a limited number of respirators can be supplied from a single unit. Other considerations are that these disposable units have a limited capacity, in total cfh, they can process. Manufacturers’ recommendations must be used in the selection of the size and number of replacement cartridges required for any application.

The two-bed unit, commonly called a “heatless dryer,” is simi-lar in principle to that discussed in the “Compressed-Gas Sys-tems” chapter. Such units are used for continuous duty.

The two factors contributing to the breakdown of media are fast-drying cycles and high air velocity. If a desiccant dryer is selected, the velocity of air through the unit shall conform to manufacturer’s recommendations. Velocity should be as low as is practical to avoid fluidizing the bed. High velocity requires more cycles for drying, which means wasting more air. If the size of the dryer is a concern, more drying cycles means smaller dryer beds. Longer drying cycles reduce component wear.

Refrigerated Dryers — Refrigerated dryers are used if there is no requirement for a nitrous oxide converter and if the 35–39°F dew point produced is 10°F below the lowest ambient air tem-perature where any pipe will be installed. The refrigerated dryer is less efficient than the desiccant dryer. Its advantages are that all the air produced by the compressor is available to the system and it has a lower pressure loss.

When refrigerated dryers are preferred, several purification devices are often combined into a single unit, including the refrigeration unit, filter/separator for oil and water, and a char-coal filter for odor removal. This unit produces air that is lower in temperature than the inlet air.

If the breathing-air distribution piping is to be routed through an area of lower temperature, the pressure dew point of the air must be reduced to 10°F lower than the lowest temperature expected.

Odor Remover Odors are not usually a problem, but their removal is provided for as a safeguard. The activated charcoal cartridges remove odors are selected using manufacturers’ rec-



ommendations based on the maximum calculated flow rate of the breathing-air system. The cartridges must be replaced peri-odically.

HumidifiersOften called a “moisturizer,” a humidifier is required to increase the relative humidity of the breathing air to approximately 50% if required. The unit is selected using the increase in moisture required for the airstream and the flow rate of air. Caution must be used so as not to increase the dew point of the compressed air above a temperature 10°F lower than the lowest temperature in any part of the facility the pipe is routed through.

Respirator HoseThe respirator hose most often used to connect the respirator worn by an individual to the central-distribution piping system is 3⁄8 in. (10 mm) in size. Code allows a maximum hose length of 300 ft (93 m). The most common lengths are between 25 and 50 ft (7.75 and 15.5 m).

System Sizing CriteriaSystem Pressure The outlet pressure of the compressor shall be within the range required by the purification system. Typi-cally, the pressure is approximately 100 psi (70.3 kg/cm2). The precise range of pressure and flow rate shall be obtained from the purification system manufacturer selected for the project.

The pressure in the distribution system should be as high as possible to reduce the size of the distribution-piping network. Code requires the pressure be kept below 125 psi (88 kg/cm2). The distribution-piping pressure range is usually 90 to 110 psig (620 to 760 kPa) available in the system after the purifier.

The pressure required at the respirator ranges from approxi-mately 15 psig for pressure-demand respirators to 80 psig for full-flooded suits that require cooling. The actual requirements can be obtained only from the manufacturer of the proposed equipment because of the wide variations possible. Pressure-regulating valves shall be installed to reduce the pressure to the range acceptable to the respirator used. Often, this reduction is done at the respirator manifold, if one is used, or, if a single respirator type with a single pressure is used throughout the facility, a single regulator can be installed to reduce the pressure centrally.

Pipe Sizing and Materials The most commonly used pipe is type L copper tubing, with wrought copper fittings and brazed joints.

For pipe sizing, follow the sizing procedure discussed in the “Compressed-Gas Systems” chapter. The number of simultane-ous users must be obtained from the facility. No diversity factor should be used.

Alarms and MonitorsThe following alarms and monitors are often provided:

CO Monitor Usually included as a built-in component, this monitor measures the CO content of the airstream and sounds an alarm when the level reaches a predetermined high set point.

Oxygen-Deficiency Monitor Used as a precautionary mea-sure in an area where respirators are not normally required, the oxygen monitor measures the oxygen content of the air in a room or other enclosed area and sounds an alarm to alert per-sonnel when the level falls below a predetermined level. Usu-ally, several alarm points are annunciated prior to reaching a level low enough to require the use of respirators.

Low-Air-Pressure Monitor The low-air-pressure monitor must sound an alarm when the pressure in the system reaches a predetermined low point. This set point allows the users of the breathing-air system to leave the area immediately while still being able to breathe from the system. For cylinder storage, this set point is about 500 psig in the cylinders. For a compres-sor system, the alarm should sound when the pressure falls to a point 10 psig below the pressure set to start the compressor. This should also switch over to the emergency backup supply if one is used. If no backup is used, the pressure set point shall be 5 psig higher than the minimum required by the respirators being used.

Dew-Point Monitor A dew-point monitor is used to mea-sure the dew point and sound an alarm if it falls to a low point, set by a health officer, that might prove harmful to the users. It is required to alarm if the dew point reaches a point high enough to freeze in some parts of the system.

High-Temperature Air Monitor Some purifiers or purifier components will not function properly if the inlet air tempera-ture is too high. The set point is commonly 120° F but will vary among different manufacturers and components.

Failure-to-Shift Monitor This monitor is placed on des-iccant dryers to initiate an alarm if the unit fails to shift from the saturated dryer bed to the dry bed when regeneration is required.





PSD

134


CE Questions—“Life-Safety Systems” (PSD 134)

About This Issue’s ArticleThe July/August 2006 continuing education article is

“Life-Safety Systems,” Chapter 8 of Pharmaceutical Facilities Plumbing Systems by Michael Frankel. This chapter describes water-based emergency drench equipment and systems commonly used as a first-aid measure to mitigate the effects of such an accident. Also described are the breathing-air systems that supply air to personnel for escape and protec-tion when they are exposed to either a toxic environment resulting from an accident or normal working conditions that make breathing the ambient air hazardous.

You may locate this article at www.psdmagazine.org. Read it, take the following exam, and submit it to the ASPE office to potentially receive 0.1 CEU (comparable to 1.0 PDH).

1. The recommended supply pipe size to an emergency shower is ________.a. ¾ inch, b. 1 inch, c. 1¼ inches, d. 1½ inches

. Since oil is a major contaminant in breathing air systems, the maximum allowed is ___________.a. 5 ppm, b. 5 ppb, c. 10 ppm, d. 10 ppb

. An emergency shower drench hose is used to _________.a. wash the floor after a chemical spillb. irrigate the body under the clothing prior to removal of

the clothingc. provide a means to fill mop bucketd. none of the above

. A failure-to-shift monitor is ___________.a. used to control multi-stage compressorsb. used to initiate an alarm if a desiccant dryer fails to

shift from the saturated bed to the dry bed when regeneration is required

c. used to coordinate the output signal of the low air pressure monitor and the refrigerated dryer

d. not required on modern systems

. In areas where strong acid or caustic is used, the emergency shower and eyewash equipment should be located within ___________ feet of the potential source of the hazard per ANSI code Z-.1.a. 5, b. 10, c. 15, d. 20

. What is the established comfort zone water temperature for emergency drench equipment?a. 70–75°F, b. 75–80°F, c. 80–85°F, d. 85–90°F

. As defined by “0 CFR 10,” a toxic environment has air that ___________.a. may produce physical discomfort immediatelyb. may cause chronic poisoning after repeated exposurec. may cause acute adverse physiological symptoms after

prolonged exposured. all of the above

. The code-required flow rate from an emergency shower is ___________ gpm.a. 25, b. 30, c. 35, d. 40

. How many cylinders of air are required for an emergency supply of air for eight people using pressure demand respirators needing 1 minutes to escape the area?a. 2.3 use 3 cylindersb. 3.5 use 4 cylindersc. 4.7 use 5 cylindersd. cannot be determined

10. Refrigerated dryers are used ___________.a. when money is of no concernb. when order removal is not requiredc. when system pressure is high enough to accommodate

themd. none of the above

11. The minimum diameter of the spray pattern from an emergency shower, measured at 0 inches above the surface on which the user stands, is ___________ inches.a. 18, b. 20, c. 22, d. 24

1. An oxygen content below 1. percent and/or a pressure of . psi should be considered ___________.a. as a Level A hazard as established by the EPAb. as a Level C hazard as established by the EPAc. as a Level E hazard as established by the EPAd. as an immediate danger to life and health


Now Online!Starting with this issue, the technical article you must read to com-

plete the exam will be located at www.psdmagazine.org. The following exam and application form also may be downloaded from the Web site. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. For most people, this process will require approxi-mately one hour. If you earn a grade of 90 percent or higher on the test, you will be notified that you have logged 0.1 CEU, which can be applied toward the CPD renewal requirement or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for three years.






1. Photocopy this form or download it from www.psdmagazine.org.2. Print or type your name and address. Be sure to place your ASPE membership number in the appropriate space.3. Answer the multiple-choice continuing education (CE) questions based on the corresponding article found on

www.psdmagazine.org and the appraisal questions on this form.4. Submit this form with payment ($35 for nonmembers of ASPE) if required by check or money order made payable to ASPE or



Name __________________________________________________________________________________________________


Organization ____________________________________________________________________________________________

Billing Address ___________________________________________________________________________________________


Country ___________________________________________ E-mail ________________________________________________


PS&D Continuing Education Answer SheetLife-Safety Systems (PSD 134)


Appraisal QuestionsLife-Safety Systems (PSD 134)






Signature

Expiration date: Continuing education credit will be givenfor this examination through July 1, 00.Applications received after that date will not be processed.








PSD

131

Medical Gas and Vacuum Systems



PSDMAGAZINE.ORG


GENErAlHealth care is in a constant state of change, which forces theplumbing engineer to keep up with new technology to provideinnovative approaches to the design of medical-gas systems. Indesigningmedical-gasandvacuumsystems,thegoalistoprovideasafeandsufficientflowatrequiredpressurestothemedical-gasoutletorinletterminalsserved.Systemdesignandlayoutshouldallowconvenientaccessbythemedicalstafftooutlet/inlettermi-nals,valves,andequipmentduringpatientcareoremergencies.

This section focuses on design parameters and current stan-dardsrequiredforthedesignofnonflammablemedical-gasandvacuum systems used in therapeutic and anesthetic care. Theplumbingengineermustdeterminetheneedsofthehealth-carestaff.Trytoworkcloselywiththemedicalstafftoseekanswerstothefollowingfundamentaldesignquestionsatthestartofaproj-ect:1. Howmanyoutlet/inletsarerequestedbystaff?

2. Howmanyoutlet/inletsarerequired?

3. Basedoncurrentconditions,howoftenistheoutlet/inletused?

4. Basedoncurrentconditions,whatistheaveragedurationofuseforeachoutlet/inlet?

5. Whatistheproperusage(diversity)factortobeused?

MEDICAl-GASSySTEMDESIGNChECklISTAs any hospital facility must be specially designed to meet theapplicablelocalcoderequirementsandthehealth-careneedsofthecommunityitserves,themedical-gasandvacuumpipingsys-temsmustalsobedesignedtomeetthespecificrequirementsofeachhospital.

Followingare theessentialsteps toawell-designedandfunc-tionalmedical-gaspipedsystem,whicharerecommendedtotheplumbingengineer:1. Analyzeeachspecificareaofthehealth-carefacilitytodeter-

minethefollowingitems:A. Whichpipedmedical-gassystemsarerequired?B. Howmanyofeachdifferenttypeofmedical-gasoutlet/inlet

terminalarerequired?C. Whereshouldtheoutlet/inletterminalsbelocatedfor

maximumefficiencyandconvenience?D. Whichtypeandstyleofoutlet/inletterminalbestmeetthe

needsofthemedicalstaff?2. Anticipateanybuildingexpansionandplaninwhichdirec-

tiontheexpansionwilltakeplace(verticallyorhorizontally).Determinehowthemedical-gassystemshouldbesizedandvalvedinordertoaccommodatethefutureexpansion.

3. Determinelocationsforthevariousmedical-gassupplysources.

A. Bulkoxygen(O2).B. High-pressurecylindermanifolds(O2,N2OorN2).C. Vacuumpumps(VAC).D. Medical-aircompressors(MA).

4. Preparetheschematicpipinglayoutlocatingthefollowing:

A. Zonevalves.B. Isolationvalves.C. Masteralarms.D. Areaalarms.

5. Calculatetheanticipatedpeakdemandsforeachmedical-gassystem.Appropriatelysizeeachparticularsectionso astoavoidexceedingthemaximumpressuredropsallowed.

6. Sizeandselectthevariousmedical-gasandvacuumsupplyequipmentthatwillhandlethepeakdemandsforeachsystem,includingfutureexpansions.Ifthisprojectisanaddi-tiontoanexistingfacility,determinethefollowing:

A. Whatmedicalgasesarecurrentlyprovidedandwhatarethelocationsandnumberofthestations?

B. Canthecurrentgassupplier(orthehospital’spurchasingdepartment)furnishtheconsumptionrecords?

C. Arethecapacitiesoftheexistingmedical-gassupplysys-temsadequatetohandletheadditionaldemand?

D. Areanyexistingsystemsvalvedthatcouldbeusedforanextension?Aretheexistingpipesizesadequatetohandletheanticipatedadditionalloads?

E. Whattypeofequipmentisinuseandwhoisthemanufac-turer?Isthisequipmentstate-of-the-art?

F. Isitfeasibletomanifoldthenewandexistingequipment?G. Whatisthephysicalconditionoftheexistingequipment?H. Isthereadequatespaceavailableforthenewmedical-gas

supplysystemsandrelatedequipmentattheexistingloca-tion?

I. Isexistingequipmentscheduledtobereplaced?(Amain-tenancehistoryoftheexistingequipmentmayhelpinthisdetermination.)

NuMBEroFSTATIoNSThefirststepistolocateandcounttheoutlet/inlets,oftencalled“stations,”foreachrespectivemedical-gassystem.Thisisusuallydonebyconsultingaprogrampreparedbythefacilityplannerorarchitect.Thisprogramisalistofalltheroomsandareasinthefacilityandtheservicesthatarerequiredineach.Ifaprogramhasnotbeenprepared,thefloorplansfortheproposedfacilityshallbeused.

There is no code that specifically mandates the exact numberofstationsthatmustbeprovidedinvariousareasorroomsforallhealth-carefacilities.Infact,thereisnoclearconsensusofopinionamongmedicalauthoritiesordesignprofessionalsastohowmanystationsareactuallyrequiredinthefacilityareas.Guidelinesare


Medical Gas andVacuum Systems

Reprinted from American Society of Plumbing Engineers Data Book Volume 3: Special Plumbing Systems, Chapter 2: “Medical Gas and Vacuum Systems.” ©2000, American Society of Plumbing Engineers.

PlumbingSystems&Design JANUARY/FEBRUARY 2006 PSDMAGAZINE.ORG


published by the American Institute of Architects(AIA),NationalFireProtectionAssociation(NFPA),and ASPE that recommend the minimum numberofstationsforvariousservicesinspecificareas.

The most often-used recommendations in deter-miningthenumberofstationsforhospitalsarethosenecessarytobeaccreditedbytheJointCommissionfor the Accreditation of Hospitals Organization(JCAHO).AccreditationisrequiredforMedicareandMedicaid compensation. The JCAHO publishes amanualthatreferstotheAIAguidelinesforthemini-mum number of stations for oxygen, medical air,andvacuumthatmustbeinstalledinordertoobtainaccreditation.If thisisafactorforthefacility,theserequirements are mandatory. Other jurisdictions,suchasstateorlocalauthorities,mayrequireplanstobeapprovedby localhealthorbuildingofficials.These approvals may require adhering to the stateorlocalrequirementsand/orNFPA99,Health-Care Facilities.

If accreditation or the approval of authorities isnota factor, thenumberandarealocationsofsta-tionsarenotmandated.Theactualcountthenwilldepend upon requirements determined by eachindividualfacilityoranothermemberofthedesignteam using both past experience and anticipatedfuture use, often using the guideline recommenda-tionsasastartingpoint.

MEDICAl-GASFlowrATESEachstationmustprovideaminimumflowratefortheproper functioning of connected equipment underdesignandemergencyconditions.Theflowratesanddiversity factors vary for individual stations in eachsystemdependingonthetotalnumberofoutletsandthetypeofcareprovided.

Theflowratefromthetotalnumberofoutlets,with-out regard for any diversity, is called the “total con-nectedload.”Ifthetotalconnectedloadwereusedforsizingpurposes,theresultwouldbeavastlyoversizedsystem,sincenotallofthestationsinthefacilitywillbe used at the same time. A diversity, or simultane-ous-usefactor,isusedtoallowforthefactthatnotallofthestationswillbeusedatonce.Itisusedtoreducethesystemflowrateinconjunctionwiththetotalcon-nectedloadforsizingmainsandbranchpipingtoallpartsofthedistributionsystem.Thisfactorvariesfordifferentareasthroughoutanyfacility.

Theestimatedflowrateanddiversityfactorsforvarioussystems,areastations,andpiecesofequipmentarefoundinTable1.

Total demand for medical-gas systems varies as a function oftimeofday,month,patient-carerequirements,andfacilitytype.Thenumberofstationsneededforpatientcareissubjectiveandcannot be qualified based on physical measurements. Knowingthetypesofpatientcareand/orauthorityrequirementswillallowplacementofstationsinusagegroups.Thesegroupscanestablishdemand and simultaneous-use factors (diversities), which areusedinthecalculationforsizingaparticularsystem.Allmedical-gaspipingsystemsmustbeclearlyidentifiedusinganapprovedcolor-codingsystemsimilartothatshowninTable2.

MEDICAl-GASSySTEMDISPENSINGEquIPMENTMedical-gas outlet/inlet terminals Most manufacturers of

medical-gas system equipment offer various types of medical-gasoutlets.Thesemedical-gasoutletsareavailableinvariousgasorders(e.g.,O2-N2O-Air),center-linespacing,andforexposedandconcealedmountings.Outlettypesandconfigurationsmustmeetthe requirements of the local jurisdictional authority and NFPA99. All outlets must be properly identified and confirmed. Careshouldalsobetakentoaccuratelycoordinatethevariouspiecesofmedical-gasdispensingequipmentwiththearchitectandmedicalstaffinvolvedinthegivenproject.Iftheprojectisarenovation,theoutlettypesshouldmatchexistingequipment.Withprefabricatedpatientheadwallunits,themedical-gasoutletsaregenerallyfur-nishedbytheequipmentmanufacturer,andit isveryimportantthatcoordinationbemaintainedbytheengineersothatunneces-

table 1 Outlet Rating Chart for Medical-Vacuum Piping Systems

Free-Air Allowance, cfm (L/min) at 1 atmosphere

Zone Allowances— Corridors, Risers, Main Supply Line,

Valves

Location of Medical-Surgical Vacuum Outlets Per Room Per Outlet

Simultaneous Usage Factor

(%)

Air to Be Transported, cfm (L/min)a

Operating rooms: Major “A” (Radical, open heart; organ

transplant; radical thoracic) 3.5 (100) — 100 3.5 (100) Major “B” (All other major ORs) 2.0 (60) — 100 2.0 (60) Minor 1.0 (30) — 100 1.0 (30)Delivery rooms 1.0 (30) — 100 1.0 (30)Recovery room (post anesthesia) and intensive-care units (a minimum of 2 outlets per bed in each such department): 1st outlet at each bed — 3 (85) 50 1.5 (40) 2nd outlet at each bed — 1.0 (30) 50 0.5 (15) 3rd outlet at each bed — 1.0 (30) 10 0.1 (3) All others at each bed — 1.0 (30) 10 0.1 (3)Emergency rooms — 1.0 (30) 100 1.0 (30)Patient rooms: Surgical — 1.0 (30) 50 0.5 (15) Medical — 1.0 (30) 10 0.1 (3) Nurseries — 1.0 (30) 10 0.1 (3)Treatment & examining rooms — 0.5 (15) 10 0.05 (1)Autopsy — 2.0 (60) 20 0.04 (1)Inhalation therapy, central supply & instructional areas — 1.0 (30) 10 0.1 (3)

a Free air at 1 atmosphere.

table 2 Color Coding for Piped Medical Gases

Gas Intended for Medical Use United States Color Canada ColorOxygen Green Green on whitea

Carbon dioxide Gray Black on grayNitrous oxide Blue Silver on blueCyclopropane Orange Silver on orangeHelium Brown Silver on brownNitrogen Black Silver on blackAir Yellow* White and black on black and whiteVacuum White Silver on yellowa

Gas mixtures (other than mixtures of oxygen and nitrogen)

Color marking of mixtures shall be a combination of color corresponding to each component gas.

Gas mixtures of oxygen and nitrogen

19.5 to 23.5% oxygenAll other oxygen concentrations

Yellowa

Black and greenBlack and whitePink

Source: Compressed Gas Association, Inc.a Historically, white has been used in the United States and yellow has been used in Canada to identify vacuum systems. Therefore, it is recommended that white not be used in the United States and yellow not be used in Canada as a marking to identify containers for use with any medical gas. Other countries may have differing specific requirements.

JANUARY/FEBRUARY 2006 PlumbingSystems&Design


CONTINUING EDUCATION: Medical Gas and vacuum Systemssaryduplicationofworkisavoided.Also,withregardtotheover-the-bed medical-gas service consoles, these consoles are oftenspecified in theelectricalorequipmentsectionof thespecifica-tionandmedical-gasserviceoutletsarespecified,furnished,andinstalledunderthemechanicalcontract.

Gas-outlet sequence, center-line spacing, and multiple-gang-service outlets are some of the considerations to be taken intoaccountwhenrequestinginformationfromthevariousequipmentmanufacturers.Itismorepractical,intermsofboththecostoftheequipmentandtheinstallation,tospecifyandselectthemanufac-turer’sstandardoutlet(s).Detailsandspecificationsregardingtheindividualstandardoutletsareusuallyavailablefromallmanufac-turersuponrequest.

Theexistingoutletsarecompatiblewiththeadaptersfoundonthehospital’sanesthesiamachines,flowmeters,vacuumregula-tors,etc.Careshouldbetakentomakesureallfutureexpansionsinthesamefacilityhavecompatibleequipment.

Patient head-wall systems A recent and growing trend inhospital construction is the requirement for patient head-wallsystems,which incorporate many services for thepatient’s care.Theseunitsmayincludethefollowing:1. Medical-gasoutlets.

2. Electrical-serviceoutlets(includingemergencypower).

3. Directandindirectlighting.

4. Nurse-callsystem.

5. Isolationtransformers.

6. Groundingoutlets.

7. Patient-monitoringreceptacles.

8. VacuumslideandIVbrackets.

9. Nightlights.

10.Electricalswitches.

Bed locator units are also available, which serve to providepowerforthemoreadvancedpatientbeds,telephone,nightlights,and standard power. These unitsalso function to protect the wallsfrom damage as beds are movedandadjusted.

Head walls currently vary inshape, size, type, and cost from asimple over-the-patient-bed stan-dard configuration to elaboratetotal-wallunits.Mostmanufactur-ersofmedical-gasequipmentoffermedical-gas outlets for all typesof patient consoles available intoday’s market. When specifyinghead-walls outlets, the plumbingengineer should consider the fol-lowing:1. Istheserviceoutletselected

compatiblewiththeexistingoutletcomponent?

2. Doesthepatienthead-wallmanufacturerincludethetypeofmedical-gasoutletsrequiredaspartoftheproduct?

Special types of ceiling-mounted, medical-gas out-

lets In critical-care areas, which are generally considered bymostindividualstobethoselocationsofthehospitalprovidingaspecialtreatmentorserviceforthepatient(suchassurgery,recov-ery,coronary,orintensive-careunits),thedesigner’sselectionandplacement of the medical-gas service equipment must be doneverycarefullyinordertoprovideefficientworkcentersaroundthepatientforthemedicalstaff.

Manufacturers of medical-gas service equipment usually pro-videawiderangeofequipmentthatisavailableforuseintheseareas.Dependinguponthecustomer’spreferenceandtheavail-ablebudget, theequipment isselectedtoprovidethenecessaryindividualgasservicesandaccessories.

Table3providesaquickreferenceguidefortheengineertouseasabasisforselectingthecommonlyusedtypesofoutletdispens-ingequipment.

Example 1The following illustrative example presents some of the most

importantcritical-careareaequipmentandoptionsfortheselec-tionoftheequipment.

Surgerymedical-gasservicestobepipedinclude:1. Oxygen.

2. Nitrousoxide.

3. Nitrogen.

4. Medicalcompressedair.

5. Vacuum.

6. Wasteanesthetic-gasdisposal.

Providingmedical-gasserviceoutletsinthesurgeryroommaybeaccomplishedinseveralways,suchasthefollowing:1. Ceiling outlets Individualmedical-gasoutletsmountedinthe

ceilingwithhoseassembliesprovidingthemedicalstaffwithconnectionsfromtheoutletstotheadministeringapparatus.

Thismethodisconsideredbymosttobethemosteconomi-calmeansofprovidinganadequategasservicetothesurgery

table 3 Types of Dispensing Equipment for Specific Areas

Hospital Areas

Medical Gas Outlet Dispensing Equipment

Wall-Mounted Outlets

Patient Care Head

Wall

Ceiling-Mounted

Outlets with Hose Stops

Rigid Ceiling

Columns

Retractable Ceiling

Columns

Ceiling with Gas

Stacks

Nitrogen Control

CabinetsAutopsy rooms • •Delivery rooms • •Emergency examination and treatment rooms

• •Emergency operating rooms • •Induction rooms •Labor rooms • •Major surgery rooms • • • • • •Minor surgery, cystoscopy • • •Neonatal intensive care units • •Normal nursery rooms • •Nursery workrooms •O.B. recovery rooms • •Patient rooms • •Pediatric and youth intensive care unit • • •Post-operative recovery rooms • • •Premature and pediatric nursery rooms • • •Pre-op holding rooms • •Radiology rooms •Respiratory care unit •Specialized surgeries (cardiac and neuro) • •



areas.Theceilinggas-serviceoutletsaregenerallylocatedatboththeheadandthefootoftheoperatingtableinordertoprovidealternatepositioningoftheoperatingtable.

2. Surgical ceiling columns Surgicalceilingcolumnsareusu-allyavailableintwodesigns:rigid(apredeterminedlengthfromtheceilingheightabovethefloor)andretractable.Bothsurgicalceilingcolumnsprovidemedical-gasserviceswithinanenclosurethatprojectsdownfromtheceiling.Theceilingcolumnsareusuallylocatedatoppositeendsoftheoperatingtableinordertoprovideconvenientaccesstothemedical-gasoutletsbytheanesthesiologist.Inadditiontothemedical-gasoutlets,theseceilingcolumnscanbeequippedwithelectri-caloutlets,groundingreceptacles,physiologicalmonitorreceptacles,andhooksforhangingintravenous-solutionbottles.

Mostmanufacturersofferingsurgicalceilingcolumnsallowformanyvariationsinroomarrangementsofmedical-gasservicesandrelatedaccessories,dependinguponthespecificcustomer’sneedsandtheengineer’sspecifications.Whenspecifyingthistypeofequipment,itisnecessarytospecifycarefullyallmedical-gasservicerequirementsandtheirdesiredarrangement(s).Also,theengineermustcoordinateallotherrequiredserviceswiththeelectricalengineerandmedicalstaff.

3. Surgical gas tracks Surgicalgastracksareformsofceilingoutletandhose-droparrangementsthatallowthemovementofthehosedropsfromoneendoftheoperatingtabletotheotheronslidingtracksmountedontheceiling.Theseprod-uctsarecurrentlyavailablefromvariousmanufacturersandallprovidethesamebasicservices.Theproperselectionandspecificationofspecifictypesarebasedonindividualcus-tomerpreference.Manyvariationsinproductsandparticularproductapplicationsareavailableincritical(intensive)careareas.Consultationwithappropriatemanufacturersforrec-ommendationsisalwaysadvisable.

4. Articulating ceiling-service center Articulatedceiling-ser-vicecentersaremovedbypneumaticdrivesystemsandaredesignedfortheconvenientdispensingofmedical-gasandelectricalservicesinoperatingrooms.Themedical-gasandelectricalsystemsarecompleteforsingle-pointconnectiontoeachoutletatthemountingsupportplatform.

High-pressure nitrogen (N2) dispensing equipment Specialconsideration must be given by the plumbing engineer to theplacementofthenitrogenoutlets.Theprimaryuseofnitrogengasinhospitalsisfordrivingturbo-surgicalinstruments.Variationsoftheseturbo-surgicalinstruments,inboththeirmanufactureandtheirintendeduse,willrequirethatseveraldifferentnitrogen-gaspressure levels be available. For this reason, it is necessary thatthe engineer provide an adjustable pressure-regulating devicenear the nitrogen gas outlet. A nitrogen control panel is usuallylocatedonthewall(inthesurgeryroom)oppositetheoperatingareasterilefield.Theinstallationshouldallowfortheaccessandadjustmentofpressuresettingsbyasurgicalnurse.

Pipingfromthenitrogencontrolpaneltoasurgicalceilingoutletwillprovideaconvenientsourceofnitrogenforsurgicaltools.Thiswillpreventhosesfrombeinglocatedonthefloororbetweenthewalloutletandtheoperatingtable.Excesshosecanbeobstructivetothesurgicalteam.

MEDICAl-GASSTorAGEAfterdecidingthemedical-gasservicestobeprovidedatthefacil-ity, the engineer should determine the storage capacity and thepipe sizing required and possible locations for the source. Localcodesandreferencesaswellastheadministrativeauthorityhavingjurisdictionshouldbeconsultedforeachmedical-gassystem.

Because of the unique characteristics of each medical-gassource, the gases are described separately in this section. Also,anexplanationof thetechniquescurrentlyemployedtoexhaustanestheticgasesisprovided.

Oxygen (O2) Severalfactorsmustbeknownwhenestimatingthe monthly consumption of oxygen in new or existing health-carefacilities:1. Typeofmedicalcareprovided.

2. Numberofoxygenoutletsor

3. Numberofpatientbeds.

4. Futureexpansionoffacility.

5. Inexistingfacilities,approximateconsumption.

Two methods can be used by the plumbing engineer to esti-matetheconsumptionofoxygen.Themoreaccuratemethodistoobtainadetailedconsumptionrecordfromthehealth-carefacilityorobtainmonthlyoxygenshipmentinvoicesfromthesupplier.Ifinventoryrecordsarenotavailablefromthehealth-carefacilityorthesupplier,useconsumptionrecords fromacomparablysizedfacility,withgoodjudgment.

Thesecondmethodis toapply the followingruleof thumbtoestimate the monthly supply of oxygen. This estimating methodshouldbeusedwithgoodjudgment.Alwayscoordinateestimateddemandwiththeoxygensupplierduringthedesignprocess.1. Innon-acute-careareas,allow500ft3(14m3)perbedper

monthforsupplyandreserveoxygenstorage.

2. Inacute-careareas,allow1000ft3(28m3)perbedpermonthforsupplyandreserveoxygenstorage.

Oxygensupplysourcesaredividedintotwocategories:(1)bulk-oxygensystemsand(2)cylinder-manifold-supplysystems.Bulk-oxygen systems should be considered for health-care facilitieswithanestimatedmonthlydemandabove35,000ft3(991m3)orequal to 70 oxygen outlets. Manifold systems are used in smallgeneralhospitalsorclinics.

Bulk-oxygen systems Whenselectingandplacingbulk-oxygensystems,thereareseveralfactorstobeconsidered:Oxygentrans-porttrucksize,truckaccesstobulk-storagetanks,andNFPA50,Standard for Bulk Oxygen Systems at Consumer Sites.Bulk-oxygenequipment,construction,installation,andlocationmustcomplywith NFPA 50 recommendations. If liquid oxygen is spilled orleaked,anextremefireorexplosivehazardcouldoccur.NFPAhasdesignstandardstominimizefireexposuretoandfromsurround-ingstructures.

Bulk-storagesystemsconsistofcryogenictanksthatstoreliquidoxygenatlowpressures(225psi[1551.3kPa]orless).CryogenictanksareASMEunfired,double-walled,vacuum-insulated,pres-surevessels.Liquidoxygenhasaboilingpoint(nbp)of–297.3°F(–182.9°C) and a liquid density of 71.27 lb/ft3 (1141.8 kg/cm3).Whenvaporizedintogas,itproduces900timesitsliquidvolume.Furthermore,sincethetankischangedlessoften,processstabil-ityismaximizedandtheintroductionofatmosphericimpuritiesisreduced.Tanksystemsarefurnishedwithanintegralpressure-relief valve vented to the atmosphere should the liquid oxygenconverttoagas.



CONTINUING EDUCATION: Medical Gas and vacuum Systems

Most bulk-oxygen storage systems are furnished with vapor-izers. Vaporizers are banks of finned-tube heat exchangers thatconverttheliquidtoitsgaseousstate.Thevaporizerscomeinsev-eral styles—including atmospheric, powered (forced-air, steam,and electric), waste-heat, and hybrid—and sizes. The selec-tion of vaporizers should be based on demand, intermittent orcontinuous usage, energy costs, and temperature zones. Poorlyventilated sites or undersized heat exchangers can cause ice toformonvaporizersduringtheconversionprocess.Excessive iceformations can clog and damage the vaporizer. Also, ice couldallowextremelycoldgasorthecryogenicliquidtoenterthepipedsystem; damage the valves, alarms, and medical components;andeveninjurepatients.Figure1illustratesatypicalbulk-oxygensystemschematic.

Automaticcontrolsfurnishedwiththetanksregulatetheflowofliquidthroughthevaporizers.Whenthereisademandforoxygen,thesupplysystemdrawsliquidfromthebottomofthecryogenicstoragetankthroughthevaporizers.Thegasmovesthroughafinalline regulator. Thus, a constant supply of oxygen at a regulatedpressureisprovided.

Incaseofmechanicaldifficultyor thedepletionof the liquid-oxygensupply,thereservesupplywillbegintofeedintothedistri-butionsystemautomatically.

An alarm signal should alert appropriate hospital personnelwhen the liquid in the oxygen storage tank reaches a predeter-minedlevel.Thealarmsignalsshouldindicatelowliquidlevels,reserveinuse,andreservelow.

Cylinder-manifold supply systems Compressed-oxygensystems are comprised of cylinder manifolds that allow a pri-marysupplysourceofoxygencylinderstobeinuseandanequalnumberofoxygencylinderstobeconnectedasareservesupply.

Thecontrolsofthecylindermanifoldwillautomaticallyshifttheflow of the oxygen gas from the service side to the reserve sidewhentheservicesideisdepleted.

Manifold systems can be located indoors or outdoors. Whenmanifolds are located indoors, the engineer should observe thefollowing:• Location Preferably,themanifoldshouldbeinadedicated

roomonanoutsidewallnearaloadingdockandhaveade-quateventilationandserviceconvenience.

• Adjacent areas Thereshouldbenodoors,vents,orotherdirectcommunicationsbetweentheanesthetizinglocationorthestoragelocationandanycombustibleagents.Iflocatingnearoradjacenttoanelevatedtemperatureareaisunavoid-able,theengineershouldspecifysufficientinsulationtopre-ventcylinderoverheating;

• Fire rating Thefire-resistanceratingoftheroomshouldbeatleast1h.

• Ventilation Outsideventilationisrequired.

• Security Theroom(orarea)mustbeprovidedwithadoororagatethatcanbelockedandlabeled.

Oxygen manifolds are sized taking into consideration the fol-lowing:1. Thesizeofthecylinders,244ft3(6909L)H-cylinder(seeTable

4forasizingchart).

2. Thehospital’susageofoxygen,inft3(L)permonth.

Figure 1 Typical Bulk Supply System (Schematic)



table 4 Selection Chart for Oxygen ManifoldsHospital Usage Duplex Manifold Size

Cu. Ft. (103 L) per month Total Cylinders Cylinders per Side5,856 (165.8) 6 39,760 (276.4) 10 5

13,664 (386.9) 14 717,568 (497.5) 18 921,472 (608.0) 22 1125,376 (718.6) 26 1329,280 (829.1) 30 1533,154 (938.8) 34 17

Note: Based on use of 244 ft3 (6909.35 L) H-cylinders.

Nitrous oxide(N2O) Thecommonsourceofnitrousoxideisacylinder-manifold system. High-pressure manifold systems con-sistof twobanksofcylinders,primaryandreserve. (Seediscus-sionunder“Oxygen,”above.)

Systemdemandsfornitrousoxidecanbemoredifficulttodeter-minethantheyareforothermedicalgases.Thenumberofsurger-iesscheduled, the typesand lengthsofsurgery,andtheadmin-istering techniques used by the anesthesiologists cause extremevariations in the amount of nitrous oxide used. Because of thisvariation,considerationsmustbegiventothesizeandselectionofthenitrous-oxidemanifoldsystem.

Avoid locating the nitrous-oxide manifold system outdoors inareaswithextremelycoldclimates.Nitrousoxideissuppliedlique-fied at its vapor pressure of 745 psi (5136.6 kPa) at 70°F (21.1°C).At extremely cold temperatures, the cylinder pressure will dropdramatically,reducingthecylinderpressuretoapointwhereitisimpossibletomaintainanadequatelinepressure.Thisisduetoalackofheatforvaporization.

Fornitrous-oxidemanifoldslocatedindoors,thesameprecau-tionspreviouslylistedforoxygensystemsmustbeobserved.

Thefollowingshouldbeconsideredwhenselectingandsizingnitrous-oxidemanifoldsanddeterminingthenumberofcylindersrequired:1. Thesizeofthecylinders:489ft3(13847L)K-cylinders(see

Table5).

2. Thenumberofanesthetizinglocationsoroperatingrooms.

3. Provide½of1cylinderperoperatingroomforin-serviceandreservesupplies.

table 5 Sizing Chart for Nitrous Oxide Cylinder Manifolds

Number of Operating

Rooms

Duplex Manifold SizeIndoor Outdoor

Total CylindersCylinders per

Side Total CylindersCylinders per

Side4 4 2 4 28 8 4 10 5

10 10 5 12 512 12 6 14 716 16 8 20 10

Note: Based on use of 489 ft3 (13.85 × 103 L) K-cylinders.

Medical compressed air Medical compressed air may besupplied by two types of system: (1) a high-pressure cylinder-manifoldsystem;and(2)amedicalair-compressorsystem.

Themanifoldsystemsforcompressedairaresimilarinconfigu-rationtothoseforoxygenandnitrousoxide(seediscussionunder“Oxygen,” above). Air supplied from cylinders or that has been

reconstitutedfromoxygenU.S.P.andnitrogenN.F.mustcomply,asaminimum,withGradeDinANSIZE86.I,Commodity Specifi-cation for Air.

Medical compressed air can be produced on site from atmo-spheric air using air compressors designed for medical applica-tions.Therearethreemajortypesofaircompressorinthemarket-place today: the centrifugal, reciprocating, and rotary screw. Thereciprocating and rotary screw are “positive-displacement” typeunits,whilethecentrifugalcompressor isa“dynamic”typecom-pressor.Themedicalaircompressorshallbedesignedtopreventtheintroductionofcontaminantsorliquidintothepipelinebyoneoftwomethods:Type1aircompressorseliminateoilanywhereinthecompressor.Type2aircompressorsseparatetheoil-containingsectionfromthecompressionchamber.Examplesofatype1com-pressorare the liquidring, rotaryscrew,andpermanentlysealedbearingcompressor.Type2compressorshaveextendedheads.

Apositive-displacementcompressorisnormallyratedinactualcubicfeetperminute(acfm).Thisistheamountofairtakenfromatmosphericconditionsthattheunitwilldeliveratitsdischarge.Withinabroadrange,changesininletairtemperature,pressure,andhumiditydonotchangetheacfmratingofeithertherecipro-catingor therotaryscrewcompressor.Thecentrifugalcompres-sor’scapacity,however,isaffectedslightlybytheinletaircondi-tionsduetothenatureofthecompressionprocess.Forexample,as the air temperature decreases, the capacity of the dynamiccompressorwillincrease.Thecapacityofacentrifugalcompres-sorisnormallydefinedininletcubicfeetperminute(icfm).Inanefforttoobtainan“applestoapples”comparisonofvariouscom-pressors,manymanufacturersspecifytheircapacityrequirementsinstandardcubicfeetperminute(scfm).Thissometimescausesmuch confusion because many people do not fully understandhow to convert from acfm or icfm to scfm. The design engineerspecifying scfm must define a typical inlet air condition at thebuildingsiteandtheirsetof“standard”conditions(normally14.7psia [101.4 kPa], 60°F [15.6°C], and 0% relative humidity). Typi-cally, the warmest normal condition is specified because as thetemperaturegoesupscfmwillgodown.

Toconvertfromacfmtoscfm,thefollowingequationisused.

Equation 1

scfm =acfm×Pi–(Ppi×%RH)

× Tstd

Pstd–(Ppstd×%RHstd) Ti

where Pi=Initialpressure Ppi=Partialinitialpressureofwatervaporin100%humidairat

thetemperatureinquestion RH=Relativehumidity Pstd=Pressureunderstandardconditions Ppstd=Partialstandardpressureofwatervaporin100%humid

airatthetemperatureinquestionRHstd=Relativehumidityatstandardconditions Tstd=Temperatureatstandardconditions,°F(°C) Ti=Inlettemperature,°F(°C)



CONTINUING EDUCATION: Medical Gas and vacuum SystemsEquation 1a

ThisequationisderivedfromthePerfectGaslaw,whichis:P1V1 =

P2V2

T1 T2

or:

V2=V1× P1 × T2P2 T1

where P1=Initialpressure V1=Initialvolume T1=Initialtemperature P2=Finalpressure V2=Finalvolume T2=Finaltemperature

Forareciprocatingorrotary-screwcompressor,theconversionfromacfmtoscfmissimple.Theinletairconditionsandstandardconditions are inserted into the above formula and multipliedbytheacfmcapacityoftheunit.Itmakesnodifferencewhatthedesignconditionsareforthatcompressor,asthesedonotfigureintotheformula.Inthecaseofadynamiccompressor,theicfmairflowatthegiveninletconditionsisinsertedinplaceoftheacfmintheformula.Anotherdesignissuethattheengineershouldbeawareof ishowaltitudeaffectstheoutputofthecompressor.Ataltitudes above sea level, all medical-air systems have reducedflow.Inthesecases,therequiredsizingwillneedtobeadjustedtocompensate.Todothis,multiplythescfmrequirementsbythecorrectionfactorinTable6.

table 6 Altitude Correction Factors for Medical-Air Systems

Altitude, ft (m)Normal Barometric

Pressure, in. Hg (mm Hg)

Correction Factor for SCFM

(L/min) Sea level 29.92 (759.97) 1.0 (28.31)

1,000 (304.8) 28.86 (733.04) 1.01 (28.6) 2,000 (609.6) 27.82 (706.63) 1.03 (29.16) 3,000 (914.4) 26.82 (681.23) 1.05 (29.73) 4,000 (1219.2) 25.84 (656.33) 1.06 (30.01)

5,000 (1524) 24.90 (632.46) 1.08 (30.58) 6,000 (1828.8) 23.98 (609.09) 1.10 (31.14) 7,000 (2133.6) 23.09 (586.48) 1.12 (31.71) 8,000 (2438.4) 22.23 (564.64) 1.15 (32.56) 9,000 (2743.2) 21.39 (543.3) 1.17 (33.13)

10,000 (3048) 20.58 (522.7) 1.19 (33.69)

In other words, to correctly size the medical-air system, youwouldapplythecorrectionfactorlistedinthechartabovetothepeak-calculatedload(scfm)atsealevel.

Example 2 Afacilityislocatedat5000ft(1524m)abovesealevelandthesystemdemandis29.4SCFM.Takethe29.4scfmandmultiply itby1.08(correctionfactor fromTable5) toget theadjustedscfmrequire-mentof31.8scfmat5000ftabovesealevel.Therefore,amedical-airsystemofgreatercapacityisneededathigheraltitudes.

Another handy formula for compressed-air systems is the fol-lowing:toconvertscfmtoL/minmultiplyby28.31685.

Each compressor must be capable of maintaining 100% of themedical-airpeakdemandregardlessofthestandbycompressor’soperating status. The basic compressor package consists of filterintakes, duplex compressors, after-coolers, receiving tanks, air

dryers, in-line filters, regulators, dew-point monitors, and valves.Thecompressorcomponentsareconnectedbypipingthatallowsequipment isolation, provides pressure relief, and removes con-densate from receivers. Medical-air compressors must draw out-sideairfromabovetherooflevel,remotefromanydoors,windows,andexhaustorventopenings.Wheretheoutsideatmosphericairispolluted,specialfilterscanbeattachedtothecompressor’sintaketo remove carbon monoxide and other contaminants. Refer toNFPA99forproperlocationofmedical-airintakes.Medicalcom-pressedairmustcomplywithNFPA99and/orCanadianStandardsAssociation’s(CSA’s)definitionofair-qualitystandards.

Wheremorethantwounitsareprovidedforthefacility,anytwounitsmustbecapableofsupplyingthepeakcalculateddemands.Provide automatic alternators (duty-cycling controls) to ensureevenwearinnormalusage.Alternatorcontrolsincorporateaposi-tivemeansofautomaticallyactivatingtheadditionalunit(orunits)shouldthein-servicepumpfailtomaintaintheminimumrequiredpressure.

Medical compressed air produced by compressors may bedefinedas“outsideatmospheretowhichnocontaminants(intheformofparticulatematter,odors,oilvapors,orothergases)havebeenaddedbythecompressorsystem.”Noteverycompressorissuitableforuseasasourceformedicalcompressedairinhealth-carefacilities.Onlythosecompressorunitsspecificallydesignedandmanufacturedformedicalpurposesshouldbeconsideredasa reliable source of oil-free, moisture-free, and low-temperaturecompressedair.Acceptablecompressortypesincludeoil-free,oil-less,andliquid-ringcompressors.Separationof theoil-contain-ingsectionfromthecompressionchamberbyatleasttwosealsisrequiredbythecompressormanufacturers.

Aircompressedformedical-breathingpurposesaretobeusedfor this purpose only and should not be used for other applica-tionsorcross-connectedwithothercompressedairsystems.

table 7 Minimum Pipe Sizes for Medical Air-Compressor Intake Risers

Pipe size, in. (mm)

Flow rate, cfm (L/min)

2.5 (63.5) 50 (1416)

3 (76.2) 70 (1985)

4 (101.6) 210 (5950)

5 (127.0) 400 (11330)

Table7providestheminimumpipesizesformedicalair-com-pressorintakerisers.Consultwiththecompressormanufactureron intake recommendations and allowable friction loss for theintakeriserbeforefinalizingthepipesizeequipmentselection.

0 PlumbingSystems&Design JANUARY/FEBRUARY 2006 PSDMAGAZINE.ORG



1. when liquid oxygen is vaporized into a gas, it produces ________ times its liquid volume.a. 0b. 450c. 900d. 1,350

. Nitrous oxide (NO) is typically used by whom in the surgery room?a. the attending physicianb. the attending physician’s assistantc. the surgical nursed. the anesthesiologist

. The medical-gas and vacuum piping systems must be designed to ________.a. meet the specific requirements of each hospitalb. anticipate any building expansionc. not cross connect to any existing systemd. all of the above

. The primary use of nitrogen gas in hospitals is ________.a. driving turbo-surgical instruments b. pressurizing piping systemsc. in the laboratory Bunsen burnersd. none of the above

. Medical-gas flow rates ________.a. must include diversificationb. must provide for the total connected loadc. must provide the minimum required flow for the

proper functioning of connected equipmentd. must be estimated

. Providing medical-gas service outlets in the surgery room may be accomplished by locating them in ______.a. the ceilingb. the surgical ceiling columnsc. the surgical gas tracksd. any of the above noted areas and others not listed

. In acute-care areas, allow ________ cubic feet per bed per month for supply and reserve oxygen storage.a. 250b. 500c. 750d. 1,000

. The exact number of medical-gas outlets required in the various areas or rooms is mandated by ________.a. the various codes that apply to work at the project

siteb. the American Institute of Architects (AIA)c. the National Fire Protection Association (NFPA)d. none of the above

. Medical-gas outlet types and configurations must meet the requirements of the local jurisdictional authority and ________.a. ANSI 1416 b. NFPA 99c. NFPA 50d. ANSI 1763

10. Several factors must be known when estimating the monthly consumption of oxygen, such as ________.a. the number of patient bedsb. the type of medical care providedc. the future expansion plans of the facilityd. all of the above

11. what is the SCfM correction factor for a medical-air system located in a facility at an altitude of ,000 feet above sea level?a. 1.05b. 1.08c. 1.12d. 1.17

1. The goal in designing medical-gas and vacuum systems is ________.a. to provide a safe systemb. to provide a sufficient flow of gas or vacuumc. to provide the required pressured. all of the above

Doyoufinditdifficulttoobtaincontinuingeducationunits(CEUs)?Is it hard for you to attend technical seminars? Through PlumbingSystems&Design(PS&D),ASPEcanhelpyouaccumulatetheCEUsrequired for maintaining your Certified in Plumbing Design (CPD)status.

ASPEfeaturesatechnicalarticleineveryissueofPS&D,excerptedfromitsownpublications.Eacharticleisfollowedbyamultiple-choicetestandasimplereportingform.

Readingthearticleandcompletingtheformwillallowyoutoapplyto ASPE for CEU credit. For most people, this process will requireapproximately 1 hour. A nominal processing fee is charged—$25 forASPE members and $35 for nonmembers (until further notice, thememberfeeiswaived).Ifyouearnagradeof90%orhigheronthetest,

youwillbenotifiedthatyouhavelogged0.1CEU,whichcanbeappliedtowardtheCPDrenewalrequirementornumerousregulatory-agencyCEprograms.(Pleasenotethat it isyourresponsibility todeterminetheacceptancepolicyofaparticularagency.)CEUinformationwillbekeptonfileattheASPEofficefor3years.

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Note:IndeterminingyouranswerstotheCEquestions,useonlythematerial presented in the continuing education article. Using otherinformationmayresultinawronganswer.

Continuing Education from Plumbing Systems & DesignKenneth G.Wentink, PE, CPD

CE Questions—“Medical Gas and Vacuum Systems” (PSD 131)



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PSD

133

Reflecting Pools and Fountains


MAY/JUNE 2006

PSDMAGAZINE.ORG


InTRODuCTIOnReflectingpoolsandfountainsprovidevisualandauditoryplea-sure, add charm to garden areas, and provide a retreat area inwhichtorestandrelax.Fountainsgeneratesoundandprovidea cooling effect on hot summer days. Fountains may be self-contained units or pre-engineered kits or they may be customdesignedandbuilt.Self-containedfountains,consistingofpools,pumps, valves, lights, and other hardware, are shipped assem-bled,andtheadditionofwaterisallthatisnecessarytoputthefountain into normal operation. No permanent connections totheplumbingsystemarerequired.Pre-engineeredfountainkits,completewithequipment,needonlyassemblyandhook-uptothewater-supply,drainage,andpowersources.

Plumbingengineers,architects,andlandscapearchitectsareall involved in the creation of display fountains and reflectingpools. The architects are concerned with the overall aesthet-ics,whereas theengineersmustbe familiarwith theavailablefountain equipment and the technical details of each compo-nentiftheyaretodesignsystemsthatwillachievethedesireddisplayeffects.Theplumbingengineershouldworkcloselywiththearchitectandthelandscapearchitecttoachievethedesireddisplay.Inaddition,thesystemsshouldbedesignedwithprovi-sionsforcleaning,watertreatment,andmaintenance.Customfountains providing small or large water displays with almostanydesireddecorativeeffectsarediscussedinthischapter.Alsoincluded are the technical details of pool design; mechanicalequipment,includingspraysystems;andoperationandmain-tenance.

Theengineermustalsobeawarethatthefountainisusuallyrep-resentedonasetofarchitecturaldrawingsasanundefinedspaceor a rendering. It is also usually the last item to be coordinated.Whatthismeansisthattheengineerusuallydesignsthefountaininitsentirety,includingthewatereffectanditsinfluenceonthesurroundingarea.Then,he/sheneedstoquickly(andaccurately)selectthenozzles,determineflowrates,selecttheequipment,tryto get space for the equipment, coordinate with the other disci-plinesinvolved,thencoachcontractors,wholookuponafountainasaglorifiedswimmingpool.Whenallthisisdone,however,theengineercanlookuponabeautifulpieceofengineeredartthatwillmostlikelyneverbeduplicatedandcanbeproudtoclaimitashis/herwork.

POOLDESIGn

GEnERALCOnSIDERATIOnSA number of general items of information should be kept inmindwhendesigningafountain.

For an engineer or designer, the most important issue sur-rounding any body of water is safety. There is always a riskattached to a water feature. It is not the intent of this chaptertoacquainttheengineerwithdrowningandentrapmentissues,but the engineer is encouraged to study the available codes

and standards regarding swimming pools and spas and applythemasnecessary.Manyjurisdictionsregard18in.(457.2mm)ofwaterasthemaximumdepthallowedwithoutsevereaccessrestrictions,suchasrailings,fences,andgates.

From a mechanical, operating perspective, the most impor-tantthingistolocateallpumpstoensurefloodedsuctionlines.Ifatallpossible, locatethepumpssothattheoperatingwaterlevelofthefountainisabovethesuctioninletofthepump.Thishelpstopreventcavitationandtoensurethatthepumpprimesquickly.

Paintingthepoolinterioradarkcolorhelpstoconcealpiping,lighting,cable,junctionboxes,andotherequipmentlocatedinthepool,and,inaddition,providesreflectivequalities.Butthedarkcolortendstocauseanincreaseinwatertemperaturebyabsorbingthesun’sheat.This,inturn,createsarequirementformorechlorine.Thinorfine-mistsprayeffectsaredifficulttoseeagainstlightcolors,mixedcolors,orlace-typebackgrounds.Amassivedisplayshouldbeusedundertheseconditions.

The construction of pools at or below grade level creates apotential problem with leaves and other debris blowing intothepool,therefore,thisshouldbeavoided.Reflectingpoolsandfountains may be installed above or below grade. Above-gradefountainsoffertheadvantageofaddingmoreheighttothewaterdisplay.Multilevelpoolsprovidethepossibilityofhavingnumer-ouswaterfalldisplayswithonlyonewatersource.

Aeratingnozzlesthatuseaventuriactiontoentrainairintothewaterstreamcancauseawaveactionincircularpools.Insuchcases,surgecollarsorunderwaterbafflesshouldbeinstalledtominimizethisaction.

Water will splash horizontally approximately one half theheight of the water display except where wind is a problem.Since wind can push water long distances, it is important tolocatenozzlessothatthesplashandwindeffectwillnotcreateundueproblems.Itmaybeadvisabletoprovideawindcontroltolowertheheightofthedisplayortoshutoffthesystemwhenthereistoomuchwind.

Waterhittingwatercreatesalotofnoise.Therearetimesandlocations when this is desirable. When the noise is too loud,however,itcanbereducedbylocatingvarioustypesofplantingaroundapool.

MuLTILEVELPOOLSMultilevel and multiple pools involve special considerations,which, if taken into account, do not present any difficulty. Iftheseconsiderationsarenottakenintoaccount,however,disas-tercanresult.

The amount of flow over a waterfall is determined by theheight of the water flowing over the weir. This height over theweiristhesameastheheightofthepoolbehindtheweir.Whenthepumpsstop,thiswaterwillallcomeovertheweirandspillintothepoolbelow.Thewaterintheair(i.e.,thewaterfall)willalsocometorestinthelowerpool.Thelowerpoolmustbesized

COnTInuInG EDuCaTIOn

Reflecting Pools and Fountains

Reprinted from American Society of Plumbing Engineers Data Book Volume 3: Special Plumbing Systems, Chapter 5: “Reflecting Pools and Fountains.” © 2000, American Society of Plumbing Engineers.

PlumbingSystems&Design MAY/JUNE 2006 PSDMAGAZINE.ORG


to accommodate this extra water. For the water in the air, thedepthovertheweirtimestheheightofthewaterissufficientlyaccuratetocalculatethevolume.

Multilevel pools should have some method of draining theupperpools.Asmalldrainlinewithascrewplugattheupperpoolcanbeused.Thedrainlineshouldbeamaximumof1¼in.(31.75mm)torestrictthedischargerateintothelowestpool.

Formultiplepoolswithdifferentelevations,acommonrefer-encemustbeestablishedtodrainthebasins.Anexamplewouldbewaterfallsatseveraldifferentelevationswithbasinsatsev-eraldifferentelevationsservedbyasinglepumpsystem.Ifthepumpswereturnedoff,thewaterinthebasinswouldalldraintothelowestbasinthroughthecommonsuctionheader.Topre-ventthis,eithercheckvalvesmustbeinstalledinallsuctionanddischargelinesorallbasinsmustdraintoasurgepit.Thesurgepit provides a common reference for the pumps and allowseachbasintodrainindependentlyoftheothers.Thesurgepitmethod is also much easier to balance than the method withcheckvalves.(SeeFigure1.)

For multiple pools at the same elevation, an equalizer lineshouldberunbetweenthepools.Nomatterhowaccuratethecalculationsandinstallation,twoidenticalpoolswillhavevary-ingflowrates.Theequalizer lineshouldnottie intoanyotherlineexceptavalveddrain.Theequalizershouldbesizedsothatitisaslargeasthelargestlinecomingintothepools.Ifeachpoolreceivesthedischargethrougha4-in.(100-mm)line,theequal-izershouldbea4-in.(100-mm)line.

PRELIMInARyDISPLAySELECTIOnAnDDETERMInATIOnOFFLOWRATESSpray jets and nozzlesTheflowratesforsprayjetsandnozzlesshouldbedeterminedbythemanufacturer’sdata.Mostmanu-facturers publish catalogs showing the various types of jet inoperation.Theclientshouldbegiventheopportunitytoselectthejetsfromasubjectivestandpoint;theselectionshouldthenbereviewedbytheengineerforpracticality.Weirs Weirsarenormallysizedbythelengthoftheweirandthedepthofthewaterflowingovertheweiredge.Theengineermayhavetoassisttheclientindeterminingtheeffectdesired.Itisusefultohavetheclientseeanexistingwaterfeaturethen

actuallymeasurethedepthoveraweir.Iftheclientdesiresanunbroken sheet of water over the weir into the pool, a rule ofthumbisabout¼in.(6.35mm)ofwaterovertheweirper4ftofverticaldrop.

Thefourmostcommontypesofweiraretheroundededge;theupward-taperedweir;thedownward-taperedweir;andthedownward-tapered, metal-edge weir. The rounded-edge weirisusedwhenitisdesiredtohavethewaterrundownthewallsurface.Theupward-taperedweirrequiresmorewaterthantheothertypesandshouldnotbeusedforwaterfallsexceeding5ftinheight.Thedownward-taperedweirisveryeffectiveincreatingsmoothsheetsforwaterfallsupto15ftinheight.Thedownward-tapered,metal-edgeweirachievesthesameeffectasthedown-ward-taperedweirwiththeaddedadvantageofbeingeasiertolevel.

The waterfall or weir is normally supplied from a troughbehind the weir edge. The trough can be supplied with waterbymanymethodsaslongasthesurfacedisturbanceiskepttoaminimum.Aheadercanbeinstalledwithholesdrilledalong

the length of the header to supplywater equally along the length ofthetrough.Hydrophilicwellpiping,precut with slots along the lengthof the pipe, makes a very smoothsupply method. Oversized inlets(to lower the water velocity) in thebottom of the trough with diverterplatescanalsobeused.

Weirlipsmustbelevel.Thisisdif-ficult to achieve with poured con-crete,therefore,ametalorplasticlipshouldbeprovided.Ifthespilllipisin theshapeofanoverhang,adriplipintheshapeofa¼in.(6.35mm)deeprectangularslotshouldbepro-vided under the slot. This will pre-vent the water from running downthewall.Filtration turnover The filtrationturnover rate is determined by the

volumeofthepoolandthedesirednumberofhourspercom-plete water change. The filtration turnover can vary from 4 to12hpercompletewaterchange.Thisneedstobedeterminedby the engineer. For areas with blowing dust and debris, afasterwaterchangeisneeded.Forcleanerareas,suchasthoseindoors,aslowerwaterchangecanbeused.Thefiltrationflowrateisdeterminedbydividingthepoolwatervolume,ingallons(liters),bytheturnovertime,inminutes.Example 1An8000-galpooldividedby(12hx60min)equals11.1gpmflowrate.(A30283-Lpooldividedby[12hx60min]equals45.42L/minflowrate.)Therefore,afiltrationsystemsizedforaflowrateof12gpm(45.42L/min)wouldbeadequate.

InLET/OuTLETAnDDEVICELOCATIOnByconvention,an“inlet”isdefinedasadeviceallowingwatertoflowintothepool.An“outlet”isdefinedasadeviceallowingwatertoleavethepool.

Figure 1 Multilevel Pools with a Surge Pit

MAY/JUNE 2006 PlumbingSystems&Design


COnTInuInG EDuCaTIOn: reflecting Pools and fountains

Main drains Maindrainsareprovidedforpumpsuctionanddrainingthepool.Maindrainsshouldbelocatedatthelowestpointof thepool.Thereshouldbeat leastonemaindrain forthelowestbasin.Maindrainsshouldbelocatedsothatthereisnotmorethan20ftbetweendrainsormorethan15ftfromthesidewallofthepool.Themaindrainsshouldbesizedtoaccom-modatethefullflowofthesystem.Main-draingratingsshouldbesizedatnogreaterthan1.5fpsthroughthegrating.Seethemanufacturer’slistingsfortheapprovedflowratethroughanti-vortexgratings.

Maindrainsusedforpumpsuctionmusthavesomemethodof preventing entrapment: either they must be the anti-vortextype or they must beinstalled in pairs atleast 4 ft apart to pre-vent suction entrap-ment.Althoughreflect-ingpoolsandfountainsare not intended to beoccupied by humans,people do acciden-tally (and on purpose)fall into them. Pair-ing drains and usinganti-vortex drainsminimizes the risk ofsuctionentrapmentanddisembowelment.Ifpaireddrainsareused,theymustbeconnectedtoacommonsuctionlinewithoutanyinterveningvalves.(SeeFigure2.)

Main drains are used to empty the pool for cleaning and todrainstormwaterwhenthepoolisempty.Adrainlineisruntotheneareststormdrainlineandavalveisinstalledinthisline.Skimmers Skimmers are necessary in all pools to collectwindblown debris and dust. Even indoor pools can collect anamazing amount of floating debris that must be cleaned outperiodically.Skimmersnormallyconsistofaskimmerbodythatiscastintothepoolwall,afloatingweir,andastrainerbasket.Thefloatingweirdrawsathinlayerofwaterintotheskimmer.Withathinlayer,thewater’svelocityishigheranditsinfluenceextendsfartheroutintothepool.Skimmerstrainerbasketsneedtobecleanedoutperiodically,andaccesstothestrainerdefinesthetypeofskimmerused.Top-accessskimmers,whileeasiesttomaintain,areveryvisible.Sincearchitectsprefertohideeverycomponentpossible, front-loadingskimmersarepreferred. Inaddition,front-loadingskimmersarelesspronetovandalism.

Skimmersshouldbelocatedsothatthereis1skimmerpro-videdforeach500ft2(46.45m2)oflowerbasin,withaminimumof1skimmer.Theskimmersystemshouldbesizedtoaccom-modatethefullfiltrationflow.A2-in.(50.8-mm)skimmercanaccept about 30 gpm (113.56 L/min), but skimmers can beganged together to increase their capacity. A majority of theskimmersshouldbelocatedsuchthattheprevailingwindsandcurrentblowthedebristowardthem.Filtration return inlets Filtrationreturninletscomefromthefiltersandreturncleanwatertothepool.Returninletsshouldbeplacedatleast12in.(304.8mm)belowwaterleveltominimizesurfacedisturbance.Ifthepoolistooshallow,increasetheinletpipesizetoreducethevelocityintothepool.Eachpoolshouldhaveaminimumof2inlets,withasizingcriteriaof1inletper600ft2(0.093m2)ofbasin.Inletsshouldbesitedtodirectflowtowardtheskimmers.

Mechanical space or vault Thepumpingequipmentcanbelocatedinthebuilding,inanundergroundequipmentvault,oroutdoorsabovegroundinaprotectedarea.Thedeterminationastowhetherornottoprovideavaultdependsonthefollowingfactors:(1)thedistancefromthepooltothemechanicalspaceinthebuildingvs.thedistancefromthepooltoanundergroundvault;(2)thedifferenceincostforpiping,electricalwiring,andconduitbetweenthetwolocations;(3)thecostofthemechani-calspacevs.thecostofavault;and(4)whetherornotmechani-calspaceisavailable.

Iftheequipmentisinstalledinanarearemotefromthefoun-tain,itisadvisabletohavearemote-controlpanellocatedwithinviewofthefountain.

Provideadequatespaceforallfountainequipment,includingelectricalpanels.Observeallcode-mandatedclearancerequire-ments.Allowsomemethodofremovingmotorsandpumpsthatwillnotrequiretheremovalofpartsofthebuilding.Thiscouldbeanoverheadcranerailormerelyaneyeboltattachedtothestructureovereachmotorforlifting.

Afloordrainisrequiredneartheequipment.Specifyafloordrainwithabackwatervalveifthereisanypossibilityofwaterbacking up through the drain, especially in a vault. If a floordraincannotflowbygravitytothesewer,asumppitandpumpis required. If the equipment is installed in a vault, a battery-operated,backupsumppumpmaybedesirable.

Inavault,provideanelectricreceptacle;alight;ahosebibb;aventilatingblower;intakeandexhaustvents;anaccessladder;and a lockable, spring-loaded access hatch big enough for allequipment to pass through. A heavy manhole cover is notrecommended because the maintenance personnel becomeannoyedwithliftingthecoverandtendtoforgettheirmainte-nance duties. In some cases, a 3-ft deep vault with an accesshatchcoveringtheentirevaultisadequate.

FOunTAInSySTEMSAnDCOMPOnEnTSThefountainsystemconsistsofthefollowingmajorsystems:1. Displaysystem.

2. Pipingsystem.

3. Water-treatmentsystem.

A. Mechanical-filtrationsystem.B. Chemical-treatmentsystem.

4. Makeup-watersystem.

5. Overflowanddrainagesystem.

6. Lightingsystem.

7. Othermiscellaneoussystems.

The reflecting pool may or may not have a display system,dependingonthedesiredeffect.

Each of these systems often overlaps or relies on anothersystemtofunctioncorrectly.Forinstance,ifthefiltrationsystemisnotworkingproperly,thesprayheadswillloadupwithdebrisandnotfunctioncorrectly.Ifthewaterisnotkeptattheproperlevelwithanautofill,thelightingsystemmayoverheat.

DISPLAySySTEMTherearetwodistinctdisplaytypes:staticanddynamic.Staticdisplayshaveaconstantornearlyconstantvolumetricflowrateat all times. Examples include a waterfall weir and constant-heightjets.Dynamicdisplaysvarytheflowthroughthesystem.Examplesaredancingfountains,wherethefountainappearstoreacttomusicor lights,andwaterfallsandriversthatarepart

Figure 2 Main Drains



of a simulated storm scenario. For either type of display, thetypical system consists of the following components: suctionoutlets and suction piping, pump(s), return piping, and dis-chargedevice(s).Thedisplaysystemforeachtypeofeffect,e.g.,nozzles, weirs, whirlpools, and waves, should have a differentpumpsystemdedicatedtoit.

PIPInGSySTEMTwoseparatetypesofpipingsystemsaredefinedforanyfoun-tain. These are the display systems and the filter system. Thepipingforthesesystemscannormallysharesuctionoutletsbutshouldremainseparatefromthereuntilreturningtothepool.Anexampleofapoordesignisafountainsystemwherethedisplaywaterandthefilterwaterarecombinedsuchthatasinglepumpdrawsfromthepoolandpumpsthroughthefilterthenbacktothenozzle.Whenthefilterisclean,thissystemwillworkfine.Assoonasthefiltergetsdirty,however,theflowfromthenozzlewillgraduallydropuntilthefilterisbackwashed.Thenthecyclewillbeginagain.

WATER-TREATMEnTSySTEMThewater-treatmentsystemconsistsoftwoseparateprocesses.First,mechanicalfiltrationremovesthesolidsandsomeofthesuspendedorganicsfromthewater.Second,thechemicalfiltra-tion disinfects and balances the water to provide clean, spar-kling clear, odor-free water that is pleasing to the eye and notdetrimentaltothepoolandequipment.

MAKEuP-WATERSySTEMItisessentialtomaintaintheproperwaterlevelinthepool.Thereasonsarethreefold.First,certainspraynozzlesrequirethatthewaterlevelvarynomorethan½in.(12.7mm)inordertoachievethedesireddisplay.Avariationinthewaterlevelcausesthenozzledisplaytobecomeerraticandtodifferfromtheoriginaldesign.Second,underwaterlightsmustbesubmergedtoaspecificdepthtobothprotectthelightsandtoremoveheat.Third,asubstantialwater-leveldropcouldcausethesuctionlinetoentrainair,resultinginpumpcavitationandpossibledamage.

OVERFLOWAnDDRAInAGESySTEMThe fountain must be equipped with an overflow systemto handle storm water and the possible malfunction of themakeup-watersystem.Inaddition,mundanereasons,suchasdrainingthepoolforwinterandcleaning,mandatethatadrainsystembeinstalled.

WATER-HEATInGSySTEMIfafountainistobekeptinoperationduringthewintermonthsanditispossibleforthewatertofreeze,anaquastat-controlledpoolheatershouldbeprovided.Theheatershouldbesizedtomaintainpoolwateratabout35to40°F(1.67to4.44°C).

LIGHTInGSySTEMUnderwaterlightsareusedtoprovideilluminationforthevari-ousdisplays.Thenumberoflightsdependsontheoverallsizeofthepool,thedepthofthewater,theheightandwidthofthewaterdisplay,andpossibleinterferencefromambientlighting.Lightscanbewhiteoranothercolorasdesired.

SySTEMAnDCOMPOnEnTSELECTIOnAnDDESIGnCRITERIA

FILTERSySTEMSTypes of filter There are many types of filter on the markettoday. Some of these are specialty filters for water treatment,ROsystemsandthelike.Forfountains,swimmingpoolandspafiltersbestfittheapplication.Mechanicalfiltrationisrequiredtoremovesuspendedparticulatesdowntoabout50µ. In thisrange, cartridge filters and high-rate, pressure sand filters arethebestchoiceforfountains.

There is a division in filter sizes that occurs around the 120gpm(454.25L/min)flowrate.Abovethatratearethecommer-cialfiltersusedonlargerpoolsandfountainsandbelowaretheresidential filters used on smaller pools and fountains. Manymanufacturers do not make a distinction regarding quality atthe different levels, but some do. Check with the distributorsandpoolcontractorsastowhichfilterscausetheleasttrouble.

Whensizingfilters,itisgoodpracticetousemorethanonefilterwhentheflowrateisabove120gpm(454.25L/min).Forexam-ple,asystemthatrequires280gpm(1059.92L/min)offiltrationwoulddobetterwithtwofilterssizedat140gpm(529.96L/min)eachthanonefiltersizedat280gpm(1059.92L/min).Thereasoniscleaningtime.Whetherthefilterselectedisacartridge,sand,ordiatomaceousearth(DE), itwillhavetobecleanedatsometime.Withmultiplefilters,thefiltrationprocesscontinueswhileonefilterisbeingcleaned.Inthecaseofsandfilters,thefiltertypeofchoiceformostlargesystems,thebackwashflowrateislower,necessitatingasmallerbackwashpitandsewerline.

Withmultiplefilters,usemultiplepumps.Althoughthepumpsare not to be piped individually to each filter, a pump can beshutdownwhileafilterisserviced.Thiswillpreventoverrun-ningtheotherfilterswhileonefilterisdown.

Cartridge filters Cartridgefiltersarelowerinfirstcostthantheothertypesoffiltersandarerelativelyeasytomaintain.Thefilterconsistsofabodyconstructedofplasticorstainlesssteelthatcontainsapolyesterelement.Thecartridgefilterelementiscleanedbyremovingthefiltertopandpullingouttheelement.Itcanthenbehosedcleanandreinstalledinthebody.Thesefil-tersareavailableinsizesrangingfrom150gpmdownto5gpm.Thesmall-sizefiltersareoftheinlinetypemadeforfilteringspasandareexcellentforsmallfountains.

Cartridgefiltersmustberemovedfromthebodytobecleanedandrequiresomespacetobehoseddown.Thisisaconsider-ation when the fountain is indoors and requires that the car-tridgesbetakenawaytobecleaned.Asecondsetofcartridgeswillbenecessaryforaswap.

Cartridges should be sized at 0.375 gpm/ft2 maximum flowrate.

High-rate, pressure sand filters Apressuresandfiltercon-sistsofabodyconstructedofplastic,fiberglass,orstainlesssteelthatcontainssandtofilterthewater.Theterm“highrate”comesfromtheflowratepersquarefootofsandbed.Iftheflowrateisaboveabout10gpm(37.85L/min), thefilter isclassifiedas“highrate.”Therearesandfilters thatareconsidered“low”or“slow” rate, but they are seldom specified today. Water entersthe filter at the top and is pumped down through the sand toan underdrain manifold with slots narrow enough so that thewaterwillpassbutthesandwillnot.Thewaterispipedtothesandfilterthroughaseriesofvalves(seeFigure3)oramultiportvalve.Amultiportvalveisasingle-handlecontrolwithfourports




thatcanbeconfiguredtoeitherfilter,backwash,rinse,shutoff,bypass,ordrain.Theyarelimitedtofilterswith3-in.(80-mm)orsmallerconnections.Eitherthevalveseriesorthemultiportvalvemaybeautomated.

As the filter accumulates debris, the differential pressureacrossthefilterwillincrease.Whenthedifferentialpressurehasincreasedtoaspecificpoint,normallyabout15psi,thefilterhasreachedthelimitofitseffectivefilterrunandrequirescleaning.Cleaningisaccomplishedbybackwashing.

Backwashingasandfilterisexactlywhatitsoundslike.Back-washing reverses the flow so that the pump now forces waterthrough the underdrain manifold with enough flow to lift thesandbedandstiritaround.Thedebrisisfloatedoutofthesandandflowsouttheinletpipetoadrain.Abackwashsightglassshouldbeinstalledtoallowtheoperatortoseewhentheefflu-entisclear.

Provisionsmustbemadewiththeprojectplumbingengineerifasandfilteristobeused.Manyjurisdictionsrequirethatasandfilterbebackwashedintoasandtraptopreventsandfromenter-ingthesewersystem.Somejurisdictionsrequirethatasandfilterbackwashasanindirectwasteintoapit.Theultimatedestinationofthebackwasheffluentmustalsobedetermined.Somejurisdic-

tionsalloweffluenttoflowtothestorm sewer, others require it togotothesanitarysewer.Provisionmustbemadetohandlethelargeflowratesthatarecustomarywitha sand-filter backwash. Althoughthe backwash only lasts 5 min atmaximum,anenormousamountofwatercanbeusedinthattime.Backwash rates are generally 20gpm/ft2offilterarea.

Ahigh-rate,pressuresandfilterisgenerallysizedat12to15gpm/ft2offilterarea,althoughthefiltermayberatedupto20gpm/ft2.Sizing filters To size a filter,first determine the filtration ratethrough the pool. Once this isestablished, divide the filtrationrate by 0.375 for cartridge filtersor 12 to 15 for sand filters. Thiswilldeterminetherequiredfilterarea.Forfiltrationratesover120gpm (454.25 L/min), dual filtersshould be considered, with theflow divided equally betweenthem. Filters should never besized at their maximum allowedflow rate. This will cause higherpressuredropsthroughthefilterover the filter run and will sub-stantially increase the energyusedbythepump.

PuMPSDisplay pumps Displaypumpscanbethedrytype,theself-prim-ing dry type, or the submers-ible type. When it is necessaryto locate the pump above water

level,aself-primingpumpshouldbeused.Ifthesizeandcostofaself-primingpumpprecludeitsuse,afootvalveorcheckvalvemaybeinstalledinthesuctionline.

Submersiblepumpsaremoreexpensivethandry-typepumpsand may require additional water depth in the pool. This canbe accomplished by providing a pump pit in the water andinstallingafiberglassgratingoverthepit.Thegrateofferspro-tectionfromvandalsandalsohidesthepumpsfromview.Theadvantageofusingasubmersiblepumpisthatitcaneliminatetheneedfor longrunsofpumpsuctionanddischargepiping,thereby saving on horsepower. Since there is less piping andcorresponding friction loss, the required pump head is lower.Insomecases,thiscanmeanasubstantialdifferenceinhorse-power.TheNational Electric Codedoesnotallowsubmersiblepumpsover230Vtobeinstalledinfountains.

Dry-typepumpsareinstalledinavaultadjacenttothepooloramechanicalequipmentroomwithinthebuilding.Thepre-ferredinstallationisonewherethepump-suctioninletislocatedbelowthepool’soperatingwater level.If this isnotallowed,aself-primingpumpmaybeused.Inmostprojects,anend-suc-tion, close-coupled, centrifugal pump is used, but there are

Figure 3 Fountain Components



someprojectswhereahorizontal,split-case,centrifugalpumpisnecessary.Thiscanoccurwheretheflowrateishighandtherequired pump head is low. In all cases, the pump selectionshould be made using the manufacturer’s pump curves. Mul-tiplepumpsinparallelarepreferredtoonelargepump.Redun-dancy, wind control, and opportunities for different displaysareexcellentreasonsformultiplepumps.Somefountainshavedisplaysthatrequirehigh-pressure,low-flownozzles;low-pres-sure,high-flownozzles;andwaterfalldischarges.Wheretherearemultipletypesofdisplay,aseparatepumpingsystemshouldbeusedforeachtype.

Display pumps are sized according to the hydraulic calcu-lations for friction lossandflow rate.Pumps can becast iron,bronzeorplastic.Pumpmaterialsshouldbesuitableforcontactwith fresh water. Since vaults and mechanical spaces are fre-quentlytight,itshouldbepossibletoremovethepumps’motorsandimpellerswithoutdisconnectingthepiping.Pumpsshouldbeequippedwithsuctionbasketstrainerswithremovablebas-kets,suctionanddischargegaugetaps,isolationandbalancingvalves,eccentricandconcentricreducersasrequired,andflex-ible connectors. Proper pump piping practices, as describedelsewhereintheData Book, shouldbefollowed.

To size the display pump the following steps should be fol-lowed:1. Determinethestaticheadrequiredbetweenthelowest

waterlevelandthehighestwaterlevel.Thisisimportantformultilevelfountains.

2. Determinetheheadrequiredatthedischargepoint.Manu-facturersprovidechartsthatgivethegpmandpressurerequiredatthenozzle.Ifthedischargeisforawaterfalleffectwiththedischargepointsubmerged,use10ftofhead.

3. Calculatethefrictionlossinthepiping,fittings,andvalves.

4. Addtheresultstoobtaintherequiredpumphead.

5. Determinethetotalgpmasrequiredforthenozzles,usingthemanufacturer’scharts(orthegpmforaweir,ascalcu-latedusingtheweirlengthanddepth).

6. Selectthepumpusingthemanufacturer’spumpcurves.Iftheexactflowrateandheadcannotbeobtained,selectthenextlargersizepump.Inalmostallcases,thepumpselectedshouldhaveaflatpumpcurve.Selectthemotorthatwillprovideanonoverloadingconditionfortheentirelengthofthepumpcurve.Wide-openconditionsarecommoninwatereffects.

Filter pumps Filterpumpsmaybeofthesametypeasthedis-playpumps.(Seediscussionabove.)Therearefewreasonswhyallthepumpscannotbeofthesametype.

Filterpumpsaresizedtomatchthegpm(L/min)requiredforaproperfiltrationrateandtheheadrequiredtogivethatratewithadirtyfilter.Componentsinthefiltersystemthatcontributetoheadlossinclude:skimmersandmaindrains(pipedinparal-lelsothatthelongestrunmustbedetermined),valves,basketstrainers, face piping (the piping connecting the pump to thefilter),returnpiping,andreturninlets.Elevationchangesneedtobeaccountedforandaddedorsubtracted.Generally,sincereturninletsarebelowthewaterlevel,thereisnonetelevationchange.

Itisimportantthatthepumpbesizedtogivetheproperflowratewithadirtyfilter,butitisalsoimportantthattheengineercalculate the operating point on the pump curve with a clean

filter.Therecanbeasubstantialdifferencebetweenthesetwoconditions in pump flow, and a variable flow-control devicemightbeconsideredforeveningouttheflowrates.Pump strainers and suction screens Asageneralrule,suctionstrainersprotectthepumpsanddischargestrainersprotectthenozzles.Displaypumpsarenotaslikelytopickupwaterbornedebris as are filter pumps, which are connected to skimmersandmaindrains.Provisionscanbemadefordisplaypumpstohavegratingsovertheirsuctionoutletsinthefountain.

Basket strainers on the pump suction protect the pumpfromwaterbornedebris,whichcouldgetcaught intheimpel-ler.Althoughdisplaypumpscanbeprotectedsomewhat fromdebrislargeenoughtodamagethepump,filterpumpsshouldalwayshavebasketstrainers.

Y-typestrainersaremostlyusedtoprotectnozzleswithsmallopenings. They are installed on the discharge side of displaypumpstointerceptwaterbornedebrisbeforeitjamsinsideanactuatorororifice.Thestrainershouldbeequippedwithavalveandhoseconnectiontoallowforeasyblowdown.

Suctiondiffusersareinstalledonthesuctioninlettothepumpandallowforrapidchangesinthedirectionofpipingclosetothe pump. The diffuser slows the water down and straightensitso that itenters thepumpwith less turbulence.Suctiondif-fusersarealsoequippedwithscreensbuttheyareverydifficulttoremoveforcleaningandshouldprobablynotbeusedwhenothermethodsareavailable.

PIPInGAnDVALVESMostpipingforfountainsismadeofSchedule40PVCplastic.Easyhandling,lightweight,andlowfrictionlossesmakeitthepipingofchoiceinmostfountains.AlthoughPVCseemstobetheperfectchoice,therearesomecaveatspertainingtoitsuse.Pipinginstalledthroughpoolwallsandfloorsandintothepoolshouldbecopperorbrass.PVCpipingexposedtosunlightwillbecome brittle, unless it is specifically made to withstand theeffects of ultraviolet rays. Pump suction and discharge pipinginstalledundergroundorwithinabuildingcanbePVCwhereallowed by the local authorities. Be aware that smooth holeshave been found in plastic piping installed underground. TheUniversity of Illinois and the University of Florida both deter-minedthattheholeswerecausedbytermites.TheydonoteatthePVC;theychewthroughitwhenitgetsinthewayoftheircontinuedforagingforfood.Also,beawarethatmostcodesdonotallowplasticpipingtobeinstalledinaplenum.Ductileiron,galvanizedsteelpipe,orstainless-steelpipecanbeusediflargepipesizesarerequiredandPVCcannotbeused.Carbon-steelpipingshouldneverbeusedinafountainduetothehighlyoxy-genatedwaterrunningthroughthepiping.

Allburiedpipingshouldbetreatedasawater-serviceapplica-tion. Specifically, piping needs to be bedded in sand or clean,rock-free backfill. All changes of direction in piping 3 in. (76.2mm)andlargerneedtoberestrainedwithpouredconcretethrustblocks. Starts and stops in fountain systems can cause severewaterhammerandresultantfailureinunrestrainedsystems.

All piping penetrations into the pool wall should be waterstoppedinsomefashion.Acommonmethodistousea“puddleflange” attached to the pipe itself. For penetrating walls intomechanical rooms, a mechanical pipe seal can be used. (SeeFigure4.)

Unions or flanges should be used at the final connection toallequipmentsothattheequipmentcanbeeasilyremovedfor




repairs.Drainagelinesfromtheoverflowanddrainlinesshouldbe either PVC or cast iron, as required by local code. Watermakeupandfill linesshouldbecopper tubing.Differentmetalpipes carrying water or installed underground must not comeintocontactwitheachother(dielectricisolation).

All piping systems should be pressure tested immediatelyafterinstallation,andthetestshouldbeleftonuntilthepipingis ready to be connected to the inlet and outlet devices andequipment.Thisway,aglanceatapressuregaugecanindicateimmediatelyifapipehasbeenbrokenduringanotherphaseoftheconstruction.Thetestpressureshouldbelimitedto50psi(344.74 kPa), since the fountain piping systems are operatedat relatively low pressures. If the system requires higher pres-sure,thepressuretestshouldbemadeatapressurethat is25psi(172.37kPa)higherthantheoperatingpressure.Makesurethatplasticpipingistestedwithinthepressuresrecommendedbythemanufacturer.

Prior to connecting the devices and equipment, piping sys-tems should be flushed and cleaned. Caps should be left onuntilreadytomakethefinalconnectiontopreventdebrisfromenteringthepiping.Morethanonepumphasbeendamagedorhadreducedflowduetodebristhatwasinthepipebeforethepumpwasconnected.Suction-line piping Size the suction line at a velocity not toexceed6fpsforcopperpipingand10fps(3.05m/s)forplasticpiping. Provide a suction inlet designed so that the drain willnot trap a person in the pool. This is accomplished by havingdualdrainsspacedat least4 ftapartordualdrains located indifferentplanes(suchasabottomdrainandasidewalldrain)orbyusinganti-vortexdrains.Somemeansofpreventingvor-texingshouldbeusedtopreventcavitationof thepumps. Ifaminimumof18in.(457.2mm)ofwatercannotbeprovidedoverasuctiondrain,sizethedrainfor½ofthemanufacturer’srec-ommendedmaximumflowandaddmoredrainsasnecessary.Suction-linepipingshouldbe installedwithoutvertical loops,whichcanbecomeairbound.Inaddition,itiscriticalthatsuc-tion piping pass a 25 psi (172.37 kPa) pressure test because avoidassmallasapinholecanpreventaself-primingpumpfrompumping.Return piping Return piping should be sized at 6 fps maxi-mumforcopperpipingand10fpsmaximumforplasticpiping.Return piping, especially piping close to the discharge of the

pump,shouldbeproperlybracedwithinthemechanicalroom.Fire-protectionbracingmethodsmaybeused.Returnpipingtomultiple inlets (nozzles, etc.) must be hydraulically balanced.Filterreturnpipingterminatesineitheradjustableornonadjust-ablereturnfittings.Returnfittingscanbewallorfloormountedand should be adjusted to direct flow to the main drain andskimmers.Deadspotsshouldnotbeallowedinapool.Hydraulic balancing Suction and return headers should behydraulically balanced as closely as possible to ensure evenflow throughout the fountain. (See Figure 5.) For applicationswherethefountaincanbeencircledbyaheader,thisprovidesan excellent balancing tool. Nozzle patterns and return inletheaderscanbesizedusingthefollowingequation:

Equation 1qn=2.45C(D2)(2ghn)

where qn=Dischargefromorificen,gpm(L/min)2.45 =Conversionfactorusedtoexpressthedischargeingal/

min(L/min)whenthediameterisexpressedininches(mm)andthevelocityisexpressedinfps(m/s).

Figure 4 Wall Penetrations

Figure 5 Hydraulic Balancing



C =Orificedischargecoefficient(usually=0.61forholesdrilledinthefield)

D=Diameteroforifice,in.(mm) g =Accelerationduetogravity,32.2ft/s2(9.81m/s2) hn=Headonorificen,ft.(m)

Theheadonorificenisequalto:

Equation 2

hn= [ 1 ] qn2

(2.45CD2)22g= kqn

2

= k(mq1)2

= m2h1

where k =Constant h1=Headonorifice1,ft(m) m=Massflowrate

Theheadlossbetweenorifice1andn,whichcorrespondstotheheadlossinthedistributionpipebetweenorifice1andn,is:

Equation 3∆h(1–n)=h1–hn

Nowitcanbeshownthattheheadlossbetweenthefirstorificeandthelastorificeinadistributionpipewithmultiple,evenlyspacedorificesisapproximatelyequaltoone-thirdoftheheadlossthatwouldoccurifthetotalflowweretopassthroughthesamelengthofdistributionpipingwithoutorifices.Thus,

Equation 4hfdp= 1⁄3hfp

=∆h(1–n)

where hfdp=Actualheadlossthroughdistributionpipe,ft(m) hfp=Headlossthroughpipewithoutorifices,ft(m)

The head loss through the pipe can be computed using theHazen-Williamsequation:

Equation 5hfp=10.5(L1–n) Q 1.85D–4.87

Cwhere hfp=Headlossthroughthepipefromorifice1toorificen,ft

(m)L1–n=Lengthofpipebetweenorifice1andn,ft(m) Q=Pipedischarge,gpm(L/min) C=Hazen-Williamscoefficient(150forplasticpipe) D=Insidediameterofpipe,in.(mm)

Thedifferenceindischargebetweenorifice1andnforagivendistributionpipeandorificesizecannowbedeterminedusingEquations5-1through5-5.Ifthecom-puted value of m is too low (<0.98),the size of the distribution pipe canbe increased. The percent differencein flow between 1 and n will be [(1–n)×100].Agoodvaluewouldbelessthan2%.Valves

Shutoff valves Most valves forfountains are of a type that allows

throttling.Sinceadjustingthefountainisverysubjective,almosteveryvalveinthesystemcouldbeinvolvedinthefinaladjust-ments.Thislimitstheselectiontoball-and-globevalvesforthesmallerpipeandbutterflyvalvesforthelargerpipe.Lug-type,butterflyvalvesarenormallyusedinapplicationswhereequip-mentneedstobedisconnectedwhilestillunderwaterpressure.Apumproomthatismuchlowerthanthefountainwillbebestservedbylugvalvesattheequipmentconnectionssothattheequipmentcanbeservicedwithoutdrainingthefountain.

Check valves There are several types of check valve, butmostareoftwotypes:gravityandspringloaded.Thegravity,orswing-check, valve must be installed in a prescribed manner.Thegravitycheckshouldbeinstalledwherewaterpressurewillhelp provide a positive closure. Where a check valve must beinstalledonahorizontalline,aspringcheckshouldbeinstalled.A footvalve isaspecial typeofcheckvalvethat is installed inthepump-suctionline.Thepurposeofafootvalveistopreventthesuction line fromdrainingback into thepoolandcausingthepumptoloseprime.Avalvedlinefromthemakeupsystemshouldbeinstalledbetweenthepumpandthefootvalvetoaidinpriming.Itwouldbeprudentalsotoinstalladraininthatsec-tionofpipe.

Pressure-regulating valves Dynamicfountainsaredesignedusingpressure-regulatingvalves.Theregulatingvalvemaintainsa selected downstream pressure regardless of the changes intheupstreampressure.Therefore,whenthesprayheightofonesetofnozzlesisraisedorlowered,theregulatingvalvekeepsasecondsetofnozzlesatthesamesprayheight.

Actuator-control valves In addition, actuator-controlled,motorized,orpneumaticvalvescanbecontrolledusinga4to20-milliamp (mA) electrical signal. The valve can be set to befully closed at 4 mA and fully open at 20 mA. At any point inbetween,thevalvewillbeopenanamountcorrespondingtothepositionofthepointwithinthisrange.Forexample,at6mA,thevalvewillbeslightlyopenandat15mAitwillbealmost fullyopen. A computer can be programmed to provide signals toopenandclosethevalvesinanypatterndesired.Materials AsamplescheduleofpipingmaterialsisshowninTable1.

DISCHARGEDEVICESManyreturnmethodsareusedtoreturnthewaterintothepool.Thedesignermustchoosewhichmethodeithercreatestheleastdisturbance to the desired water effect or creates the desiredwatereffect.Weir pools Commonmethodsofreturnintoupperweirpoolsare:diverterplates(oftenanti-vortexdrainsusedonthereturnside),wellscreens,anddoubletees.(SeeFigure6.)Spray jets Numerous typesofnozzlearemanufactured.Thedesignershouldselectthetypeofthatwillprovidethedesired

table 1 Sample Schedule of Materials

SystemIndoor/Outdoor

Abv/Blw Grade

Size, in. (mm) Pipe Material Fittings Joints

Static display piping Either Either ½–24 (12.5–600)

Sch. 40 PVC Socket Solvent weld

Dynamic display piping Either Either ½–16(12.5–400)


Filtration piping Either Either ½–24(12.5–600)


Makeup water Either Either ½ –4(12.5–100)

Type L copper Wrot copper Solder

Makeup water Either Either 6+ (150+) Type 302 stainless steel

Type 302 stainless steel

Mechanical groove




sprayeffect.Thiscanonlybedonebyreferringtothedatalistedin the manufacturer’s catalogs. Nozzles are available to pro-vide solid or aerated columns of water, pyramid-like columnsofwater,aeratedmoundsofwater,mushroomshapes,floatingdandelioneffects,fan-shapedsprays,finger-likefansprays,bell-likeshapes,twirlingjets,andnumerousothereffects.

Allaeratingjetsofvarioustypesfallintotwocategories:water-level dependent and water-level independent. The water-leveldependenttypeofjetreliesonthewaterlevelinthepoolbeingconstant.Thisconstantlevelallowsthejettoaspirateairintothewatertogiveapleasing,frothingeffect.Thereisarangeofdepths

formostmanufacturer’sjetswithazoneof1-2in.whereinthejetwillfunction.Thesejetsareslightlylessexpensivethantheindependenttypebutrequirethatthelevelbemaintainedveryaccurately.Usingjetsinapoolthatemptiesoveraweirisaverygoodapplicationofthisjet.Usingjetstosurroundageyserthateruptseveryfewsecondsisnotagoodapplication,asthewaterwillsurgeagreatdeal.Inthelattercase,awater-levelindepen-dentjetwouldbetheanswer.

COnTROLSRemote control Display pumps and filter pumps should becontrolled from a point within view of the fountain. This canbe achieved with a remote, hard-wired control panel and keyswitchesoraradiosignal.Radioremote-controlunitsthatcon-trol several separate electrical loads by means of a hand-heldtransmitterandamanualswitchingpanelareavailable.Theseenableadoormanorconciergetoquicklyshutdownthefoun-tainintheeventofaproblem,suchassomeonejumpingintothefountain.Pump starters Allpumpsshouldhavestarterswithoverloadprotectiontoprotecttheirmotors.Adisconnectswitchmustbeinstalled within view of the pump. The engineer should verifythat these itemsareprovidedforunderthescopeofelectricalwork.Wind controls Windcontrolsreducetheheightofafountaindisplayorshutoffthedisplaypump.Atime-delayrelaykeepsthepumpoffforat least3mintoavoid theproblemofpumpcycling. Three methods are used to reduce the height of thefountaindisplay:1. Thewindcontrolopensorclosesasolenoidormotorized

valve,therebybypassingwaterfromthenozzlesbackintothepoolandreducingthesprayheightofthenozzles.Thevalveandbypasslinemustnotbeundersized,ortherequiredflowwillnotbebypassed.

2. Apressure-regulatingvalvecanbeinstalledinthedischargelineofthedisplaypump,andareduced-pressuresettingisusedtolowerthesprayheight.Thismethodissomewhatmoreexpensivethanthebypass-controlvalve.

3. Ifthedisplaypumpsconsistoftwoormorepumpsinparal-lel,shuttingdownapumpwillreducetheheightbyslightlylessthantheproportionalamountproducedbytheshutdownpump.Reducedfrictioninthedischargelinewillslightlyincreasethedischargeoftheremainingpump.

Withallthesemethods,hydrauliccalculationsarerequiredtodetermine that thecapacitiesand friction lossesareadequatetoachievethedesiredeffect.Atwo-stagewindcontrolisoftenused,inwhichthefirststagereducestheheightofthedisplayandthesecondstageturnsthesystemoffcompletely.Time switches Various types of time switches are available,from electric motor operator to electronic. Time switches canbeusedtooperatethepumpsatthedesiredtimes.Inaddition,cycle timerscanbeusedto turnsolenoidvalvesonandoffatpresetintervalsof5sormore.Pressure and flow switches Pressure and flow switches areused to shut pumps off in the event that the pressure or flowdropstoolowinthepumpdischarge.Theyarealsousedtosignalwater-treatmentsystemsofflow/noflowconditions.Start/stopswitchesareequippedwithtime-delayrelaystoallowthepumptobestartedandalsotokeepthepumpoffforaprogrammabledelaytopreventpumpcycling.

Figure 6 Discharge Devices

0 PlumbingSystems&Design MAY/JUNE 2006 PSDMAGAZINE.ORG


LIGHTInGLightsareavailableinlow-voltageaswellasnormallinevoltage.Somejurisdictions,suchastheCityofNewYork,requireonlylow-voltagelightingandapprovalofalllightsandtransformersusedinthe jurisdiction.Most lightscanbeobtainedwithcol-ored lenses ifdesired.Rockguardsarerequired.Maintainthewaterleveloverthelightsasrequiredbythemanufacturer.TheNational Electrical Code(NEC)mustbefollowedwheninstall-ing underwater lights, transformers, and submersible pumps.Allelectricalsystemsthatsupplypowertoequipmentorlightsinthepoolmusthaveground-faultinterruptercircuitbreakers.

Fountain lights should be installed directly under the waterdisplaytoilluminatethegeneralpoolareaaswellasthewaterdisplay. The number of lights and the wattage depend on theoverallsizeof thepool, theheightandwidthof thewaterdis-play,andpossibleinterferencefromambientlighting.

Free-standinglightsarewiredthroughabronze,underwaterjunctionbox.Theboxmustbelistedbyanationallyrecognizedtestingagencyandapprovedforunderwateruse.Thecablefromthe light is fed through a compression seal that is connectedto the junction box. When the architect wants to conceal thecable,thecableisfedthroughacompressionsealtoanadjacentbrassconduittoaremotejunctionbox.Thecablemustbelongenoughtoreachtheremotejunctionboxwithoutsplices.

Niche lights that are installed in pool walls have conduitdirectly connected to the niche and extended to a remotelylocatedswitchbox.Thecablemustbelongenoughtoreachtheremotejunctionboxwithoutsplices.

Lights are usually controlled by either astronomical timeswitchesorregulartimeswitchesandaphotocell.Itisadvisabletodesignthecontrolsystemsothatmaintenancepersonnelarenotrequiredtoadjust the light timers fordaylightsavingstimeandchangingsunsettimes.

In general, selecting colors forthe lights should be done with carebecause of the subjective naturewith which each person views thefountain. If blue, red, amber, andotherdarkcolorsareused,thelightsshouldhaveahigherwattage.

WATERHEATInGEquIPMEnTIf a fountain is to be kept in opera-tion during the winter months anditispossibleforthewatertofreeze,a pool water heater should be pro-vided. The pool heater can be asteam heat exchanger, a hot-waterheat exchanger, an electric waterheater, or a gas-fired water heater.Theheatershouldbesizedtomain-tainthepoolwaterataminimumof35°F(1.67°C).

Overall heat loss due to surfaceevaporation, radiation, conduction,and convection for concrete poolswherethewatertemperatureis35°F(1.67°C) and the air temperature is10°F(–12.2°C)canbeobtainedasfol-lows:• 25 mph wind velocity

TotalBtu/hheatloss=[203×surfaceareaofthepoolinft2

(m2)]+[34×sidewallareainft2(m2)]

• 20 mph wind velocity



• 15 mph wind velocity



It is also necessary to include the heat loss from the piping.Select a heater with an output equal to the Btu/h heat loss. Inmanylargebuildings,theheatingmediumcanbetheheatinghotwaterorsteam.Theheater iscontrolledbyatemperaturecon-trolwiththesensingbulblocatedintheinletpipetotheheater.Thecontrolwillturnontheheateriftheincomingwaterfromthepool isbelow35°F(1.67°C)andshut itoff if the temperature isabove37°F(2.78°C).Aflowswitchintheinlettotheheaterwillpreventoperationoftheheaterifthereisinsufficientornoflow.Theheatershouldbelocatedonabypassline,asshowninFigure7.Thepipingwithin3ftoftheheatershouldbeTypeLcoppertubing.

WATER-TREATMEnTSySTEMA properly engineered water-treatment system will allow theoperatortomaintainasparklingclear,odor-andalgae-freepool.Certain water-treatment methods should be engineered intothesystemandcertainwater-treatmentmethodscanbeadmin-isteredbytheoperator.Water-treatmentparametersinclude:1. Disinfectant residual—measuredinpartspermillion(ppm).

2. Oxidation reduction potential (ORP)—ameasureofthecleanlinessofthewater.Measuredinmillivolts(mV).

3. pH—ameasureoftheacidityorcausticityofthewater.

Figure 7 Piping Schematics

MAY/JUNE 2006 PlumbingSystems&Design 1



4. Alkalinity—ameasureoftheresistanceofthewatertochangeinpH,adimensionlessnumber.

5. Total dissolved solids—ameasureofthetotaldissolvedsolidsinthewater,measuredinppm.

6. Calcium Saturation Index (CSI) or Langelier’s Index—adimensionlessnumber.

7. Cyanuric acid level—Cyanuricacidisusedtopreventthedissipationofchlorinebysunlight.Itisalsotoxicathigherlevels.Measuredinppm.

Engineeredsystemsinclude:1. Mechanical filtration—sandorcartridgefilters,which

removeparticulatesfromthewater.

2. Disinfection systems—includingchlorineandbrominefeed-ersandozone.Providecontroloforganicsandalgae.

3. pH control systems—gaseousCO2contacttanksandacid/basefeeders.

4. Oxidation reduction potential (ORP) monitors—provideanoverallmeasureofthecleanlinessofthewater.

Operator-administeredtreatmentsinclude:1. Water chemistry—Althoughsomechemistriescanbedone

electronically,mostmustbedonebytheoperatorandthedatarecorded.

2. Shock or hyperchlorination—usedtodestroychloraminesformedwhenchlorinedestroysorganiccompoundsinthewater.Chloraminesgivepoolsthatdistinctivechlorinesmell.Amassivedoseofchlorine(10ppm)willdestroythechloramines.

3. Dechlorination—Aftershocktreatments,thewaterisoftendechlorinatedwithsodiumthiosulfate.

4. pH adjustment—DifferentchlorinecompoundswilleitherraiseorlowerthepH.Gaseouschlorine(rarelyused)willlowerthepHandsodaashwillneedtobeadded.PowderedorliquidchlorinewillraisethepHandmuriaticacidwillhavetobeadded.

Althoughproperwaterchemistryisimportantfromadisinfec-tionstandpoint,resultinginanalgae-freepool,waterbalanceisequally important.TheCalciumSaturationIndexorLanglier’sIndexisameasureofthecorrosivenessofthewater.IftheCSIisbelow0,thewateriscorrosiveandwillstarttocorrodethepoolwalls, fittings, and equipment. If the CSI is above 0, the waterissaturatedandwillbegintoplateoutcalciumdepositsonthepoolwall,fittingsandequipment.

Disinfection inreflectingpools isnecessary tocontrolalgaeandtodestroyorganicsinthewater.Commonmethodsofdis-infection are chlorine, bromine, and ozone. Chlorine can beused indoors or out with equal success. If used outdoors, thechlorineshouldbecombinedwithcyanuricacidasastabilizer.Thecyanuricacidwillenablethechlorinetolastmuchlongerindirectsunlight.Bromineisnotrecommendedforoutdoorpoolsbecausethereiscurrentlynowaytostabilizeitanditdissipatesrapidly.

Chlorine comes in three forms: gaseous, liquid, and solid.Gaseous chlorine is the most efficient method of delivery butcanbeverydangerouswhenmishandled.Liquidchlorineisthepreferredmethodwhendealingwithmultiplebodiesofwaterorasinglebodyofwaterinexcessof75,000gal(283905L).Achemical proportioning pump and 50-gal (189.27-L) chlorinesolutiontankisusedtoadministerthedisinfectant.Theinjec-

tionpointshouldbedownstreamofthefilter.Solidordrychlo-rinecomesinmanyforms:solidpellets,granular,orpowder.Itisadministeredusinganerosionfeederthatisinstalledinparal-lelwiththefilterandworksonthedifferentialpressureacrossthefilter.

Caution: Two types of dry chlorine, sodium hypochloriteandcalciumhypochlorite,arebothcurrentlyused.Ifthesetwocompoundsaremixedtogether,aviolentexplosioncanresult.Chlorineusevariesfrom1to5oz/day/1000gal(0.03to0.15L/day/3785.4L),dependingonthetemperatureofthewaterandtheamountofsunlight.Bothwarmwaterandsunlightdissipatechlorinerapidly.

Ozone is an excellent method of disinfection for water butdoeshavelimitations.Theozonegasshouldbeappliedinacon-tacttankandtheoffgasfromthetankshouldbedirectedtoanunoccupiedarea. Inaddition,ozonedoesnot leavearesidualinthewater.Asmallchlorinefeedershouldbeaddedtopoolsreceivingahighorganicload,suchasoutdoorpools.Asafinalnote,certainmanufacturerswillnotwarrantytheirproductsforuseinanozone-treatedpool.

MAKEuP-WATERSySTEMThe fountain should be provided with both a manual andan automatic fill system piped in parallel (see Figure 8). Themanualfilllineshouldbeatleast1½to2in.(40to50mm)andtheautomaticfilllinebe¾in.(20mm)forsmallandmediumfountainsandaslargeas4in.(100mm)forlargefountains.Agood rule is to determine the makeup-water rate for coolingtowersinthearea.Theinformationshouldbeingpm(L/min)ofmakeupwaterpergpm(L/min)ofcondenserwater.Thiswilltranslatedirectlytogpm(L/min)ofmakeupwaterpergpm(L/min)ofeffectwater.Forreflectingpools,thelocalwaterauthor-ity should have information regarding evaporation rates fromswimmingpools.Whendesigningthemakeup-watersystem,itmaybeadvantageoustoconnectthemakeup-waterlinetothefilter-pumpsuctionline.Ifthisisdone,makesurethattherearenovalvesbetweenthemakeup-waterinletandthepool.Thisistoensurethatthefiltersystemdoesnotbecomepressurizedtodomestic-waterlinepressure.Mostpoolequipmentisnotbuilttowithstandthehigherpressure.

Inallcases,backflowpreventersarerequiredonmakeup-waterpipingtofloatvalves.Theyarealsorequiredonsolenoid-oper-ated,makeuplinesunlesstheinletpipeisatleast2pipediam-etersormoreabovethepoolwall.Verifyallmethodsofbackflowpreventionwiththelocalauthorityhavingjurisdiction.

Multilevelpoolsrequirethatawater-levelsensor(notafloatvalve) be located in the lowest pool and the makeup inletbe located in the highest pool. Low-water cutoff sensors arerequiredinthelowestpooland,iftheunderwaterlightsdonothave individual low-water cutoffs, then every pool level musthavealow-watercutoff.

Figure 8 Makeup-Water Devices



Makeup-Water DevicesStilling wells or chambers Stillingwellsorchambersarean

importantpartofanymakeup-watersystem.Withastillingwell,thelevelinthewellisanaccuraterepresentationofthelevelinthe pool. The advantage to the stilling well is that it remainsrelativelycalminsidethewellanddoesnotreflectthesurfacedisturbancesthatmayoccurinthepoolitself.Astillingwellcanalsoincorporateanoverflowdrain.

Mechanical methods Mechanical water makeup is thecheapestmethodandisleastpronetomaintenanceproblems.In this method, a float valve installed in the wall of the poolprovidesautomaticmakeup.Thetopofthepoolwatermustbeatleast5in.abovethewaterlevelforthefloatboxtofitinthepoolwall.Amethodofremotelymaintainingthewaterlevelistoinstallafloatvalveinanopentankorconnectedtothepoolbyapipeandrootedtoaremotelocation.Thereshouldbenoconnectiontothispipeexceptforavalveddrain.Withthepipeopenateitherend,thewaterlevelinthetankwillbethesameasthewaterlevelinthepool.Theproblemencounteredwiththisapplicationisfindingalocationforthetank.

Anothermethod,commonlyusedonlargepools,usesapilot-operated makeup valve. With this method, a small float valve isinstalledinastillingwellandthepilotwaterforthelargervalveisroutedthroughit.Whentheleveldrops,thepilotfloatvalveopensandwaterisallowedtoopenthelargervalve.Theadvantagetothismethod is that a small stilling chamber can be located near thepoolwhilethelargervalvecanbelocatednearthepumpsinthemechanicalroom.

Electrical method Where the above methods cannot beused,watermakeupcanbeprovidedbyusingelectricalsensorsthatopenorcloseasolenoidvalveonthemakeup-waterline.Amanualfillvalveisordinarily installedinabypassaroundthesolenoidvalve.Thesensorsuselowvoltageorinducedvoltagethatprecludesanyelectricaldanger.Sensorsthatutilizeareedswitch,activatedbyapermanentmagnet,arealsoavailable.Thesensorscanbemountedinthewallofthepool,accessiblefromthefront.(SeeFigure9.)Theycanalsobelocatedinthetopofthewallwiththesensorshangingdownintoa1¼-in.(32-mm)brass pipe that has an air vent and a horizontal leg extendingintothepoolwater.Whereitisnotfeasibletomountthesensorsinthepoolwall,theycanbelocatedanywhereinthepoolwaterbymountingthesensorboxontopofabrassconduitwhereverit enters the pool. The sensor will generate a small amount ofcurrentfromthesensortip,throughthewaterandintothebrasspipe.Ifwaterisnotpresent,thecurrentflowstopsandthecon-trolpanelopensthesolenoidvalve.Brasspipingmustbeusedas it provides the electrical ground path. Electrical wiring hastobeextendedtothesensorsinthepoolareaaswellastothecontrolpanelandthesolenoidvalve.

Dualsensorsareavailablethatwillprovideforwatermakeupandlow-watercutoff(sothatpumpswillbeshutoffintheeventoflowwaterlevel).Theycanalsoshutofftheunderwaterlights,which can be damaged by operation without adequate watercover.

OVERFLOWAnDDRAInAGESySTEMOverflow drains Overflow drains are required for two rea-sons:toprovideameanstoremovewaterifthemakeup-watervalve malfunctions and to provide a means to remove stormwaterandmaintainafixedwaterlevelsothatnozzleswillworkproperly.Thesizeofanoverflowdrainforanindoorpoolshould

be 2 in. If the makeup-water line is larger than 1 in., increasethesizeoftheoverflowdraintopreventflooding.Sizingforanoutdoorpoolshouldbebasedontheareaofthepool,inft2(m2),asrequiredbythelocalplumbingcodeforstormdrainage.

The preferred location for an overflow drain is in the poolwall,becauseit islessobtrusivethere.Therearetimesthoughwhenthepoolwallisinsufficientfortheinstallationofanover-flowdrain.Insuchcases,aremovableoverflowstandpipecanbeprovided.Adomeorscreenshouldbeplacedontopofthestandpipe.Theoverflowdrainalsoactsasthemaindrainwhenthe standpipe is removed. Overflow standpipes are subject tovandalism and should be located so that they are not easilyaccessible to thepublic.Anothermethod is to installanover-flowpipeonabypassaroundamaindrainvalve.Theoverflowpipeinvertmustbeslightlyhigherthanthehighwaterlevelandhaveanairopeningtopreventsiphonage.Emergency drains Emergency drains are needed to drainthepooliftheoutsidetemperaturedropsbelowfreezing.Thisisachievedbyprovidinganaquastatthatcontrolsasolenoidvalvelocatedinthedrainline.Theaquastatshouldbesettoopenthesolenoid valve if the temperature drops too low. The solenoidvalvemusthaveamanualoverrideintheeventofapowerfailureandmustnotrequiredifferentialpressuretoopenthevalve.AnOngontzvalveisanotheremergencydrainvalvethatmechani-callystartstoopenwhenthetemperaturedropsto38°F(3.33°C)and fully opens at 34°F (1.11°C). In the above cases, electricalsensors, as described above under “Makeup-Water Devices,”shouldbeprovidedtoshutofftheelectricalpowertothepumpsandlights.Themakeup-watervalveshouldbewiredtocloseiftheemergencydrainvalveisopen.Itmayalsobeadvisabletohaveanalarmringto indicatethattheemergencydrainvalvehasopened.

REFEREnCES1. AmericanNationalStandardsInstitute/NationalSpaand

PoolInstitute.1991.Standard for public swimming pools, ANSI/NSPI-11991.Alexandria,VA:NationalSpaandPoolInstitute.

2. Kowalsky,L.1990. Pool/spa operators handbook.SanAnto-nio,TX:NationalSwimmingPoolFoundation.

3. Tchobanoglous,George,andFranklinL.Burton.1991.Wastewater engineering: Treatment, disposal, and reuse.3ded.NewYork:McGraw-Hill.

Figure 9 Electronic Makeup-Water Device



COnTInuInG EDuCaTIOn

1. The filtration turnover rate in a reflecting pool or fountain is determined by _______.a. the local codeb. the architectc. the engineerd. the color of the water desired

. Surge collars are used to minimize _______ in circular pools.a. discolorationb. plant growthc. evaporationd. waves

. The water treatment system should maintain _______.a. sparkling clean waterb. odor-free waterc. an algae-free poold. all of the above

. When a fountain is to be operated in freezing conditions, the water should be heated to maintain _______ degrees fahrenheit minimum.a. 10b. 35c. 40d. all of the above

. The university of Illinois and the university of florida have determined that the smooth holes found in underground PVC pipe are caused by _______.a. exposure to ultraviolet raysb. exposure to sunlightc. termitesd. high velocity

. The headers indicated in fig. may have their orifices balanced using _______.a. equations 1 through 5b. the average percentage indicatedc. good engineering practiced. looped piping around the fountain

. all pumps serving the pool and/or fountain should be located to ensure _______.a. they are higher than the pool or fountain for

maintenance purposesb. they are lower than the pool or fountain to maintain

a flooded suction linec. that they can be viewed by the publicd. none of the above

. The most common types of weirs are _______.a. metal edgeb. upward taperedc. rounded edged. all of the above

. Oxidation reduction potential (OrP) is _______.a. controlled by the pHb. a measure of the total dissolved solids in waterc. controlled by the operatord. a measure of the cleanliness of the water

10. reflecting pools and fountains provide _______.a. a place to grow water plantsb. a retreat area in which to rest and relaxc. a place to fishd. a place for frogs to play

11. hydraulic balancing of the suction and return headers is required _______.a. to ensure even flow throughout the fountainb. by local codesc. to keep sound levels lowd. all of the above

1. When using a sand filter, what flow rate and above, in gallons per minute, will classify it as a high-rate filter?

a. gpmb. 4 gpmc. 8 gpmd. 10 gpm

Doyoufinditdifficulttoobtaincontinuingeducationunits(CEUs)?Is it hard for you to attend technical seminars? Through PlumbingSystems&Design(PS&D),ASPEcanhelpyouaccumulatetheCEUsrequired formaintainingyourCertified inPlumbingDesign(CPD)status.

ASPEfeaturesatechnicalarticleineveryissueofPS&D,excerptedfrom its own publications. Each article is followed by a multiple-choicetestandasimplereportingform.

Readingthearticleandcompletingtheformwillallowyoutoapplyto ASPE for CEU credit. For most people, this process will requireapproximately1hour.Anominalprocessingfeeischarged—$25forASPE members and $35 for nonmembers (until further notice, thememberfeeiswaived).Ifyouearnagradeof90%orhigheronthetest,youwillbenotifiedthatyouhavelogged0.1CEU,whichcanbe

appliedtowardtheCPDrenewalrequirementornumerousregula-tory-agencyCEprograms.(Pleasenotethatitisyourresponsibilitytodeterminetheacceptancepolicyofaparticularagency.)CEUinfor-mationwillbekeptonfileattheASPEofficefor3years.

Nocertificateswillbeissuedinadditiontothenotificationletter.You can apply for CEU credit on any technical article that hasappearedinPS&Dwithinthepast12months.However,CEUcreditonlycanbeobtainedonatotalofeightPS&Darticlesina12-monthperiod.

Note:IndeterminingyouranswerstotheCEquestions,useonlythe material presented in the continuing education article. Usingotherinformationmayresultinawronganswer.


CE Questions—“Reflecting Pools and Fountains” (PSD 133)



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PSD

139

Private Sewage Disposal Systems


MAY/JUNE 2007

PSDMAGAZINE.ORG


With the ever-increasing cost of land located in proximity to urban centers, more and more construction is being imple-mented in outlying areas. Sanitary sewers are not usually avail-able in these remote locations and it becomes necessary for the plumbing engineer to design private sewage systems to handle the wastes from buildings. Before the rapid escalation of land values, most private sanitary disposal systems were used almost exclusively for private residences. It is estimated that 15 mil-lion such systems are presently in use in the United States. Of greater significance, roughly 25% of all new home construction now employs the septic tank–soil absorption sewage disposal system.

Where the concentration of population is not sufficient to economically justify the installation of public sewer systems, installation of a septic tank in conjunction with a subsurface soil absorption field has proven to be an exceptionally satisfactory method of sewage disposal. When properly designed, installed, operated, and maintained, it compares very favorably with the most sophisticated municipal sewage treatment plants.

In 1946, the U.S. Public Health Service, in cooperation with other federal agencies involved in housing, embarked upon a five-year study to establish criteria for the design, installation, and maintenance of the septic tank. Most of the information in this chapter is freely drawn from that study and a later report issued in 1967.

Sewage SyStem CriteriaThe proper disposal of sewage is a major factor affecting the health of the public. When improper or inadequate disposal of sewage occurs, many diseases, such as dysentery, infectious hepatitis, typhoid, paratyphoid, and various types of diarrhea are transmitted through contamination of food and water. To avoid such hazards, any system of sewage disposal must meet the following criteria:• It must not contaminate any drinking water supply.• It must not be accessible to insects, rodents, or other

possible carriers that might come in contact with food or drinking water.

• It must not be accessible to children.• It must not violate laws or rules and regulations governing

water pollution or sewage disposal.• It must not pollute or contaminate the waters of any bath-

ing beach, shellfish breeding ground, or any stream used for public or private water supply or for recreational pur-poses.

• It must not become malodorous or unsightly in appear-ance.

All these criteria are admirably fulfilled by a public sewage dis-posal system. Every effort should be made to utilize such facili-ties if at all possible. When public sewers are not available, some other satisfactory method must be employed.

Any method of sewage disposal is merely an attempt to com-plete the hydrologic cycle, or as it is now popularly called, the ecological cycle. Contaminated water (wastes) of undesirable quality is received and, after processing, returned at an accept-able level of quality. The systems to be discussed are those that return the waste water to the soil and ultimately to the ground water (water table).

There are presently two systems that return waste water to the soil. They are the cesspool and the septic tank–soil absorption systems.

CeSSpoolSA cesspool is nothing more than a covered pit with an open-jointed or perforated lining into which raw sewage is discharged. The liquid portion of the sewage is disposed by seepage or leach-ing into the porous soil surrounding the cesspool. The solids (sludge) are retained in the pit.

A cesspool finds its greatest application in receiving the efflu-ent from one-family homes and it is not recommended even for this use. The raw sewage tends to seal the openings in the pit lining as well as the surrounding soil, thus necessitating fre-quent visits from the “honey dippers” (cesspool cleaning ser-vices). Cloggage may become so severe that complete abandon-ment of the existing cesspool and the construction of a new pit is often necessary. A cesspool should never be recommended as a substitute for a septic tank with a soil absorption field.

A seepage pit (discussed in another portion of this chapter) should never be confused with a cesspool. Although the con-struction is the same for both, a seepage pit receives the efflu-ent from a septic tank (where the solids have been liquified), whereas a cesspool receives raw sewage.

SeptiC tankSA septic tank is a liquid-tight structure, with inlet and outlet connections, which receives raw sewage. It is basically a sewage settling tank in which raw sewage is retained for a specified period of time, usually 24 hr. The primary purpose of the septic tank is to act as a settling tank and to break up solids so that the resulting effluent will not clog the pores of the soil in the leach-ing field. Very little purification is accomplished in the tank; the actual treatment and digestion of harmful waste materials takes place in the ground after discharge from the tank.

Three functions are performed by a septic tank to produce an effluent suitable for acceptance by a subsoil absorption system of sewage disposal: (1) removal of solids, (2) biological treat-ment, and (3) sludge and scum storage.

removal of SolidSClogging of the soil varies directly with the amount of suspended solids in the liquid. The rate of flow entering the septic tank is reduced within the tank so that solids sink to the bottom or rise to the surface of the liquid in the tank. These solids are retained and the clarified effluent is discharged.

Private SewageDisposal Systems

Reprinted from Engineered Plumbing Design II, Chapter 21: “Private Sewage Disposal Systems,” by A. Calvin Laws, PE, CPD.© American Society of Plumbing Engineers.

Plumbing Systems & Design MAY/JUNE 2007 PSDMAGAZINE.ORG



Solids and liquid in the tank are exposed to bacterial and natural processes, which decompose them. The bacteria pres-ent in the wastes are of the anaerobic type, which thrives in the absence of oxygen. Decomposition of the sewage under anaer-obic conditions is termed “septic” and it is from this the tank derives its name.

After such biological action, the effluent causes less clogging of the soil than untreated sewage containing the same quantity of suspended solids.

Sludge and SCum StorageSludge is an accumulation of solids at the bottom of the tank. Scum is a partially submerged floating mat of solids that forms at the surface of the liquid in the tank. The sludge is digested and compacted into a smaller volume. The same action occurs with the scum but to a lesser degree. Regardless of the efficiency of the operation of the septic tank, a residual of inert solid mate-rial will always remain. Adequate space must be provided in the tank to store this residue during the intervals between cleanings. Sludge and scum will flow out of the tank with the effluent and clog the disposal field in a very short period of time if pumping out of the residue is not performed when required.

Septic tanks are eminently effective in performing their pur-pose when adequately designed, constructed, operated, and maintained. They do not accomplish a high degree of bacte-ria removal. Although the sewage undergoes some treatment in passing through the tank, infectious agents present in the sewage are not removed. The effluent of a septic tank cannot be considered safe. In many respects, the discharged liquid is more objectionable than the influent because it is septic and mal-odorous. This should not be construed in any way as detracting from the value of the tank because its primary purpose is simply to condition the raw sewage so that it will not clog the disposal field.

Continued treatment and the removal of pathogens are accomplished by percolation through the soil. Disease-produc-ing bacteria will die out after a time in the unfavorable environ-ment of the soil. Bacteria are also removed by physical forces during filtration through the soil. This combination of factors achieves the eventual purification of the septic tank effluent.

SeptiC tank loCationThe location of the septic tank should be chosen so as not to cause contamination of any well, spring, or other source of water supply. Underground contamination can travel in any direction for considerable distances unless effectively filtered. Tanks should never be closer than 50 ft to any source of water supply and, where possible, greater distances are preferable. They should be located where the largest possible area will be available for the disposal field and should never be located in swampy areas subject to flooding. Ease of maintenance and accessibility for cleaning are important factors to be considered. When it is anticipated that public sewers will be available in the future, provisions should be made for the eventual connection of the house sewer to such a public source.

tank CapaCityStudies have proven that liberal tank capacity is not only desir-able from a functional viewpoint but is good economical design practice. The liquid capacities recommended in Table 1 make allowances for all household appliances including garbage grinders.

tank materialSeptic tanks must be watertight and constructed of materials not subject to excessive corrosion or decay. Acceptable materi-als are concrete, coated metal, vitrified clay, heavyweight con-crete blocks, or hard-burned bricks. Properly cured precast and cast-in-place, reinforced concrete are believed to be acceptable everywhere. Local codes should be checked as to the acceptabil-ity of the other materials. Steel tanks conforming to U.S. Depart-ment of Commerce Standard 177-62 are generally acceptable. Precast tanks should have a minimum wall thickness of 3 in. and should be adequately reinforced to facilitate handling. When precast slabs are used as covers, they should be watertight, at least 3 in. thick and adequately reinforced. All concrete surfaces should be coated with a bitumastic paint or similar compound to minimize corrosion.

tank aCCeSSAccess should be provided to each compartment of the tank for cleaning and inspection by means of a removable cover or a 20-in. minimum size manhole. When the top of the tank is more than 18 in. below grade, manholes and inspection holes should be extended to approximately 8 in. below grade. They can be extended to grade if a seal is provided to prevent the escape of odors.

tank inletThe invert elevation of the inlet should be at least 3 in. above the liquid level in the tank. This will allow for momentary surges during discharge from the house sewer into the tank and also prevent the backup and stranding of solids in the piping enter-ing the tank.

A vented inlet tee or baffle should be provided to direct the influent downward. The outlet of the tee should terminate at least 6 in. below the liquid level but in no case should it be lower than the bottom of the outlet fitting or device.

tank outletThe outlet fitting or device should penetrate the liquid level just far enough to provide a balance between the sludge and scum storage volumes. This will assure usage of the maximum available tank capacity. A properly operating tank divides itself into three distinct layers: scum at the top, a middle layer free of solids (clear space), and sludge at the bottom layer. While the outlet tee or device retains the scum in the tank, it also limits the amount of sludge that can be retained without passing some of the sludge out with effluent.

Data collected from field observation of sludge accumulations indicate that the outlet device should extend to a distance below the liquid level equal to 40% of the liquid depth. For horizontal cylindrical tanks the percentage should be 35. The outlet device or tee should extend up to within 1 in. of the top of the tank for venting purposes. The space between the top of the tank and

Table 1 Liquid Capacity of Tank (gal)(provides for use of garbage grinders, automatic clothes washers, and other household appliances)

Number of Bedrooms

Recommended Minimum Tank

Capacity

Equivalent Capacity per

Bedroom2 or less 750 375

3 900 3004a 1000 250

a For each additional bedroom, add 250 gal.

MAY/JUNE 2007 Plumbing Systems & Design


the baffle permits gas to pass through the tank into the building sanitary system and eventually to atmosphere where it will not cause a nuisance.

tank ShapeAvailable data indicate that for tanks of a given capacity and depth, the shape of a septic tank is unimportant and that shal-low tanks function equally as well as deep ones. It is recom-mended, however, that the minimum plan dimension be 2 ft and the liquid depth range from 30 to 60 in.

SCum Storage SpaCeSpace is required above the level of the liquid in the tank for the accumulated scum, which floats on top of the liquid. Although there is some variation, approximately 30% of the total amount of scum will accumulate above the liquid level and 70% will be submerged. In addition to the scum storage space, 1 in. should be provided at the top of the tank for free passage of gas through the tank back to the inlet and building drainage system.

For tanks with vertical walls, the distance between the top of the tank and the liquid level should be approximately 20% of the liquid depth. For horizontal cylindrical tanks, the liquid depth should be 79% of the diameter of the tank. This will provide an open area at the top of the tank equal to 15% of the total cross-sectional area of the tank.

CompartmentSAlthough a number of arrangements are possible, compart-ments refer to the number of units in series. They can be sepa-rate units connected together or sections enclosed in one con-tinuous shell with watertight partitions separating the individual compartments.

A single-compartment tank gives acceptable performance, but available research data indicate that a two-compartment tank with the first compartment equal to ½ to 2∕3 of the total volume provides better suspended solids removal. Tanks with three or more equal compartments perform about on an equal basis with a single-compartment tank of the same total capacity. The use of a more than two-compart-ment tank is therefore not recommended. All the requirements of construction stated previously for a single-compartment tank apply to the two-com-partment tank. Each compartment should be pro-vided with an access manhole and venting between compartments for the free passage of gas.

Figure 1 illustrates all the salient features of a typical two-compartment septic tank.

Cleaning of tankSBefore too much sludge or scum is allowed to accu-mulate, septic tanks should be cleaned to prevent the passage of sludge or scum into the disposal field. Tanks should be inspected at least once a year and cleaned when necessary.

Cleaning is usually accomplished by pumping the contents of the tank into a tank truck. A small residual of sludge should be left in the tank for “seeding” purposes. Tanks should never be washed or disinfected after cleaning.

ChemiCal additiveSThe operation of a septic tank is not improved in any way whatsoever by the addition of chemicals;

and such additions are not recommended. Some products that claim to “clean” septic tanks contain sodium hydroxide or potassium hydroxide as the active agent. Such compounds may result in sludge bulking and a sharp increase in alkalinity, which may interfere with digestion. The effluent may severely damage the soil structure of the disposal field and cause accelerated clogging even though some immediate temporary relief may be experienced shortly after application of the product.

On the other hand, ordinary household chemicals in general use around the home will not have a harmful effect on the oper-ation of a septic tank. Small amounts of chorine bleach or small quantities of lye or caustic are not objectionable. If tanks are sized as recommended herein, the dilution of the lye or caus-tics in the tank will be enough to minimize any harmful effects. Soaps, detergents, bleaches, drain cleaners, etc., will have no appreciable adverse effect on the system. However, since both the soil and the organisms might be susceptible to large doses of chemicals, moderation is recommended.

Toilet paper substitutes, paper towels, newspaper, wrapping paper, rags, and sticks should not be introduced into the septic tank. They may not decompose and are likely to lead to clogging of the disposal field.

Backwash from a household water-softening unit has no adverse effect on the operation of a septic tank, but may cause a slight shortening of life of the disposal field installed in a struc-tured clay type soil.

SeptiC tankS for nonreSidential BuildingSTable 1 gives the liquid capacity of tanks on the basis of the number of bedrooms. When designing a septic tank for other types of buildings, Table 2 may be used to estimate the quantity of sewage flow. The quantities listed are merely the best aver-ages presently available and should be modified in localities or establishments where available information indicates a need to do so.

Figure 1 Precast Septic Tank


CONTINUING EDUCATION: Private Sewage Disposal Systems


The retention period of the sewage in a septic tank should be 24 hr. Table 2 gives the gallons per person per day (24 hr). The required liquid capacity of the tank can then be determined by multiplying the values given in the table by the estimated popu-lation.

Tables 3 and 4 give daily gallonages in terms of fixtures for country clubs and public parks, respectively.

SuBSurfaCe Soil aBSorption SyStem

Criteria for deSign The first step in the design of a subsurface soil absorption sewage disposal system is to determine whether the soil is suit-able for the absorption of the septic tank effluent. If it is, the next step is to determine the area required for the disposal field. The soil must have an acceptable percolation rate and should have adequate clearance from ground water. In general, two criteria must be met:

1. The percolation rate should be within the range shown in Table 5 or Table 6.

2. The maximum elevation of the groundwater table should be at least 4 ft below the bottom of the trench or seepage pit. Rock formation or other impervious strata should be at a depth of more than 4 ft below the bottom of the trench or seepage pit.

Table 2 Quantities of Sewage Flows

Type of EstablishmentGallons Per Person Per Day (unless otherwise noted)

Airports (per passenger) 5Apartments—multiple family (per resident) 60Bathhouses and swimming pools 10Camps: Campground with central comfort stations 35 With flush toilets, no showers 25 Construction camps (semi-permanent) 50 Day camps (no meals served) 15 Resort camps (night and day) with limited plumbing 50 Luxury camps 100Cottages and small dwellings with seasonal occupancy 50Country clubs (per resident member) 100Country clubs (per non-resident member present) 25 Dwellings: Boarding houses 50 additional for non-resident boarders 10 Luxury residences and estates 150 Multiple-family dwellings (apartments) 60 Rooming houses 40 Single-family dwellings 75Factories (gallons/person/shift, exclusive of industrial wastes) 35Hospitals (per bed space) 250Hotels with private baths (2 persons per room) 60Hotels without private baths 50Institutions other than hospitals (per bed space) 125Laundries, self service (gal/wash, i.e., per customer) 50Mobile home parks (per space) 250Motels with bath, toilet, and kitchen wastes (per bed space) 50 Motels (per bed space) 40Picnic parks (toilet wastes only) (per picknicker) 5Picnic parks with bathrooms, showers, and flush toilets 10Restaurants (toilet and kitchen wastes per patron) 10Restaurants (kitchen wastes per meal served) 3Restaurants, additional for bars and cocktail lounges 2Schools: Boarding 100 Day, without gyms, cafeterias, or showers 15 Day, with gyms, cafeterias, and showers 25 Day, with cafeterias, but without gyms or showers 20Service stations (per vehicle served) 10Swimming pools and bathhouses 10Theaters: Movie (per auditorium seat) 5 Drive-in (per car space) 5Travel trailer parks Without individual water and sewer hookups (per space) 50 With individual water and sewer hookups (per space) 100Workers: Construction (at semi-permanent camps) 50 Day, at schools and offices (per shift) 15

Table 3 Sewage Flow from Country Clubs

Type of FixtureGallons per Day

per FixtureShowers 500Baths 300Lavatories 100Toilets 150Urinals 100Sinks 50

Table 4 Sewage Flow at Public Parks (during hours when park is open)

Type of FixtureGallons per Day

per FixtureFlush toilets 36Urinals 10Showers 100Faucets 15

Table 6 Allowable Rate of Sewage Application to a Soil Absorption System

Percolation Rate (time for water to fall

1 in.), in minutes

Maximum Rate of Sewage Application (gal/ft2/day)a for Absorption Trenchesb,

Seepage Beds, and Seepage Pitsc

1 or less 5.02 3.53 2.94 2.55 2.2

10 1.615 1.330d 0.945d 0.8

60d, e 0.6a Not including effluents from septic tanks that receive wastes from garbage grinders

and automatic washing machines.b Absorption area is figured as trench bottom area, and includes a statistical allowance

for vertical sidewall area.c Absorption area for seepage pits is effective sidewall area.d Over 30 unsuitable for seepage pits.e Over 60 unsuitable for absorption systems.

Table 5 Absorption Area Requirements for Individual Residencesa

(provides for garbage grinder and automatic clothes washing machines)

Percolation Rate (time required for water to fall 1 in.), in minutes

Required Absorption Area, in ft2/bedroomb, standard trenchc,

seepage bedsc, and seepage pitsd 1 or less 70

2 853 1004 1155 125

10 16515 190

30c, e 25045c, e 300

60c, e, f 330a It is desirable to provide sufficient land area for an entire new absorption system if

needed in the future.b In every case, sufficient land area should be provided for the number of bedrooms

(minimum of two) that can be reasonably anticipated, including the unfinished space available for conversion as additional bedrooms.

c Absorption area is figured as trench bottom area and includes a statistical allowance for vertical side wall area.

d Absorption area for seepage pits is figured as effective side wall area beneath the inlet.e Unsuitable for seepage pits if over 30.f Unsuitable for absorption systems if over 60



If these two primary conditions cannot be met, the site is unsuitable for a soil absorption system and some other seepage disposal system must be employed.

perColation teStSPercolation tests help to determine the acceptability of the site and establish the size of the disposal system. The length of time required for percolation tests varies for different types of soil. The safest method is to make tests in holes that have been kept filled with water for at least 4 hrs and preferably overnight. Percolation rates should be determined on the basis of test data obtained after the soil has had the opportunity to become wetted or saturated.

Enough tests should be made in separate holes to assure the validity of results. The percolation test as developed at the Robert A. Taft Sanitary Engineering Center has proven to be one of the best in the country and is given here in its entirety:

Procedure for Percolation Tests1. Number and Location of Tests. Six or more tests shall be

made in separate test holes spaced uniformly over the pro-posed absorption field site.

2. Type of Test Hole. Dig or bore a hole, with horizontal dimensions of from 4 to 12 in. and vertical sides to the depth of the proposed absorption trench. In order to save time, labor, and volume of water required per test, the holes can be bored with a 4-in. auger.

3. Preparation of a Test Hole. Carefully scratch the bottom and sides of the hole with a knife blade or sharp-pointed instrument, in order to remove any smeared soil surfaces and to provide a natural soil interface into which water may percolate. Remove all loose material from the hole. Add 2 in. of coarse sand or fine gravel to protect the bottom from scouring and sediment.

4. Saturation and Swelling of the Soil. It is important to distinguish between saturation and swelling. Saturation means that the void spaces between soil particles are full of water. This can be accomplished in a short period of time. Swelling is caused by intrusion of water into the individual soil particle. This is a slow process, especially in clay-type soil, and is the reason for requiring a prolonged soaking period. In the conduct of the test, carefully fill the hole with clear water to a minimum depth of 12 in. over the gravel. In most soils, it is necessary to refill the hole by supplying a surplus reservoir of water, possibly by means of an auto-matic syphon, to keep water in the hole for at least 4 hrs and preferably overnight. Determine the percolation rate 24 hrs after water is first added to the hole. This procedure is to ensure that the soil is given ample opportunity to swell and to approach the condition it will be in during the wettest season of the year. Thus, the test will give com-parable results in the same soil, whether made in a dry or wet season. In sandy soils, containing little or no clay, the swelling is not essential, and the test may be made as described under item 5C, after the water from one filling of the hole has completely seeped away.

5. Percolation Rate Measurement. With the exception of sandy soils, percolation rate measurements shall be made on the day following the procedure described under item 4, above.

A. If water remains in the test hole after the overnight swelling period, adjust the depth to approximately 6 in. over the gravel. From a fixed reference point, mea-sure the drop in water level over a 30-min. period. This drop is used to calculate the percolation rate.

B. If no water remains in the hole after the overnight swelling period, add clear water to bring the depth of water in the hole to approximately 6 in. over the gravel. From a fixed reference point, measure the drop in water level at approximately 30-min intervals for 4 hrs, refilling 6 in. over the gravel as necessary. The drop that occurs during the final 30-min period is used to calculate the percolation rate. The drops during prior periods provide information for possible modification of the procedure to suit local circumstances.

C. In sandy soils (or other soils in which the first 6 in. of water seeps away in less than 30 min, after the over-night swelling period), the time interval between mea-surements shall be taken as 10 min and the test run for 1 hr. The drop that occurs during the final 10 min is used to calculate the percolation rate.

aBSorption areaFor locations where the percolation rates and soil characteris-tics prove to be satisfactory, the next step is to determine the required absorption area from Table 5 for residences or from Table 6 for other types of buildings. As noted in the tables, soil in which the percolation rate is slower than 1 in. in 30 min is not suitable for seepage pits and a rate slower than 1 in. in 60 min is not satisfactory for any type of soil absorption system.

There are three types of soil absorption systems:1. Absorption trenches2. Seepage beds3. Seepage pits.

The selection of the system will be affected by the location

of the system in the area under consideration. A safe distance must be maintained between the site and the source of any water supply. No specific distance can be absolutely safe in all localities because of the many variables involved in the under-ground travel of pollution. Table 7 can be used as a guide for establishing minimum distances between various components of a sewage disposal system.

Seepage pits should never be installed in areas of shallow wells or where there are limestone formations and sinkholes

Table 7 Minimum Distance Between Components of Sewage Disposal SystemHorizontal Distance (ft)

Component of System

Well or Suction Line

Water Supply Line (pressure)

Stream Dwelling Property Line

Building sewer 50 10a 50 — —Septic tank 50 10 50 5 10Disposal field and seepage bed

100 25 50 20 5

Seepage pit 100 50 50 20 10Cesspoolb 100 50 50 20 15

a Where the water supply line must cross the sewer line, the bottom of the water service within 10 ft of the point of crossing shall be at least 12 in. above the top of the sewer line. The sewer line shall be of cast iron with leaded or mechanical joints at least 10 ft on either side of the crossing.

b Not recommended as a substitute for a septic tank. To be used only when found necessary and approved by the health authority.




with connection to underground channels through which pollution could travel to water sources.

aBSorption trenCheSThe drain pipe for a soil absorption field may be 12-in. lengths of 4-in. agricultural drain tile, 2–3 ft lengths of open-joint vitrified clay sewer pipe, or perforated non-metallic pipe. Individual laterals should not exceed 100 ft in length and the trench bottom and piping should be level. Use of more and shorter laterals is recommended because if a breakdown should occur in any one lateral, most of the field would still be operative. The space between laterals should be at least twice the depth of gravel to prevent overtaxing the percolative capacity of the adjacent soil.

The depth of the absorption trenches should be at least 24 in. to provide the minimum required gravel depth and earth cover. Additional depth may be required for ground contour adjustment, for extra aggregate speci-fied under the pipe, or for other design purposes. The minimum distance of 4 ft between the bottom of the trench and the water table is essential to minimize groundwater contamination. Freezing is an extremely rare occurrence in a well-constructed system that is kept in continuous operation. It is of course extremely important that the pipe be completely surrounded by the gravel to provide for free movement of the waste water.

The required absorption area is based upon the results of the percolation tests and may be selected from Table 5 or 6.

Example 1For a three-bedroom house and a percolation rate of 1 in. in

15 min, the necessary absorption area will be 3 bedrooms × 190 ft2 per bedroom (Table 5) = 570 ft2. For 2-ft-wide trenches with 6 in. of gravel below the drain pipe the total length of trench will be: 570 ÷ 2 = 285 ft. If this length is divided into three portions (3 laterals), the length of each lateral will be 285 ÷ 3 = 95 ft. If this length is too long for the site, the number of laterals must be increased. Using 5 laterals, the length of each lateral will be 57 ft. If the trenches are separated by 6 ft, the width of the field will be 2-ft-wide trenches × 5 trenches = 10 ft plus 6 ft between trenches × 4 spaces = 24 ft. The total field will then be 57 ft in length by 34 ft. in width for a total area of 1938 ft2 plus the addi-tional land required to keep the field an acceptable distance from property lines, wells, etc.

ConstructionCareful construction is extremely important in achieving a sat-isfactory soil absorption system. Care must be exercised so as not to seal the surfaces on the bottom and sides of the trenches. Trenches should not be excavated when the soil is wet enough to smear or compact easily. Open trenches should always be protected from surface runoff to prevent entrance of silt and debris. All smeared or compacted surfaces should be raked to a depth of 1 in. and loose material removed before placing gravel in the trench.

The pipe should be completely surrounded by clean, graded gravel ranging in size from ½ to 2½ in. Cinders, broken shells, or similar materials are unsuitable as they are too fine and will lead to premature clogging of the soil. The gravel should extend at least 2 in. above the top of the pipe, at least 6 in. below the bottom of the pipe and fill the entire width of the trench. The top

of the gravel should be covered with untreated building paper or a 2-in. layer of hay, straw, or similar pervious material to pre-vent the earth backfill from clogging the gravel. If an impervious covering is used, it will interfere with evapotranspiration at the surface. This is an important factor in the operation of a disposal field and, although evapotranspiration is not generally taken advantage of in the calculations, it provides an added factor of safety.

If tile pipe is used, the upper half of the joint openings should be covered. Drain tile connectors, collars, clips or other spacers with covers for the upper half of the joints may be used to assure uniform spacing, proper alignment, and protection of the joints. They are available in galvanized iron, copper, and plastic.

The problem of root penetration can be avoided by the use of a liberal quantity of gravel around the pipe. There should be at least 12 in. of gravel beneath the pipe when a trench is within 10 ft of large trees or dense shrubbery.

Backfilling of the trench should be hand tamped and the trench should be overfilled at least 4 to 6 in. This will prevent settlement to a point lower than the surface of the adjacent ground where storm water could collect and cause premature saturation of the absorption field and possible complete washout of the trench. Machine tamping or hydraulic backfilling should never be per-mitted. Figure 2 illustrates a typical absorption trench.

Seepage BedSThe use of seepage beds in lieu of standard trenches has been around for over twenty-five years. Common design practice for soil absorption fields is for trenches with widths varying from 12 to 36 in. When trenches are wider than 3 ft they are called seep-age beds. Typically rectangular in shape, seepage beds are com-pact and used when less land is available for system design. Dry climates prove to be a better environment for use than climates having wet, humid conditions. Keep in mind, seepage beds do not have the sidewall area to provide oxygen to the center of a bed and long-term performance depends on the condition of the sidewall area. Slopes greater than 5% are not suitable for this absorption system application. Care must be taken during con-

Figure 2 Section through Typical Absorption Trench



struction so as not to destroy soil structure by compacting the soil in the bottom of the bed. Additionally, the Federal Build-ing Administration has sponsored studies indicating that seep-age beds are a satisfactory method for disposing of the effluent from septic tanks in soils that are satisfactory for soil absorp-tion systems. The studies have demonstrated that the empirical relationship between percolation tests and the bottom area of trenches is applicable for the design of seepage beds.

The three main elements of a seepage bed are the same as those of trenches:1. The absorption surface2. The gravel layer3. The distribution system.

The advantages of seepage beds are (1) a wide bed makes more efficient use of land than a series of long narrow trenches with wasted land between the trenches and (2) efficient use can be made of a variety of modern earth-moving equipment already at the site, which will result in lower costs for the system.

Design Criteria for Seepage BedsThe following criteria should be adhered to in the design of seepage beds:1. The amount of bottom absorption area

shall be the same as for trenches, shown in Table 5 or 6.

2. Percolation tests should be performed as previously outlined.

3. The bed should have a minimum depth of 24 in. to provide a minimum earth backfill cover of 12 in.

4. The bed should have a minimum of 12 in. depth of gravel extending at least 2 in. above and 6 in. below the pipe.

5. The bottom of the bed and the distribu-tion tile or perforated pipe should be level.

6. The drain lines for distributing the efflu-ent from the septic tank should be spaced no greater than 6 ft apart and no greater than 3 ft from the bed sidewalls.

Distribution BoxesAlthough many codes specifically require the use of a distribu-tion box in a soil absorption system, research and field tests have conclusively demonstrated that they offer practically no advantages and can be a source of serious problems in many installations. As a result of its study of distribution boxes, the Public Health Service set forth the following conclusions in the report to the Federal Housing Administration:1. Distribution boxes can be eliminated from septic tank-

soil absorption systems in favor of some other method of distribution without inducing increased failure of disposal fields. In fact, evidence indicates that distribution boxes as presently used may be harmful to the system.

2. Data indicate that on level ground, equal distribution is not necessary if the system is designed so that an overload trench can drain back to the other trenches before failure occurs.

3. On sloping ground a method of distribution is needed to prevent excessive buildup of head and failure of any one trench before the capacity of the entire system is utilized. It is doubtful that distribution boxes as presently used give

equal distribution. Rather, they probably act as diversion devices sending most of the liquid to part of the system.

Because of the above findings, it is recommended that distri-bution boxes be eliminated in all disposal field systems where they are not specifically required by local codes.

Seepage pitSWhere absorption fields are impractical, seepage pits may be applicable. The capacity of a seepage pit should be computed on the basis of percolation tests made in each vertical stratum penetrated. The weighted average of the results should be used to obtain the design figure. Soil strata in which percolation rates are in excess of 30 min/in. should not be included in computing the absorption area.

Effective Area of Seepage PitThe effective area of a seepage pit is the vertical wall area of the pervious ground below the inlet. The area of the bottom of the pit is not considered in calculating the effective area nor is any impervious vertical areas. Table 8 is a compilation of vertical surface area for various pit diameters and depths. The bottom of the pit must always be at least 4 ft above groundwater table.

When more than one pit is required to obtain the necessary absorption area, the distance between the walls of adjacent pits should be equal to three times the diameter of the largest pit. For pits 20 ft or greater in depth the minimum spacing between walls should be 20 ft.

Construction of Seepage PitAll loose material should be removed from the excavated

pit. The pit should be backfilled with clean gravel to a depth of 1 ft above the pit bottom to provide a sound foundation for the pit lining. Material for the lining may be clay or concrete brick, block, or rings. Rings should have weepholes or notches to provide for seepage. Brick and block should be laid dry with staggered joints. Brick should be laid flat to form a 4-in. wall. The outside diameter of the lining should be 12 in. less than the diameter of the pit to provide a 6-in. annular space between the lining and pit wall. This annular space should be filled with clean, coarse gravel to the top of the lining.

Flat concrete covers are recommended. They should be sup-ported by undisturbed earth and extend at least 12 in. beyond the excavation. The cover should not bear on the lining for sup-port. A 9-in. capped opening in the pit cover is convenient for pit inspection. All concrete surfaces should be coated with a bitu-mastic paint or similar product to minimize corrosion.

Table 8 Vertical Wall Areas of Seepage Effective Strata Depth Below Flow Line (below inlet)Diameter of seep-

age pit (feet) 1 foot 2 feet 3 feet 4 feet 5 feet 6 feet 7 feet 8 feet 9 feet 10 feet3 9.4 19 28 38 47 57 66 75 85 944 12.6 26 38 50 63 75 88 101 113 1265 15.7 31 47 63 79 94 110 126 141 1576 18.8 38 57 75 94 113 132 151 170 1887 22.0 44 66 88 110 132 154 176 198 2208 25.1 50 75 101 126 151 176 201 226 2519 28.3 57 85 113 141 170 198 226 251 283

10 31.4 63 94 126 157 188 220 251 283 31411 34.6 69 101 138 173 207 212 276 311 34612 37.7 75 113 151 188 226 264 302 339 377

Example: A pit of 5-foot diameter and 6-foot depth below the inlet has an effective area of 94 square feet. A pit of 5-foot diameter and 16-foot depth has an area of 94 + 157, or 251 square feet.




All connecting piping should be laid on a firm bed of undis-turbed soil throughout their length and at a minimum grade of 2% (¼ in./ft). The pit inlet pipe should extend at least 1 ft into the pit with a tee or ell to direct the flow downward to prevent washing and eroding of the sidewalls. When more than one pit is utilized they should be connected in series.




About This Issue’s ArticleThe May/June 2007 continuing education article is “Private

Sewage Disposal Systems,” Chapter 13 of Engineered Plumbing Design II by A. Cal Laws, PE, CPD.

With the ever-increasing cost of land located in proximity to urban centers, more and more construction is being imple-mented in outlying areas. Sanitary sewers are not usually avail-able in these remote locations and it becomes necessary for the plumbing engineer to design private sewage systems to handle the wastes from buildings. Where the concentration of popula-tion is not sufficient to economically justify the installation of public sewer systems, installation of a septic tank in conjunction with a subsurface soil absorption field has proven to be an excep-tionally satisfactory method of sewage disposal. This chapter explains the different types of private sewage disposal systems for residential and commercial applications as well as criteria for their design and construction.


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CE Questions—“Private Sewage Disposal Systems” (PSD 139)

1. The retention period of sewage in a septic tank should be _________.a. 12 hours, b. 24 hours, c. 36 hours, d. 48 hours

. The first step in the design of a subsurface soil absorption sewage disposal system is _________.a. ascertain the code requirementsb. determine the area required for the disposal fieldc. determine whether the soil is suitable for the

absorption of the septic effluentd. calculate the fixture unit load to be served

. The recommended septic tank capacity for a five-bedroom home is _________.a. 750, b. 900, c. 1,000, d. 1,250

. The minimum distance between a cesspool and a water supply line, as noted in Table , is _________.a. 100 feetb. 20 feetc. 15 feetd. not recommended as a substitute for a septic tank

. What approximate percentage of new home construction employs a septic tank/soil absorption sewage disposal system?a. 15 percentb. 20 percentc. 25 percentd. 30 percent

. Distribution boxes _________.a. are required by many codesb. should be used only when specifically required by codec. offer practically no advantagesd. all of the above

. The absorption area to be provided for an individual residence containing three bedrooms with a percolation rate of three minutes is recommended to be _________.a. 100 square feetb. 200 square feetc. 300 square feetd. 600 square feet

. A covered pit with an open-jointed or perforated lining into which raw sewage is discharged is called a ________.a. septic tankb. cesspoolc. seepage pitd. none of the above

. The drain lines for distributing the effluent from the septic tank should be spaced no grater than _________ apart.a. 3 feet, b. 6 feet, c. 9 feet, d. a and b

10. The quantity of sewage flow from a single-family dwelling per person is _________ gallons per day.a. 50b. 75c. 100d. 125

11. The primary purpose of a septic tank is to _________.a. distribute raw sewage to the leaching fieldb. chemically treat raw sewagec. vent odors to atmosphered. act as a settling tank

1. Sewage pit connecting piping _________.a. should be laid at a minimum grade of 2 percentb. must be 6 inches in diameter minimumc. must be a least 5 feet deepd. none of the above





10 Plumbing Systems & Design MAY/JUNE 2007 PSDMAGAZINE.ORG




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PS&D Continuing Education Answer SheetPrivate Sewage Disposal Systems (PSD 139)


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MAY/JUNE 2007 Plumbing Systems & Design 11


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Sanitary Drainage Systems


NOVEMBER 2007

PSDMAGAZINE.ORG


INTRODUCTIONThe purpose of the sanitary drainage system is to remove efflu-ent discharged from plumbing fixtures and other equipment to an approved point of disposal. A sanitary drainage system gen-erally consists of horizontal branches, vertical stacks, a building drain inside the building, and a building sewer from the build-ing wall to the point of disposal.

To economically design a sanitary drainage system, use the smallest pipes according to the code that can rapidly carry away the soiled water from individual fixtures without clogging the pipes, leaving solids in the piping, generating excessive pneu-matic pressures at points where the fixture drains connect to the stack (which might cause the reduction of trap water seals and force sewer gases back through inhabitable areas), and creating undue noise.

Since vents and venting systems are described in Chapter 3 of this volume, the following discussion centers only on the design of drain and waste systems.

CODES AND STANDARDSPlumbing codes establish a minimum acceptable standard for the design and installation of systems, including sanitary drain-age. There are various model codes, but some states and large cities have adopted plumbing codes other than the ones usually associated with the region. Because of this non-standardization, the actual plumbing code used for each specific project must be obtained from a responsible code official. There are a variety of different codes used to lay out and size interior sanitary drain-age system. Some codes have been adopted by major cities such as New York, Chicago, Los Angles, and others.

The information pertaining to sanitary design for any specific project appears in the approved local plumbing code and must be the primary method used for the accepted methods and sizing. The tables and charts appearing in this chapter are used only to illustrate and augment discussions of sizing methods, sizing procedures, and design methods and should not be used for actual design purposes.

FLOW IN STACKS, BUILDING DRAINS, AND FIXTURE DRAINS

FLOW IN STACKSA stack is considered a main vertical pipe that carries away dis-charge from within a facility of water closets and urinals (soil stack) or other clear water waste from equipment and non-sanitary fixtures (waste stack). Flow in the drain empties into the vertical stack fitting, which may be a long-turn tee-wye or a short-turn or sanitary tee. Each of these fittings permits flow from the drain to enter the stack with a component directed vertically downward. Depending on the rate of flow out of the drain into the stack, the diameter of the stack, the type of stack fitting, and the flow down the stack from higher levels, if any, the discharge from the fixture drain may or may not fill the cross section of the stack at the level of entry. In any event, as soon as

the water enters the stack, the force of gravity rapidly accelerates it downward, and before it falls very far, it assumes the form of a sheet around the wall of the stack, leaving the center of the pipe open for the flow of air.

This sheet of water continues to accelerate until the frictional force exerted by the wall of the stack on the falling sheet of water equals the force of gravity. From that point on—if the distance the water falls is great enough and provided that no flow enters the stack at lower levels to interfere with the sheet—the sheet remains unchanged in thickness and velocity until it reaches the bottom of the stack. The ultimate vertical velocity the sheet attains is called the “terminal velocity.” The distance the sheet must fall to attain this terminal velocity is called the “terminal length.” Following are the formulae developed for calculating the terminal velocity and terminal length:

Equation 1

VT = 3.0(Q)2/5

dLT = 0.052VT

2

where VT = Terminal velocity in stack, fps (m/s) LT = Terminal length below point of flow entry, ft (m) Q = Quantity rate of flow, gpm (L/s) d = Diameter of stack, in. (mm)

Terminal velocity is approximately 10 to 15 fps (3.05 to 4.57 m/s), and this velocity is attained within 10 to 15 ft (3.05 to 4.57 m) of fall from the point of entry.

At the center of the stack is a core of air that is dragged along with the water by friction and for which a supply source must be provided if excessive pressures in the stack are to be avoided. The usual means of supplying this air are through the stack vent or vent stack. The entrained air in the stack causes a pressure reduction inside the stack, which is caused by the frictional effect of the falling sheet of water dragging the core of air along with it.

If the sheet of water falling down the stack passes a stack fit-ting through which the discharge from a fixture is entering the stack, the water from the branch mixes with or deflects the rapidly moving sheet of water. An excess pressure in the drain from which the water is entering the stack is required to deflect the sheet of water flowing downward or mix the branch water with it. The result is a backpressure created in the branch, which increases with the flow rate and flow velocity down the stack and with the rate of flow out of the drain.

The importance of this research is that it conclusively abol-ishes the myth that water falling from a great height will destroy the fittings at the base of a stack. The velocity at the base of a 100-story stack is only slightly and insignificantly greater than the velocity at the base of a three-story stack. The concern is the weight of the stack, which must be supported by clamps at each floor level.

Sanitary Drainage Systems

Reprinted from Plumbing Engineering Design Handbook, Volume 2: Plumbing Systems, Chapter 1: “Sanitary Drainage Systems.” © American Society of Plumbing Engineers.

2 Plumbing Systems & Design NOVEMBER 2007 PSDMAGAZINE.ORG



FLOW IN BUILDING DRAINSWhen the sheet of water reaches the bend at the base of the stack, it turns at approximately right angles into the building drain. Flow enters the horizontal drain at a relatively high veloc-ity compared to the velocity of flow in a horizontal drain under uniform flow conditions. The slope of the building drain is not adequate to maintain the velocity that existed in the vertical sheet when it reached the base of the stack and must flow hori-zontally. The velocity of the water flowing along the building drain and sewer decreases slowly then increases suddenly as the depth of flow increases and completely fills the cross section of the drain. This phenomenon is called a “hydraulic jump.”

The critical distance at which the hydraulic jump may occur varies from immediately at the stack fitting to 10 times the diam-eter of the stack downstream. Less hydraulic jump occurs if the horizontal drain is larger than the stack. After the hydraulic jump occurs and water fills the drain, the pipe tends to flow full until the friction resistance of the pipe retards the flow to that of uniform flow conditions.

FLOW IN FIXTURE DRAINSDetermination of the required drain size is a relatively simple matter, since the fixture drain must be adequate only to carry the discharge from the fixture to which it is attached. Because of the problem of self-siphonage, however, it is advisable to select the diameter of the drain so that the drain flows little more than half full under the maximum discharge conditions likely to be imposed by the fixture.For example, a lavatory drain capable of carrying the flow dis-charged from a lavatory may still flow full over part or all of its length. There are several reasons for this. The vertical compo-nent of the flow out of the trap into the drain tends to make the water attach itself to the upper elements of the drain, and a slug of water is formed, filling the drain at that point. If there is not sufficient air aspirated through the overflow, the pipe will flow full for part of its length, with the average velocity of flow being less than the normal velocity for the rate of flow in the drain at a given slope.

If the fixture considered is a water closet, the surge of water from the closet will continue almost without change even along a very long drain until it reaches the stack. Thus, it can be assumed, for all practical purposes, that the surge caused by the discharge of a water closet through a fixture drain reaches the stack or horizontal branch with practically the same velocity it had when it left the fixture.

PNEUMATIC PRESSURES IN A SANITARY DRAINAGE SYSTEMBecause of the pressure conditions in a stack and a building drain, the wastewater does not fill the cross section anywhere, so the air can flow freely along with the water. The water flowing down the wall of the stack drags air with it by friction and carries it through the building drain to the street sewer. The air is then vented through the main street sewer system so dangerous pressures do not build up. The generally accepted pressure is plus or minus 1 inch of water column.

If air is to enter the top of the stack to replace the air being carried along with the water, there must be a pressure reduction inside the stack. Because of the head loss necessary to accelerate the air and to provide for the energy loss at the entrance, however, this pres-

sure reduction is negligible; it amounts to only a small fraction of an inch (a millimeter) of water. What causes appreciable pres-sure reductions is the partial or complete blocking of the stack by water flowing into the stack from a horizontal branch.

A small increase in pneumatic pressure will occur in the building drain even if there is no complete blocking of the air-flow by a hydraulic jump or by submergence of the outlet and the building sewer. This is due to the decrease in cross-sectional area available for airflow when the water flowing in the drain has adapted itself to the slope and diameter of the drain.

FIXTURE DISCHARGE CHARACTERISTICSThe discharge characteristic curves—flow rates as a function of time—for most water closet bowls have the same general shape, but some show a much lower peak and a longer period of dis-charge. The discharge characteristics for various types of water closet bowls, particularly low-flow water closets, have a sig-nificant impact on estimating the capacity of a sanitary drain-age system. Other plumbing fixtures, such as sinks, lavatories, and bathtubs, may produce similar surging flows in drainage systems, but they do not have as marked of an effect as water closets.

Drainage Loads Single-family dwellings contain certain plumbing fixtures—one or more bathroom groups, each consist-ing of a water closet, a lavatory, and a bathtub or shower stall; a kitchen sink, dishwasher, and washing machine; and, possibly, a set of laundry trays. Large buildings also have other fixtures, such as slop sinks and drinking water coolers. The important characteristic of these fixtures is that they are not used continu-ously. Rather, they are used with irregular frequencies that vary greatly during the day. In addition, the various fixtures have quite different discharge characteristics regarding both the aver-age rate of flow per use and the duration of a single discharge. Consequently, the probability of all the fixtures in the building operating simultaneously is small. Assigning drainage fixture unit (dfu) values to fixtures to represent their load-producing effect on the plumbing system was originally proposed in 1923 by Dr. Roy B. Hunter. The fixture unit values were designed for application in conjunction with the probability of simultaneous use of fixtures to establish the maximum permissible drainage loads expressed in fixture units rather than in gallons per minute (gpm, L/s) of drainage flow. Table 1 gives the recommended fix-ture unit values. The plumbing engineer must conform to local code requirements.

Table 1 Residential Drainage Fixture Unit (dfu) Loads

Fixture Drainage Fixture Units (dfu) IPC UPCBathtub 2 3Clothes washer 3 3Dishwasher 2 2Floor drain 3 * * Trap loadingsLaundry tray 2 2 1¼" 1 dfuLavatory, single 1 1 1½" 3 dfuLavatory, in sets of 2 or 3 2 2 2“ 4 dfuShower (each head) 2 2 3" 6 dfuSink (including dishwasher and garbage disposer) 3 3 4" 8 dfuWater closet (1.6-gpf gravity tank) 4 4Water closet (1.6-gpf flushometer tank) 5 5Water closet (1.6-gpf flushometer valve) 4 4

NOVEMBER 2007 Plumbing Systems & Design 3


A dfu is a quantity of load-producing discharge in relation to that of a lavatory.

Dr. Hunter conceived the idea of assigning a fixture unit value to represent the degree to which a fixture loads a system when used at the maximum assumed flow and frequency. The pur-pose of the fixture unit concept is to make it possible to calcu-late the design load of the system directly when the system is a combination of different kinds of fixtures, each having a unique loading characteristic. Current or recently conducted studies of drainage loads on drainage systems may change these values. These include studies of (1) reduced flow from water-saving fix-tures; (2) models of stack, branch, and house drain flows; and (3) actual fixture use.

STACK CAPACITIESThe criterion of flow capacities in drainage stacks is based on the limitation of the water-occupied cross section to a speci-fied fraction (rs) of the cross section of the stack where terminal velocity exists, as suggested by earlier investigations.

Flow capacity can be expressed in terms of the stack diameter and the water cross section:

Equation 2Q = 27.8 × rs

5/3 × D8/3

where Q = Capacity, gpm (L/s) rs = Ratio of cross-sectional area of the sheet of water to

cross-sectional area of the stack D = Diameter of the stack, in. (mm)

Values of flow rates based on r = ¼, 7⁄24, and 1⁄3 are tabulated in Table 2.

Whether or not Equation 2 can be used safely to predict stack capacities remains to be confirmed and accepted. However, it provides a definite law of variation of stack capacity with diam-eter. If this law can be shown to hold for the lower part of the range of stack diameters, it should be valid for the larger diam-eters. It should be remembered that both F.M. Dawson and Dr. Hunter, in entirely independent investigations, came to the conclusion that slugs of water, with their accompanying violent pressure fluctuations, did not occur until the stack flowed ¼ to 1⁄3 full. Most model codes have based their stack loading tables on a value of r = ¼ or 7⁄24.

The recommended maximum permissible flow in a stack is 7⁄24 of the total cross-sectional area of the stack. By substituting r = 7⁄24 into Equation 2, the corresponding maximum permissible flow for the various sizes of pipe in gpm (L/s) can be determined. Table 1-3 lists the maximum permissible fixture units (fu) to be conveyed by stacks of various sizes. The table was created by taking into account the probability of simultaneous use of fix-

tures. For example, the 500 fu is the maximum loading for a 4-in. (100-mm) stack, thus 147 gpm (9.3 L/s) is equivalent to 500 fu. This is the total load from all branches.

It should be noted that there is a restriction of the amount of flow permitted to enter a stack from any branch when the stack is more than three branch intervals. If an attempt is made to introduce too large a flow into the stack at any one level, the inflow will fill the stack at that level and will even back up the water above the elevation of inflow, which will cause violent pressure fluctuations in the stack—resulting in the siphoning of trap seals—and may also cause sluggish flow in the horizontal branch. This problem was solved in a study of stack capacities made by Wyly and Eaton at the National Bureau of Standards for the Housing and Home Finance Agency in 1950.

The water flowing out of the branch can enter the stack only by mixing with the stream flowing down the stack or by deflecting it. Such a deflection of the high-velocity stream coming down the stack can be accomplished only if there is a large enough hydrostatic pressure in the branch, since a force of some kind is required to deflect the downward flowing stream and therefore change its momentum. This hydrostatic pressure is built up by the backing up of the water in the branch until the head thus created suffices to change the momentum of the stream already in the stack to allow the flow from the branch to enter the stack.

The magnitude of the maximum hydrostatic pressure that should be permitted in the branch as a result of the backing up of the spent water is based on the consideration that this backup should not be sufficiently great to cause the water to back up into a shower stall or to cause sluggish flow. It is half the diam-eter of the horizontal branch at its connection to the stack. That is, it is the head measured at the axis of the pipe that will cause the branch to flow full near the exit.

When a long-turn tee-wye is used to connect the branch to the stack, the water has a greater vertical velocity when it enters the stack than it does when a sanitary tee is used, and the back pressures should be smaller in this case for the same flows down the stack and in the branch.

Table 3 shows the maximum permissible fu loads for sanitary stacks. The procedure for sizing a multistory stack (greater than three floors) is to first size the horizontal branches connected to the stack. This is done by totaling the fixture units connected to

Table 3 Horizontal Fixture Branches and Stacks

Diameter of pipe, in.

(mm)

Maximum Number of Drainage Fixture Units (dfu) that May Be Connected

Any Horizontal

Fixture Brancha

1 Stack of 3 or Fewer

Branch Intervals

Stacks with More than 3 Branch Intervals

Total for Stack

Total at 1 Branch Interval

1½ (40) 3 4 8 22 (50) 6 10 24 62½ (65) 12 20 42 93 (80) 20b 48b 72b 20b

4 (100) 160 240 500 905 (125) 360 540 1,100 2006 (150) 620 960 1,900 3508 (200) 1,400 2,200 3,600 600

10 (250) 2,500 3,800 5,600 1,00012 (300) 3,900 6,000 8,400 1,50015 (380) 7,000

a Does not include branches of the building drain.b No more than two water closets or bathroom groups within each branch interval or more than

six water closets or bathroom groups on the stack.

Table 2 Capacities of Stacks

Pipe Size, in. (mm)

Flow, gpm (L/s)r = 1⁄4 r = 7⁄24 r = 1⁄3

2 (50) 17.5 (1.1) 23.0 (1.45) 28 (1.77)3 (80) 52 (3.28) 70 (4.41) 85 (5.36)4 (100) 112 (7.07) 145 (9.14) 180 (11.35)5 (125) 205 (12.93) 261 (16.5) 324 (20.44)6 (150) 330 (20.82) 424 (26.8) 530 (33.43)8 (200) 710 (44.8) 913 (57.6) 1,140 (72)

10 (250) 1,300 (82.0) 1,655 (104.4) 2,068 (130.5)12 (300) 2,082 (131.4) 2,692 (170) 3,365 (212.3)


CONTINUING EDUCATION: Sanitary Drainage Systems


each branch and size in accordance with column 2 in Table 3. Next, total all the fixture units connected to the stack and determine the size from the same table, under column 4. Immediately check the next column, “Total at One Branch Inter-val,” and determine if this maximum is exceeded by any of the branches. If it is exceeded, the size of the stack as originally determined must be increased at least one size, or the loading of the branches must be redesigned so maximum condi-tions are satisfied. Take, for example, a 4-in. (100-mm) stack more than three stories in height. The maximum loading for a 4-in. (100-mm) branch is 160 fu, as shown in column 2 of Table 3. This load is limited by column 5 of the same table, which permits only 90 fu to be introduced into a 4-in. (100-mm) stack in any one-branch interval. The stack would have to be increased in size to accommodate any branch load exceeding 90 fu.

To illustrate clearly the requirements of a stack with an offset of more than 45° from the vertical, Figure 1 shows the sizing of a stack in a 12-story building where there is one offset between the fifth and sixth floors and another offset below the street floor.

Sizing is computed as follows:

Step 1. Compute the fixture units connect-ed to the stack. In this case, assume 1,200 fixture units are connected to the stack from the street floor through the top floor.

Step 2. Size the portion of the stack above the fifth-floor offset. There are 400 fixture units from the top floor down through the sixth floor. According to Table 3, column 4, 400 fixture units require a 4-in. (100-mm) stack.

Step 3. Size the offset on the fifth floor. An offset is sized and sloped like a building drain.

Step 4. Size the lower portion of the stack from the fifth floor down through the street floor. The lower portion of the stack must be large enough to serve all fixture units connected to it, from the top floor down (in this case 1,200 fixture units). According to Table 3, 1,200 fixture units require a 6-in. (150-mm) stack.

Step 5. Size and slope the offset below the street floor the same as a building drain.

The fixture on the sixth floor should be connected to the stack at least 2 ft (0.6 m) above the offset. If this is not possible, then connect them separately to the stack at least 2 ft (0.6 m) below the offset. If this is not possible either, run the fixture drain down to the fifth or fourth floor and connect to the stack at that point.

CAPACITIES OF SLOPING DRAINSThe characteristics of sewage are the same as plain water. Capacities of horizontal or sloping drains are complicated by surging flow.

The determination of drain size is based on highly fluctuating or surging flow conditions in the horizontal branches carrying the discharge of fixtures to the soil or waste stack. After falling down the vertical stack, the water is assumed to enter the build-ing drain with peaks of the surges leveled off somewhat but still in a surging condition.

In a large building covering considerable ground area there are probably several primary branches and certainly at least one secondary branch. After the water enters the building drain, the surge continues to level off, becoming more and more nearly uniform, particularly after the hydraulic jump has occurred. If the secondary branch is long enough, and if the drain serves a large number of fixtures, the flow may become substantially uniform before it reaches the street sewer.

Figure 1 Procedure for Sizing an Offset Stack



STEADY, UNIFORM FLOW CONDITIONS IN SLOPING DRAINSAlthough the equations of steady, uniform flow in sloping drains should not be used to determine the capacities of sloping drains in which surging flow exists, flow computations based on these formulas afford a rough check on values obtained by the more complicated methods that are applicable to surging flow. Hence, three of the commonly used formulas for flow in pipes will be considered: (1) Hazen and Williams, (2) Darcy-Weisbach, and (3) Manning.

Hazen and Williams formula This formula is usually written as follows:

Equation 3V = 1.318 × C × R0.63 × S0.54

where V = Mean velocity of flow, fps (m/s) C = Hazen and Williams coefficient R = Hydraulic radius of pipe, ft (m) S = Slope of pressure gradient

The exponents of R and S in Equation 3 have been selected to make the coefficient C as nearly constant as possible for different pipe diameters and for dif-ferent velocities of flow. Thus, C is approximately constant for a given pipe roughness.

Darcy-Weisbach formula In this formula the dimensionless friction coefficient f varies with the diameter of the pipe, the velocity of flow, the kinematic viscosity of the fluid flowing, and the roughness of the walls. It is usually written as follows:

Equation 4

hf = f L V2

D 2gwhere hf = Pressure drop or friction loss, ft (m) f = Friction coefficient L = Length of pipe, ft (m) D = Diameter of pipe, ft (m) V = Mean velocity of flow, fps (m/s) g = Acceleration of gravity, 32.2 fps2 (9.8 m/s2)

Manning formula The Manning formula, which is similar to the Hazen and Williams formula, is meant for open-channel flow and is usually written as follows:

Equation 5

V = 1.486 × R2/3 × S1/2 = 1.486 × R0.67 × S0.50n n

In this formula, n is the Manning coefficient and varies with the roughness of the pipe and the pipe diameter.

The quantity of flow is equal to the cross-sectional area of flow times the velocity of flow obtained from the above three equa-tions. This can be expressed as:

Equation 5aQ = AV

where Q = Quantity rate of flow, cfs (m3/s) A = Cross-sectional area of flow, ft2 (m2) V = Velocity of flow, fps (m/s)

By substituting the value of V from Manning’s formula, the quantity of flow in variously sized drains of the same material can be calculated as

Equation 5b

Q = A ×( 1.486 ) × R2/3 × S1/2n

This is the formula used by many plumbing engineers to deal with sloping drain problems. The significant hydraulic param-eters used in the above equation are listed in Table 4.

It should be noted that the units in the above equations should be converted to the proper units whenever utilizing Equations 5a or 5b.

SLOPE OF HORIzONTAL DRAINAGE PIPINGHorizontal drains are designated to flow at half-full capacity under uniform flow conditions to minimize the generation of pneumatic pressure fluctuations. A minimum slope of ¼ in./ft (6.4 mm/m) should be provided for pipe 3 in. (80 mm) and smaller, 1⁄8 in./ft (3.2 mm/m) for 4-6-in. (100-150-mm) pipe, and 1⁄16 in./ft (1.6 mm/m) for pipe 8 in. (200 mm) and larger. These slopes are not a hard and fast rule and might be less under unusual conditions. The signer must confirm required slopes with the local code authority. These minimum slopes are required to maintain a velocity of flow greater than 2 fps for scouring action. Table 5 gives the approximate velocities for given flow, slopes, and diameters of horizontal drains based on the Manning formula for half-full pipe and n = 0.015.

A flow velocity of 2 fps will prevent the solids within a pipe from settling out and forming a system stoppage. Table 6 has been prepared to give the size of a pipe in conjunction with flow rate to maintain a self-cleansing velocity of 2 fps.

LOAD OR DRAINAGE PIPINGThe recommended loads for building drains and sewers are tab-ulated in Table 7. This table shows the maximum number of fix-ture units that may be connected to any portion of the building drain or building sewer for given slopes and diameters of pipes. For example, an offset below the lowest branch with 1,300 fu at ¼ in./ft (6.4 mm/m) slope requires an 8-in. (200-mm) pipe.

For devices that provide continuous or semi-continuous flow into the drainage system, such as sump pumps, ejectors, and air-conditioning equipment, a value of 2 fu can be assigned for each gpm (L/s) of flow. For example, a sump pump with a discharge rate of 200 gpm (12.6 L/s) is equivalent to 200 × 2 = 400 fu.

COMPONENTS OF SANITARY DRAINAGE SYSTEMS

SUMPS AND EjECTORSThe distinction between sump and ejector pumps is more termi-nology than actual fact. A sump pump is designed to transport clear, non-sanitary wastewater with some turbidity and sus-

Table 4 Values of R, R2/3, AF, and AH

Pipe Size, in. (mm) R = D⁄4, ft (mm) R2/3, ft (mm)

AF (Cross-Sectional Area for Full Flow),

ft2 (m2)

AH (Cross-Sectional Area for Half-full

Flow), ft2 (m2)1½ (40) 0.0335 (1.02) 0.1040 (3.17) 0.01412 (0.0013) 0.00706 (0.00065)2 (50) 0.0417 (1.27) 0.1200 (3.66) 0.02180 (0.0020) 0.01090 (0.0009)2½ (65) 0.0521 (1.59) 0.1396 (4.24) 0.03408 (0.0031) 0.01704 (0.0015)3 (80) 0.0625 (1.90) 0.1570 (4.78) 0.04910 (0.0046) 0.02455 (0.0023)4 (100) 0.0833 (2.54) 0.1910 (5.82) 0.08730 (0.0081) 0.04365 (0.0040)5 (125) 0.1040 (3.17) 0.2210 (6.74) 0.13640 (0.0127) 0.06820 (0.0063)6 (150) 0.1250 (3.81) 0.2500 (7.62) 0.19640 (0.0182) 0.09820 (0.0091)8 (200) 0.1670 (5.09) 0.3030 (9.23) 0.34920 (0.0324) 0.17460 (0.0162)

10 (250) 0.2080 (6.33) 0.3510 (10.70) 0.54540 (0.0506) 0.27270 (0.0253)12 (300) 0.2500 (7.62) 0.3970 (12.10) 0.78540 (0.0730) 0.39270 (0.0364)15 (380) 0.3125 (9.53) 0.4610 (14.05) 1.22700 (0.0379) 0.61350 (0.0570)




pended solids no larger than sand grains. An ejector pump is designed to transport sanitary waste and larger solids suspended in the effluent. All effluent is a liquid with solids suspended in it but has the same hydraulic characteristics as water.

Building drains that cannot flow directly into a sewer by grav-ity must be discharged into a covered basin from which fluid is lifted into the building’s gravity drainage system by automatic pump equipment or by any equally efficient method approved by the administrative authority.

An ejector basin must be of airtight construction and must be vented. It is airtight to prevent the escape of foul odors gen-erated by sanitary waste from the subdrainage system. Since it is airtight, a vent is required to relieve the air in the basin as wastes discharge into it and also to supply air to the basin while the contents are being discharged to the sanitary gravity drain-age system. A duplex pump system shall be used. If one pump breaks down, the control system will alert the second pump to start. The system will remain in operation and no damage will be caused by the cessation of system operation. When a

Table 5 Approximate Discharge Rates and Velocities in Sloping Drains, n = 0.015a

Actual Inside Diameter of

Pipe, in. (mm)

Actual Inside Half-full Flow Discharge Rate and Velocity1⁄16 in./ft (1.6 mm/m) Slope 1⁄8 in./ft (3.2 mm/m) Slope 1⁄4 in./ft (6.4 mm/m) Slope 1⁄2 in./ft (12.7 mm/m) Slope

Disch., gpm (L/s)

Velocity, fps (mm/s)

Disch., gpm (L/s)


Disch., gpm (L/s)


Disch., gpm (L/s)


1¼ (31.8) 3.40 (0.21) 1.78 (45.5)13⁄8 (34.9) 3.13 (0.20) 1.34 (0.41) 4.44 (0.28) 1.90 (48.3)1½ (38.9) 3.91 (0.247) 1.42 (0.43) 5.53 (0.35) 2.01 (51.1)

15⁄8 (41.28) 4.81 (0.30) 1.50 (0.46) 6.80 (0.38) 2.12 (53.9)2 (50.8) 8.42 (0.53) 1.72 (0.52) 11.9 (0.75) 2.43 (61.8)2½ (63.5) 10.8 (0.68) 1.41 (0.43) 15.3 (0.97) 1.99 (0.61) 21.6 (1.36) 2.82 (71.7)3 (76.3) 17.6 (1.11) 1.59 (0.49) 24.8 (1.56) 2.25 (0.69) 35.1 (2.21) 3.19 (81.1)4 (101.6) 26.70 (1.68) 1.36 (34.6) 37.8 (2.38) 1.93 (0.59) 53.4 (3.37) 2.73 (0.83) 75.5 (4.76) 3.86 (98.2)5 (127) 48.3 (3.05) 1.58 (40.2) 68.3 (4.30) 2.23 (0.68) 96.6 (6.10) 3.16 (0.96) 137 (8.64) 4.47 (113.7)6 (152.4) 78.5 (4.83) 1.78 (45.3) 111 (7.00) 2.52 (0.77) 157 (10) 3.57 (1.09) 222 (14.0) 5.04 (128.2)8 (203.2) 170 (10.73) 2.17 (55.2) 240 (15.14) 3.07 (0.94) 340 (21.5) 4.34 (1.32) 480 (30.3) 6.13 (155.9)

10 (256) 308 (19.43) 2.52 (64.1) 436 (27.50) 3.56 (1.09) 616 (38.9) 5.04 (1.54) 872 (55.0) 7.12 (181.0)12 (304.8) 500 (31.55) 2.83 (72.0) 707 (44.60) 4.01 (1.22) 999 (63.0) 5.67 (1.73) 1413 (89.15) 8.02 (204.0)

a n = Manning coefficient, which varies with the roughness of the pipe.For full flow: Multiply discharge by 2.00.For full flow: Multiply velocity by 1.00.For smoother pipe: Multiply discharge and velocity by 0.015 and divide by n of another pipe.

Table 7 Building Drains and Sewersa

Diameter of Pipe, in.

(mm)

Maximum Permissible Fixture Units for Sanitary Building Drains and Runouts

From StacksSlope, in./ft (mm/m)

1⁄16 (1.6) 1⁄8 (3.2) 1⁄4 (6.4) 1⁄2 (12.7)2 (50) 21 262½ (65) 24 313 (80) 20 42b 50b

4 (100) 180 216 2505 (125) 390 480 5756 (150) 700 840 1,0008 (200) 1400 1600 1,920 2,300

10 (250) 2500 2900 3,500 4,20012 (300) 2900 4600 5,600 6,70015 (380) 7000 8300 10,000 12,000

a On-site sewers that serve more than one building may be sized according to the current standards and specifications of the administrative authority for public sewers.

b No more than two water closets or two bathroom groups, except in single-family dwellings, where no more than three water closets or three bathroom groups may be installed. Check the local codes in the area served for exact requirements or restrictions.

Table 6 Slopes Of Cast Iron Soil Pipe Sanitary Sewers Required To Obtain Self-cleansing Velocities Of 2.0 And 2.5 Ft./sec. (Rased On Mannings Formula With N = .012)

Pipe Size (in.)

Velocity (ft./sec.)

1/4 Full 1/2 Full 3/4 Full FullSlope

(ft./ft.)Flow

(Gal./min.)Slope

(ft./ft.)Flow

(Gal./min.)Slope

(ft./ft.)Flow

(Gal./min.)Slope

(ft./ft.)Flow

(Gal./min.)2.0 2.0 0.0313 4.67 0.0186 9.34 0.0148 14.09 0.0186 18.76

2.5 0.0489 5.04 0.0291 11.67 0.0231 17.62 0.0291 23.453.0 2.0 0.0178 10.71 0.0107 21.46 0.0085 32.23 0,0107 42.91

2.5 0.0278 13.47 0.0167 26.62 0.0133 40.29 0.0167 53.644.0 2.0 0.0122 19.03 0.0073 38.06 0.0058 57.01 0.0073 76.04

2.5 0.0191 23.79 0.0114 47.58 0.0091 71.26 0.0114 95.055.0 2.0 0.0090 29.89 0.0054 59.79 0.0043 89.59 0.0054 119.49

2.5 0.0141 37.37 0.0085 74.74 0.0067 111.99 0.0085 149.366.0 2.0 0.0071 43.18 0.0042 86.36 0.0034 129.54 0.0042 172.72

2.5 0.0111 53.98 0.0066 101.95 0.0053 161.93 0.0066 215.908.0 2.0 0.0048 77.20 0.0029 154.32 0.0023 231.52 0.0029 308.64

2.5 0.0075 96.50 0.0045 192.90 0.0036 289.40 0.0045 385.7910.0 2.0 0.0036 120.92 0.0021 241.85 0.0017 362.77 0.0021 483.69

2.5 0.0056 151.15 0.0033 302.31 0.0026 453.46 0.0033 604.6112.0 2.0 0.0028 174.52 0.0017 349.03 0.0013 523.55 0.0017 678.07

2.5 0.0044 218.15 0.0026 436.29 0.0021 654.44 0.0026 612.5815.0 2.0 0.0021 275.42 0.0012 550.84 0.0010 826.26 0.0012 1101.68

2.5 0.0032 344.28 0.0019 688.55 0.0015 1032.83 0.0019 1377.10



duplex unit is used, each pump should be sized for 100 percent flow, and it is good practice to have the operation of the pumps alternate automatically.

A sump basin need not be airtight or vented because of the lack of objectionable odors. Incoming water is collected in the sump before it is pumped to the gravity drain pipe. Heavy-flow drains require large sumps to retain greater-than-usual amounts of water, thereby creating more head pressure on the pipe inlet. Most manufacturers make their basins with bottom, side, or angle inlets and with inside caulk, no-hub, push-on, spigot, or screwed connections. Outlet connections are made to accept pressure-type pipe joints. No-hub pipe and fittings are not acceptable on pumped discharge piping due to the pressure limitations of the pipe joints.

Sump and ejector systems normally use a wet pit and will have the pumps either above slab or submerged. They are controlled with a float switch or electronic, with control switches mounted inside the basin. Typical ejector installations are illustrated in Figure 2. Typical ejector installations are illustrated in Figure 3.

CLEANOUTSThe cleanout provides access to horizontal and verti-cal lines to facilitate inspection and provide a means of removing obstructions such as solid objects, greasy wastes, and hair. Cleanouts, in general, must be gas- and water-tight, provide quick and easy plug removal, allow ample space for the operation of cleaning tools, have a means of adjustment to finished surfaces, be attractive in appearance, and be designed to support whatever traffic is directed over them.

Some cleanouts are designed with a neoprene seal plug, which prevents “freezing” or binding to the fer-rule. All plugs are machined with a straight or running thread and a flared shoulder for the neoprene gasket, permitting quick and certain removal when necessary. A maximum opening is provided for tool access. Recessed covers are available to accommodate carpet, tile, ter-razzo, and other surfaces finishes and are adjustable to the exact floor level established by the adjustable hous-ing or by the set screws.

Waste lines are normally laid beneath the floor slabs at a distance sufficient to provide adequate backfill over the joints. Cleanouts are then brought up to floor-level grade by pipe extension pieces. Where the sewer line is at some distance below grade and not easily accessible through extensions, small pits or manholes with access covers must be installed. When cleanouts are installed in traffic areas, the traffic load must be considered when the materials of construction are selected.

The size of the cleanout within a building should be the same size as the piping, up to 4 in. (100 mm). For larger size interior piping, 4-in. (100-mm) cleanouts are adequate for their intended purpose; however, 6-in. (150-mm) cleanouts are recommended to allow for a larger variety of access needs such as for sewer video equipment.

Cleanouts should be provided at the following loca-tions:

1. Five ft 0 in. (1.5 m) outside or inside the building at the point of exit.

2. At every change of direction greater than 45°.

3. A maximum distance between cleanouts of 50 ft (15.1 m) should be maintained for piping 4 in. (100 mm) and smaller, and of 75 ft (22.9 m) for larger piping. Underground sanitary sewer piping larger than 10 in. (250 mm) in diameter should be provided with cleanouts at every change of direction and every 150 ft (45.7 m).

4. At the base of all stacks.5. To comply with applicable codes.

Optional locations include:

1. At the roof stack terminal.

2. At the end of horizontal fixture branches or waste lines.3. At fixture traps. (Fixture traps can be pre-manufactured with

cleanout plugs, although some codes prohibit the installa-tion of this kind of trap.)

Figure 2 Typical Ejector Pump Installation




FLOOR DRAINS AND FLOOR SINKSA large-diameter drain with a deep sump connected to a large-diameter pipe passes more water faster than a smaller drain. However, economics do not allow the designer arbitrarily to select the largest available drain when a smaller, less-expen-sive unit will do a satisfactory job. High-capacity drains are

intended for use primarily in locations where the flow reaches high rates, such as malls, wash-down areas, and certain indus-trial applications. Table 8, which shows minimum ratios of open grate area based on pipe diameter, is offered as a guide for the selection of drains where the drain pipe diameter is known.

The only drawback to using the open-area-pipe-diameter-ratio method is that all drain manufacturers do not list the total open areas of grates in their catalogs. This information usually can be obtained upon request, however.

For the sizing of floor drains for most indoor applications, the capacity of a drain is not extremely critical because the drain’s primary function is to handle minor spillage or fixture overflow. The exceptions are, of course, cases where equipment discharges to the drain, where automatic fire sprinklers may deluge an area with large amounts of water, and where flushing of the floor is required for sanitation.

Generally located floor drains or drains installed to anticipate a failure may not receive sufficient water flow to keep the pro-tective water seal or plumbing trap from evaporating. If it does

evaporate, sewer gases will enter the space. Auto-matic or manual trap primers should be installed to maintain a proper trap seal. (A small amount of vegetable oil will dramatically reduce the evapora-tion rate of infrequently used floor drains and floor sinks.)

Figure 4 shows the basic components of a floor drain.

GRATES / STRAINERSThe selection of grates is based on use and the amount of flow. Light-traffic areas may have a nickel-bronze-finished grate, while mechanical areas may have a large, heavy-duty, ductile iron grate.

The wearing of spike-heeled shoes prompted the replacement of grates with a heel-proof, ¼-in.-square (6.4-mm) grate design in public toilet rooms, corri-dors, passageways, promenade decks, patios, stores, theaters, and markets. Though this type of grating has less drainage capacity than the previous one, its safety feature makes it well worth the change.

Grates or strainers should be secured with stain-less-steel screws in nickel-bronze tops. Vandal-proof fasteners are available from most manufacturers. Vandal-proofing floor drain grates is advisable. If there is public access to the roof, consideration must be given to protecting the vent openings from van-dals.

In school gymnasium shower rooms, where the blocking of flat-top shower drains with paper towels can cause flooding, dome grates in the corners of the room or angle grates against the walls can be specified in addition to the regular shower drains. Shower-room gutters and curbs have become unde-sirable because of code requirements and the obvi-ous dangers involved. Therefore, the passageways from shower areas into locker areas need extended-length drains to prevent runoff water from entering the locker areas.

Where grates are not secured and are subject to vehicular traffic, it is recommended that non-tilting and /or tractor-type grates be installed. When a grate

Figure 3 Typical Submerged Sump Pump Installation

Table 8 Recommended Grate Open Areas for Various Floor Drains With Outlet Pipe Sizes

Nominal Pipe Size, in. (mm)

Recommended Minimum Grate Open Area for Floor Drains

Transverse Area of Pipe, in.2a

(× 10 mm2)

Minimum Inside Area, in.2

(× 10 mm2)1½ (40) 2.04 (1.3) 2.04 (1.3)2 (50) 3.14 (2.0) 3.14 (2.0)3 (80) 7.06 (4.6) 7.06 (4.6)4 (100) 12.60 (8.1) 12.06 (8.1)5 (125) 19.60 (12.7) 19.60 (12.7)6 (150) 28.30 (18.3) 28.30 (18.3)8 (200) 50.25 (32.4) 50.24 (32.4)

a Based on extra-heavy soil pipe, nominal internal diameter.



starts to follow a wheel or is hit on one edge and starts to tilt, the skirt catches the side of the drain body and the grate slides back into its original position. Ramp-drain gratings should be slightly convex because rapidly flowing ramp water has a ten-dency to flow across the grate. A better solution to this problem is to place flat-top grates on a level surface at the bottom of the ramp, rather than on the ramp slope.

A technique in casting grates is the reversal of pattern draft, which removes the razor-sharp edges created when grates are buffed. See Figure 5. The prevalent buffing technique is called scuff-buff because it gives the grate a slightly used appearance. The use of slots in grates is becoming obsolete because of the slicing edges they create, which cause excess wear and tear on the wheels of hand-trucks and other vehicles. Square openings are more desirable because they shorten this edge and provide greater drainage capacity than round holes.

FLASHING RINGThis component makes an effective seal, which prevents water from passing around the drain to the area below.

SEDIMENT BUCKETA sediment bucket is an additional internal strainer designed to collect debris that gets by the regular strainer. It is required wherever the drain can receive solids, trash, or grit that could plug piping, such as the following locations:

1. Toilet rooms in commercial buildings should be equipped with floor drains with sediment buckets to facilitate cleaning.

2. Floor drains with sediment buckets must be provided in mechanical equipment rooms, where pumps, boilers, water chillers, heat exchangers, and HVAC equipment regularly discharge and /or must be periodically drained for mainte-nance and repairs. HVAC equipment requires the drainage of condensate from cooling coils using indirect drains.

3. Boilers require drains with sediment buckets. Strategically located floor drains are also required in buildings with wet fire-protection sprinkler systems to drain water in case sprinkler heads are activated. The maximum temperature of liquids discharged should be 140°F (60°C).

Floor drains shall connect to a trap so constructed that it can be readily cleaned and sized to serve efficiently the purpose for which it is intended. A deep-seal-type trap or an approved automatic priming device should be provided. The trap shall be accessible either from the floor-drain inlet or by a separate clea-nout within the drain. Figure 6 illustrates several types of drains that meet these conditions.

(A) Removable Grate; (B) Rust-Resistant Bolts; (C) Integral, One-Piece, Flashing Ring; (D) Cast Drain Body with Sump; (E) Sediment Bucket (optional).

Figure 4 Basic Floor-Drain Components:

(a) Sharp Edge, (b) Reverse Pattern

(a)

(b)

Figure 5 Pattern Draft for Floor Gratings

(A) Typical Drain with Integral Trap that May Be Cleaned Through Removable Strainer at Floor Level; (B) Floor Drain with Combination Cleanout and Backwater Valve, for Use Where Possibility of Backflow Exists; (C) Drain with Combined Cleanout, Backwater Valve, and Sediment Bucket.

Figure 6 Types of Floor Drain




ACCESSORIESA variety of accessories are available to make the basic drain adaptable to various types of structures. The designer must know the construction of the building, particularly the floor and deck structures, to specify the appropriate drain.

BACKWATER VALVESA backwater valve can be installed on a building sewer/house drain when the drain is lower than the sewer line, when unusual sewer surcharges may occur due to combined storm water and sanitary sewer systems, or when old municipal sewers incur high rates of infiltration. A backwater valve reacts similarly to a check valve. The device consists of a mechanical flapper or disc, which requires a certain amount of maintenance; therefore, attention must be given during the placement of these devices to a free area and access for maintenance. Sediment can accumulate on the flapper valve seat, preventing the flapper from closing tightly. Also, many valves employ a spring or mechanical device to exert a positive pressure on the flapper device, which requires occasional lubrication. Most manufacturers of backwater valves provide an access cover plate for maintenance, which may also be used as a building sewer cleanout.

Figure 7 illustrates various types of backwater valves that may be installed where there is a possibility of backflow.

OIL INTERCEPTORSIn commercial establishments such as service stations, garages, auto repair shops, dry cleaners, laundries, industrial plants, and process industries having machine shops, metal-treating process rooms, chemical process or mixing rooms, etc., there is always the problem of flammable or volatile liquids entering the drainage system, which can contaminate the sewer line and cause a serious fire or explosive condition.

Oil interceptors are designed to separate and collect oils and other light-density, volatile liquids, which would otherwise be discharged into the drainage system. An oil interceptor is required wherever lubricating oil, cutting oil, kerosene, gaso-line, diesel fuel, aircraft fuel, naphtha, paraffin, trisodium phos-phate, or other light-density and volatile liquids are present in or around the drainage system.

The interceptor is furnished with a sediment bucket, which collects debris, small parts, chips, particles, and other sediment that are frequently present in industrial waste from these types of facilities and could clog the drainage system. A gasketed, removable cover permits access for cleaning the interceptor. To eliminate pressure buildup inside the interceptor, a connection on each side of the body allows venting of the interceptor.

Oil interceptors are sized in accordance with the maximum anticipated gpm (L/s) flow rate of wastewater that could be

discharged through a tailpiece and are typically protected from back-siphonage by the vacuum breaker mounted at the tailpiece entrance.

Fixture wastewater type. These devices are mounted on the trap of frequently used fixtures. A tapping at the overflow line will allow small amounts of wastewater to enter an adjacent, infrequently used drain as the trap surges during use.

Automatic trap primers can be obtained as pre-engineered devices, which have widely accepted approval. All direct con-nections between the sewer system and the potable water system must be protected from potential contamination. The above-referenced primers can be manufactured, or fitted with, devices that are approved to prevent cross-contamination.

SUPPORTSThe location of pipe supports is usually specified by code. They are located to maintain a slope that is as uniform as possible and will not change with time. In this regard, the rigidity of pipe and joints and the possibility of creep and bedding settlement are primary considerations. When building settlement may be significant, special hanging arrangements may be necessary. Underground piping should be continuously and firmly sup-ported, but blocking below metal pipe is usually acceptable. Consult the manufacturer for recommendations for piping materials not covered in the code and for special problems.

Hangers should be designed adequately. To protect from damage by building occupants, allow at least a 250-lb (113.4-kg) safety factor when designing hangers. See Data Book, Volume 4, Chapter 6 for further information.

Seismic restraint must also be considered.

MATERIALS

PIPINGMaterials recommended for soil and waste piping, installed aboveground within buildings, are copper alloy, copper, cast iron (hub-and-spigot or hubless), galvanized steel, or PVC plas-tic pipe. Underground building drains should be cast-iron soil pipe, hard-temper copper tube, ABS or PVC, PVDF, DWV pattern Schedule 40 plastic pipe with compression joints or couplings,

Figure 7 Various Types of Backwater Valve

Figure 8 Combination Floor Drain and Indirect Waste Receptor



installed with a minimum cover of 12 in. (300 mm). Corrosive wastes require suitably acid-resistant materials such as high-silicon cast iron, borosilicate glass, polypropylene, etc. (Note: Some blood analyzers discharge sodium azide, which forms a very dangerous, explosive compound with copper pipes. Either other piping must be used or the sodium azide must be kept out of the system.) The materials used for pipe fittings must be com-patible with the materials utilized for piping. Fittings should slope in the direction of flow and have smooth interior surfaces without ledges, shoulders, or reductions that may obstruct the flow in piping.

Drains specified with cast-iron or PVC bodies should be suit-able for most installations. Where extra corrosion resistance is required, high-silica cast iron, polypropylene, borosilicate glass, stainless steel, galvanized iron, or other acid-resisting material should be selected. Where a sediment bucket is used, it should be bronze or galvanized or stainless steel. Enameled sediment buckets are impractical because they chip when cleaned.

In the selection of materials for top surfaces, such as grates, where floor drains are visible in finished areas, appearance is a prime consideration. As cast iron will rust and galvanizing and chrome plating will eventually be worn off by traffic, the pre-ferred material is solid, cast nickel-bronze, which maintains its attractive appearance. In a swimming pool, however, chlorine necessitates the use of chlorine-resistant materials. For large grates that will be subject to hand-truck or forklift traffic, a duc-tile iron grate with or without a nickel-bronze veneer is recom-mended.

Polished brass or bronze for floor service has the disadvan-tage of discoloring unless there is constant traffic over it. Cast aluminum has also been found inadequate for certain floor-service applications due to excessive oxidation and its inability to withstand abrasion.

jOINING METHODSDrain and cleanout outlets are manufactured in five basic types:

1. Inside caulk. In this arrangement, the pipe extends up into the drain body and oakum is packed around the pipe tightly against the inside of the outlet. Molten lead is then poured into this ring and later stamped or caulked to correct for lead shrinkage. Current installation methods use a flexible gasket for a caulking material. See Figure 9.

2. Spigot outlet. This type utilizes the caulking method as out-lined above, except that the spigot outlet is caulked into the

hub or bell of the downstream pipe or fitting. See Figure 1-10.

3. Push-seal gasketed outlet. This type utilizes a neoprene gasket similar to standard ASTM C564 neoprene gaskets approved for hub-and-spigot, cast-iron soil pipe. A ribbed neoprene gasket is applied to the accepting pipe, thus allowing the drain outlet to be pushed onto the pipe.

4. No-hub. This type utilizes a spigot (with no bead on the end) that is stubbed into a neoprene coupling with a stainless-steel bolting band (or other type of clamping device), which, in turn, accepts a downstream piece of pipe or headless fitting. See Figure 11.

5. IPS or threaded. This type is a tapered female thread in the drain outlet designed to accept the tapered male thread of a downstream piece of pipe or fitting. See Figure 12.

Figure 9 Inside-Caulk Drain Body

Figure 10 Spigot-Outlet Drain Body

Figure 12 IPS or Threaded – Outlet Drain Body

Figure 11 No-Hub-Outlet Drain Body




NOISE TRANSMISSIONAvoiding direct metal-to-metal connections may reduce noise transmission along pipes. Using heavier materials generally reduces noise transmission through pipe walls. Isolating piping with resilient materials, such as rugs, belts, plastic, or insulation may reduce noise transmission to the building. See Table 9 for relative noise-insulation absorption values.

BUILDING SEWER INSTALLATIONThe installation of building sewers is very critical to the opera-tion of the sewer. Inadequate bedding in poor soils may allow the sewer to settle, causing dips and low points in the sewer. The settlement of sewers interrupts flow, diminishes minimum cleansing velocity, reduces capacity, and creates a point where solids can drop out of suspension and collect.

The following are some guidelines for installing building sewers:

1. Compacted fill. Where natural soil or compacted fill exists, the trench must be excavated in alignment with the proposed pitch and grade of the sewer. Depressions need to be cut out along the trench line to accept the additional diameter at the piping joint or bell hub. A layer of sand or pea gravel is placed as a bed in the excavated trench because it is easily compacted under the pipe, allowing more accurate align-ment of the pipe pitch. The pipe settles into the bed and is firmly supported over its entire length.

2. Shallow fill. Where shallow amounts of fill exist, the trench can be over-excavated to accept a bed of sand, crushed stone, or similar material that is easily compacted. Bedding should be installed in lifts (layers), with each lift compacted to en-sure optimum compaction of the bedding. The bed must be compacted in alignment with the proposed pitch and grade of the sewer. It is recommended that pipe joints or bell hub depressions be hand-prepared due to the coarse crushed stone. The soil-bearing weight determines trench widths and bedding thickness.

3. Deep fill. Where deep amounts of fill exist, the engineer should consult a geotechnical engineer, who will perform soil borings to determine the depths at which soils with proper bearing capacities exist. Solutions include compact-

ing existing fill by physical means or removing existing fill and replacing it with crushed stone structural fill.

4. Backfilling. Backfilling of the trench is just as critical as the compaction of the trench bed and the strength of existing soils. Improper backfill placement can dislodge pipe and cause uneven sewer settlement, with physical depressions in the surface. The type of backfill material and compac-tion requirements need to be reviewed to coordinate with the type of permanent surface. Landscaped areas are more forgiving of improper backfill placement than hard surface areas such as concrete or bituminous paving.

Care must be taken when using mechanical means to com-pact soils above piping. Mechanical compaction of the first layer above the pipe by vibrating or tamping devices should be done with caution. Compacting the soil in 6-in. (150-mm) layers is recommended for a good backfill.

Proper sewer bedding and trench backfill will result in an instal-lation that can be counted upon for long, trouble-free service.

SANITATIONAll drains should be cleaned periodically, particularly those in markets, hospitals, food-processing areas, animal shelters, morgues, and other locations where sanitation is important.

Where sanitation is important, an acid-resisting enameled interior in floor drains is widely accepted. The rough surfaces of either brass or iron castings collect and hold germs, fungus-laden scum, and fine debris that usually accompany drain waste. There is no easy or satisfactory way to clean these rough surfaces. The most practical approach is to enamel them. The improved sanitation compensates for the added expense. How-ever, pipe threads cannot be cut into enameled metals because the enameling will chip off in the area of the machining. Also, pipe threads themselves cannot be enameled; therefore, caulked joints should be specified on enameled drains. Most adjustable floor drains utilize threaded adjustments. The drains cannot be enameled because of this adjusting thread. However, there are other adjustable drains that use sliding lugs on a cast thread and may be enameled.

Another point to remember is that a grate or the top ledge of a drain can be enameled, but the enamel will not tolerate traf-fic abrasion without showing scratches and, eventually, chip-ping. The solution to this problem is a stainless-steel or nickel-bronze rim and grate over the enameled drain body, a common practice on indirect waste receptors, sometimes referred to as “floor sinks.” Specifiers seem to favor the square, indirect waste receptor, but the round receptor is easier to clean and has better anti-splash characteristics. For cases where the choice of square or round is influenced by the floor pattern, round sinks with square tops are available.

In applications such as hospital morgues, cystoscopic rooms, autopsy laboratories, slaughterhouses, and animal dens, the enameled drain is fitted with a flushing rim. This is most advis-able where blood or other objectionable materials might cling to the sidewalls of the drain.

Where the waste being drained can create a stoppage in the trap, a heel inlet on the trap with a flushing connection is rec-ommended in addition to the flushing rim, which merely keeps the drain sides clean. (This option may not be allowed by cer-tain codes.) A 2-in. (50-mm) trap flushes more effectively than a 3-in. (80-mm) trap because it allows the flushing stream to drill through the debris rather than completely flush it out. A

Table 9 Relative Properties of Selected Plumbing Materials for Drainage Systems

MaterialsNoise

AbsorptionCorrosion

Resistancea

ABS Fair GoodCast iron Excellent GoodClay b ExcellentConcrete c Faird

Copper Fair GoodGlass borosilicate b ExcellentPolypropylene Fair ExcellentPVC Fair ExcellentSilicon iron c ExcellentSteel, galvanized Good Fair

a This refers to domestic sewage. Consult manufacturer for resistance to particular chemicals.

b Since these materials are used only aboveground for chemical waste systems, this is not applicable.

c This material is usually allowed only belowground.d Susceptible to corrosion from hydrogen sulfide gas.



valve in the water line to the drain is the best way to operate the flushing-rim drain. Flush valves have been used and save some water; however, they are not as convenient or effective as a shut-off valve. In any flushing water-supply line to a drain, a vacuum breaker installed according to code must be provided.

KITCHEN AREASWhen selecting kitchen drains, the designer must know the quantity of liquid and solid waste the drains will be required to accept, as well as which equipment emits waste on a regular basis and which produces waste only by accidental spillage.

Floor-cleaning procedures should be ascertained to deter-mine the amount of water used. If any amount of solid waste is to be drained, receptors must be specified with removable sedi-ment buckets made of galvanized or stainless steel. Also, there must be enough vertical clearance over these drains to conve-niently remove the sediment buckets for cleaning.

Many kitchen planners mount kitchen equipment on a 5-in. (125-mm) curb. Placing the drain on top of the curb and under the equipment makes connection of indirect drain lines diffi-cult and the receptor inaccessible for inspection and cleaning. Mounting the receptor in front of the curb takes up floor space, and the myriad of indirect drains that discharge into it create a potential hazard for employees who may trip over them. The solution requires close coordination between the engineer and the kitchen designer. Figure 1-8 shows an arrangement whereby any spillage in front of the curb can be drained by half of the receptor, while indirect drains are neatly tucked away.

Where equipment is on the floor level and an indirect waste receptor must be provided under the equipment, a shallow bucket that can easily be removed is recommended.

WATERPROOFINGWhenever a cast-iron drain is cemented into a slab, separation due to expansion and contraction occurs and creates several problems. One is the constant wet area in the crevice around the drain that promotes mildew odor and the breeding of bac-teria. Seepage to the floor below is also a possibility. A seepage or flashing flange can correct this problem. Weep holes in the flashing flange direct moisture into the drain. Also, this flange accepts membrane material and, when used, the flashing ring should lock the membrane to the flange.

One prevalent misconception about the flashing flange is that it can have weep holes when used with cleanouts. In this case, there can be no weep holes into the cleanout to which the mois-ture can run. Weep holes should also be eliminated from the flashing flanges of drains, such as reflection-pool drains, where an overflow standpipe to maintain a certain water level shuts off the drain entrance.

The term “non-puncturing,” used in reference to membrane-flashing, ring-securing methods, is now obsolete, as securing bolts have been moved inboard on flashing L flanges and the membrane need not be punctured to get a seal. Of the various arrangements, this bolting method allows the greatest squeeze pressure on the membrane.

FLOOR LEVELINGA major problem in setting floor drains and cleanouts occurs when the concrete is poured level with the top of the unit, ignor-ing the fact that the addition of tile on the floor will cause the drain or cleanout to be lower than the surrounding surface. To solve the problem, cleanouts can be specified with tappings in

the cover rim to jack the top part of the cleanout up to the fin-ished floor level. Floor drains can be furnished with adjustable tops to attain an installation that is flush with the finished floor.

THERMAL EXPANSIONWhen excessive thermal expansion is anticipated, pipe move-ment should be controlled to avoid harmful changes in slope or damage. Anchoring, using expansion joints, or using expansion loops or bends may do this. When anchoring, avoid excessive stress on the structure and the pipe. Piping or mechanical engi-neering handbooks should be consulted if stress analysis is to be performed due to excessive stresses or to the differing expan-sion characteristics of materials.

PROTECTION FROM DAMAGEFollowing are some common types of damage to anticipate and some methods of protection:

Hazard Protection

Abrasion Plastic or rubber sleeves. Insulation where copper pipe leaves slab.

Condensation Insulation on piping.

Corrosion See Plumbing Engineering Design Handbook, Vol. 1, Ch. 8: Corrosion.

Earth loads Stronger pipe or pipe sleeves.

Expansion and contraction

Flexible joints, loops, swing joints, or offsets.

Fire Building construction around pipe. Some jurisdictions require metal piping within 2 ft (0.6 m) of an entry into a firewall. Must maintain fire ratings.

Heat Keeping thermoplastic pipe away from sources of heat or using insulation.

Nails Using ferrous pipe, steel sleeves, steel plates, or space pipe away from possible nail penetration zone.

Seismic Bracing pipe and providing flexible joints at the connection between piping braced to walls or structure and piping braced to the ceiling and between stories (where there will be differential movements).

Settlement Sleeves or flexible joints. When embedded in concrete, covering with three layers of 15-lb (6.8-kg) felt.

Sunlight Protecting thermoplastic pipe by insulation and jacket or shading to avoid warping.

Vandals Installing pipe above reach or in areas protected by building construction. Piping needs to be supported well enough to withstand 250 lb (113.4 kg) hanging on the moving pipe.

Wood Shrinkage Providing slip joints and shrinkage clearance for pipe when wood shrinks. Approximately 5⁄8 in. (16 mm)/floor is adequate for usual frame construction, based on 4% shrinkage perpendicular to wood grain. Shrinkage along the grain does not usually exceed 0.2%.

ALTERNATE SANITARY SYSTEMSThe design and installation of alternative engineered plumbing systems is permitted in all codes. A licensed professional engi-neer who is responsible for the proper operation of the system must design them. The most important consideration is that if an alternative system is contemplated, submission to, and approval by, the authorities having jurisdiction must be obtained. In order to expedite approval, the following is suggested:

1. Indicate on the design documents that the plumbing system, or parts thereof, is an alternative design.




2. Submit enough technical data to support the proposed al-ternative design and prove the system conforms to the intent of the code. This shall include suitability for the intended purpose, strength, equivalent level of performance compared to traditional installations, safety, and quality of materials.

3. The design documents shall include floor plans, riser dia-grams, and an indication of the proposed flow.

4. Assurance that manufacturers’ installation instructions will be adhered to.

5. If approval is given, the permit and all construction applications shall indicate an alternative engineered design is part of the approved installation.

The alternative systems are characterized by, but not limited to, using a single stack for both sanitary and vent or no vent at all. One exception is a conventional drainage, reduced vent system. All of the following described systems have been successfully used in the United States and in other parts of the world for many years and have proven effective in actual use.

All of the alternative systems to be dis-cussed have combined sanitary and vent. Because it is considered appropriate, they have been included in the sanitary drainage system chapter.

SOVENT SYSTEMThe Sovent system was developed in 1959 in Switzerland. It is a patented, single-stack, combination drainage and vent system that uses a single stack instead of a conventional two-pipe drainage and vent stack. The Sovent system uses copper pipe and is suitable only for multistory buildings because it will allow substantial economy in piping instal-lation. Although installed in many countries throughout the world, it remains an alter-native, unconventional system with only limited usage in the United States. It shall conform to ANSI B-16.45 and CISMA Stan-dard 177. It is not the intent of this chapter to provide specific design criteria for a Sovent system, but rather to discuss the individual component characteristics that will enable a plumbing engineer to obtain a working knowledge of how the Sovent system works. A typical Sovent-Stack system is illustrated in Figure 13.

The entire Sovent system consists of three principal parts: copper DWV piping for all branch wastes and stacks, an aerator fitting at each floor level where the branch waste line connects to the stack, and a deaerator fitting at the base of a stack where a stack enters the house drain.

The starting point is the horizontal soil and waste branches. The fixture units and branch sizes are similar to those figures found in

conventional systems. The maximum fixture units that may be connected to a branch or stack are also similar to that of conven-tional systems. Branch sizes must be increased one size where the following exists:

1. A second vertical drop or a vertical drop of more than 3 ft (0.9 m) requires an increase in the downstream side of the connection.

Figure 13 (A) Traditional Two-Pipe System, (B) Typical Sovent Single-Stack Plumbing System.

(A)(B)



2. When three 90-degree changes in direction occur in a hori-zontal branch, the horizontal branch shall be increased in size at the upstream side of the third change.

3. When a branch serves two water closets and one or more ad-ditional fixtures, the soil line shall be increased to 4 in. (100 mm) at the point where one water closet and one additional fixture are connected.

4. When a soil branch exceeds 12 ft (3.7 m) in horizontal length.

5. When a waste line exceeds 15 ft (4.6 m) in horizontal length.

Stacks must be carried full size through the roof. Two stacks can be connected at the top above the highest fixture. Two stacks may also be combined at the bottom prior to entering the build-ing drain. The size is based on the total fixture units. Fixtures may be connected into a horizontal offset in a stack below the deaerator fitting.

An aerator fitting is required at each level where a soil branch, a waste line the same size as the stack, or a waste branch one size smaller than the stack is connected. It consists of an upper stack inlet, a mixing chamber, and a baffle in the center of the fitting. This provides a chamber where the flow from the branches may gradually mix smoothly with the air and liquid already flow-ing in the stack. It also limits the turbulence and velocity of the entering water. A 2-in. (50-mm) horizontal branch may enter the stack with no fitting. There are two basic styles of aerator fitting that meets the needs of most design conditions: the double-side entry fitting and the single-entry fitting. Face entry and top entry are used in special cases.

A deaerator fitting is required at the bottom of a stack and is designed to overcome the tendency of the falling waste to build up excessive back pressure at the bottom of the stack when the flow is decelerated by the bend into the horizontal drain. It con-sists of an air separation chamber, a nose piece, a pressure relief outlet at the top connected to the building drain, and a stack outlet at the bottom. The purpose of the deaerator is to separate the air flow from the stack and ensure the smooth flow of liquid into the building drain and to relieve the positive pressure gen-erated at the stack’s base. The configuration of the fitting causes part of the air falling with the liquid to flow through the pres-sure relief line, and the remainder of the air goes directly into the building drain.

There is great importance in explaining the special require-ments of the Sovent system to the installing contractor. It is probable the contractor is unfamiliar with this system and a complete explanation will be necessary. The engineer should make regular inspections of the project to assure the design conditions are met. A complete set of contract documents shall be provided to the owner to allow proper alteration or expan-sion of the project in the future.

For additional information and specific sizing contact the Copper Development Association.

SINGLE-STACK SYSTEMThe single-stack system is a combination drainage and vent system consisting of a single stack instead of conventional sepa-rate drainage and vent stacks. This drainage system is one where the drainage stack shall serve as both a single-stack drainage and vent system when properly sized. The relief of internal air pressure depends on making the one-pipe system larger than

that required for drainage purposes alone. The drainage stack and branch piping shall be considered as vents for the drainage system as a whole. Although the pipe sizing is larger in a single-stack system than in a conventional one, installation savings are achieved by reducing the amount of vent piping required.

The major components of the one pipe system are oversize, unvented S traps instead of the conventionally sized and vented P traps and fixtures that allow water to run off after the tap is closed to fill the traps with water to maintain the trap seal. The trap arm length is limited to reduce any suction buildup, and the stack is oversized to limit the internal air pressure and vacuum buildup.

Often referred to as the “Philadelphia” code, this unconven-tional system has successfully operated for more than 100 years with no problems. Consideration has been made by code bodies to include this system as an engineered design, which allows this to be used providing an engineer has designed it in accordance with code. For further information, contact the Philadelphia building department. A riser diagram of a typical Philadelphia System is illustrated in Figure 13.

REDUCED-SIzE VENTINGIn 1974, the National Bureau of Standards (NBS) conducted a laboratory study of one-story and split-level experimental drain-age systems where the vents varied from one to six pipes smaller than those for conventional systems. They showed satisfactory hydraulic and pneumatic performance under various loading conditions. At the same time, the 10-story wet vent system at the Stevens Building Technology Research Laboratory had been modified by reducing the vents one to three pipe sizes in accor-dance with the plans and specifications of the NBS and reducing the size of the vents. The results also indicated that the vents in a two-story housing unit can safely be made smaller than pres-ently allowed without jeopardizing the trap seals.

This system may allow economies of pipe size in the venting design of low-rise residential buildings, although this particu-lar system has not been accepted by authorities. It is limited to special conditions and requires the vent pipes be of a material such as copper or plastic that will resist the buildup of products of corrosion.

VACUUM DRAINAGE SYSTEMVacuum drainage operates on the principal of having the major-ity of the system under a continuous vacuum. The system is proprietary and is made by various manufacturers. The differ-ent manufacturers have different names for devices performing similar operations, so generic identification is used. There are various designs capable of sanitary and waste disposal, either separate or in combination, and are used for various projects such as prisons, supermarkets, and ships. There is no direct con-nection from the sanitary waste to the vacuum system. The one big advantage is that piping is installed overhead and no pipe is required to be placed underground.

The system consists of three basic components: a vacuum network of piping and other devices that collects and transports waste from its origin, vacuum generation pumps, and a vacuum interface device at the point of origin that isolates the vacuum piping from atmospheric pressure. When the system is to serve water closets, the water closets must be purpose made, designed to rinse and refill with ½ gallon (2.2 L) of water.

The piping network for a vacuum waste system is held under a constant vacuum between 12 and 18 in. of mercury (in Hg)




(40–65 kPa) and is generally fabricated from PVC, copper, or other nonporous, smooth-bore material. Horizontal piping shall slope at a rate of 1/8 in. per foot (1.18 mm) toward the vacuum center. This piping slope is just as it is in conventional systems. If this slope cannot be maintained, the traps created in the piping runs when routed around obstacles would be cleared because of the differential pressure that exists between the vacuum center and the point of origin. The discharge of the piping system is into the waste storage tanks.

The vacuum generation system includes the vacuum pumps that create a vacuum in the piping and storage tanks that col-lect and discharge the waste into the sewer system. The vacuum pumps run only on demand and redundancy is provided. They also have sewage pumps that pump the drainage from the stor-age tank(s) into the sewer.

The vacuum interface is different for sanitary drainage than for clear waste similar to that of supermarkets. Water closet and gray water waste are separate. The vacuum toilets operate instantly upon flushing. When a vacuum toilet is cycled, a dis-charge control panel assembly is activated sending the discharge to the tank. A valve acts as an interface between the vacuum and the atmosphere controls gray water. It is designed to collect a given amount of the water and then activate, sending the drain-age into the tank. The tank will discharge into the sewer when a predetermined level is reached.

When clear water is discharged from a project like a super-market, the water from cases, etc. goes into an accumulator. When a controller senses sufficient waste is present, it opens the normally closed extraction valve, which separates the atmo-spheric pressure from the vacuum, and removes the waste from the accumulator.

Because the vacuum toilets use 0.5 gallon/flush as compared to 3.5 gallons/flush (1.9 L to 13 L) from a conventional system, the holding tanks could be smaller. There is also a flush control panel designed to provide all the control functions associated with vacuum toilets. The control panel consists of a flush valve, flush controller, water valve, and vacuum breaker. All controls are pneumatically operated. The flush controller controls the opening of the flush valve and the rinse valve as well as the duration of the time the flush valve is open.

REFERENCES

1. Daugherty, Robert L., Joseph B. Franzini, and E. John Finnemore. 1985. Fluid mechanics with engineering applica-tions. 8th ed. New York: McGraw-Hill.

2. Dawson, F.M., and A.A. Kalinske. 1937. Report on hydraulics and pneumatics of plumbing drainage systems. State Univer-sity of Iowa Studies in Engineering, Bulletin no. 10.

3. Wyly and Eaton. 1950. National Bureau of Standards, Housing and Home Finance Agency.



About This Issue’s ArticleThe November 2007 continuing education article is “Sani-tary Drainage Systems,” Chapter 1 of ASPE’s Plumbing Engi-neering Design Handbook Volume 2: Plumbing Systems.

The purpose of the sanitary drainage system is to remove ef-fluent discharged from plumbing fixtures and other equip-ment to an approved point of dis posal. A sanitary drainage system generally consists of horizontal branches, vertical stacks, a building drain inside the building, and a building sewer from the building wall to the point of disposal. The discussion in this chapter cen ters only on the design of drain and waste systems.


PSD

142


CE Questions—“Sanitary Drainage Systems” (PSD 142)1. A vertical pipe that carries away clear water waste

from equipment and non-sanitary fixtures is called a _________.a. sanitary stackb. soil stackc. waste stackd. water stack

2. The generally accepted pressure in a sanitary drainage system is _________.a. +/– 0.1 inch of water columnb. +/– 1 inch of water columnc. +/– 10 inches of water columnd. +/– 100 inches of water column

3. Who originally proposed using drainage fixture units to represent a fixture’s load-producing effect on the plumbing system?a. F.M. Dawsonb. Wyly and Eatonc. Roy B. Hunterd. none of the above

4. What is the recommended drainage fixture unit load for a single lavatory?a. 1, b. 2, c. 3, d. 4

5. Which common formula for calculating flow in pipes is meant for open-channel flow?a. Hazen and Williamsb. Manning c. Darcy-Weisbachd. none of the above

6. Which of the following is designed to transport sanitary waste and larger solids suspended in the effluent?a. storm sewerb. sump pumpc. ejector pumpd. manhole

7. Cleanouts should be provided _________.a. at the base of all stacksb. at every change in direction greater than 45 degreesc. at the roof stack terminald. all of the above

8. Which of the following is not a basic floor drain component?a. sediment bucketb. removable gratec. air-admittance valved. cast drain body with sump

9. In a basic floor drain assembly, the _________ pre vents water from passing around the drain to the area below.a. flashing ringb. sediment bucketc. grated. strainer

10. The recommended material for a sediment bucket is _________.a. bronze b. galvanized steelc. stainless steeld. all of the above

11. Which of the following pipe materials offers excellent noise absorption?a. ABSb. cast ironc. PVCd. galvanized steel

12. The single-stack system is also referred to as the _________ system.a. Soventb. Philadelphiac. vacuum drainaged. none of the above







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PSD

130

Valves


NOVEMBER/DECEMBER 2005

PSDMAGAZINE.ORG



Reprinted from American Society of Plumbing Engineers Data Book Volume 4: Plumbing Components and Equipment, Chapter 3: Valves. © 2003, American Society of Plumbing Engineers.

Valvesservethepurposeofcontrollingthefluidsinbuildingser-vice piping. They come inmany shapes, sizes, design types, andmaterialstoaccommodatedifferentfluids,piping,pressureranges,andtypesofservice.Properselectionisimportanttoensurethemostefficient,cost-effective,andlong-lastingsystems.Nosinglevalveisbest for all services. This chapter is limited tomanually operatedvalvesthatstart,stop,andregulateflow,andpreventitsreversal.

FunctionsValvesaredesignedtoperformfourprincipalfunctions:1. Startingandstoppingflow

2. Regulating(throttling)flow

3. Preventingthereversalofflow

4. Regulatingorrelievingtheflowpressure.

Service Considerations1. Pressure

2. Temperature

3. Typeoffluid

A. LiquidB. Gas,i.e.,steamorairC. Dirtyorabrasive(erosive)D. Corrosive

4. Flow

A. On-offB. ThrottlingC. NeedtopreventflowreversalD. ConcernforpressuredropE. Velocity

5. Operatingconditions

A. FrequencyofoperationB. AccessibilityC. Overallspace/sizeavailableD. ManualorautomatedcontrolE. Needforbubble-tightshut-offF. ConcernsaboutbodyjointleaksG. FiresafedesignH. Speedofclosure.

Approvals1. ManufacturersStandardizationSociety(MSS)

2. Fireprotection:ULandFactoryMutual(FM)

3. Stateandlocalcodes

4. AmericanPetroleumIndustries(API).

Types of Valve

Gate ValveWithstartingandstopping flow itsprime function, thegatevalveisintendedtooperateeitherfullyopenorfullyclosed.Whenfullyopen,ithastheleastresistancetoflowofallthevalvetypes.

From an examination of Figure 1, it becomes readily apparenthowthegatevalvegotitsname.Agate-likedisc,actuatedbyastemscrewandhandwheel,movesupanddownatrightanglestothepathofflowandseatsagainsttwofacestoshutoffflow.Asthediscofthegatevalvepresentsaflatsurfacetotheoncomingflow,thisvalve is not suited for regulating or throttling flow. Flow through

apartiallyopengatevalvecre-ates vibration and chatteringand subjects the disc and seattoinordinatewear.

There is a wide variety ofseatsanddiscstosuitthecon-ditions under which the valveistooperate.Forrelativelylowpressures and temperaturesand forordinary fluids, seatingmaterials are not a particularlydifficult problem. Bronze andironvalvesusuallyhavebronzeor bronze-faced seating sur-faces; iron valves may be alliron.Nonmetallic“composition”discsareavailablefortightseat-ingorhard-to-holdfluids,suchasairandgasoline.

Gate discs can be classifiedas solid-wedge discs, doublediscs or split-wedge discs. Inthesolid-wedgedesign,asingletapereddisc,thinatthebottomandthickeratthetop,isforcedintoasimilarlyshapedseat.

Inthedoubleandsplit-wedgediscdesigns,twodiscsareemployedbacktoback,withaspreadingdevicebetweenthem.Asthevalvewheelisturned,thegatedropsinto its seat (aswithanyothergatevalve),buton the final turnsof the wheel, the spreaderforces the discs outwardagainst the seats, effectingtighterclosure.

Bypass valves should beprovidedwherethedifferen-tialpressureexceeds200psi(1378kPa)onvalvessized4to6in.(101.6to152.4mm),and 100 psi (689 kPa) onvalves 8 in. (203.2 mm) orlarger.Bypassvalves shouldbe1/2in.(12.7mm)for4-in.(101.6-mm)valves,and¾in.(19.1mm)for5-in.(127-mm)valvesorlarger.

Globe ValveThe globe valve (which isnamed for the shape of itsbody)ismuchmoreresistantto flow than thegatevalve,ascanbeseenbyexaminingthe path of flow through it(Figure 2). Its main advan-tagesoverthegatevalveare

Valves

Figure GlobeValve

Figure1 GateValve

50 PlumbingSystems&Design • Nov/Dec 2005


itsuseasathrottlingvalvetoregulateflowanditseaseofrepair.

Because all contact between seat anddiscendswhen flowbegins, theeffectsofwiredrawing(seaterosion)areminimized.The valve can operate just barely open orfullyopenwith littlechange inwear.Also,becausethediscoftheglobevalvetravelsarelativelyshortdistancebetweenfullyopenand fully closed, with fewer turns of thewheelrequired,anoperatorcangaugetherateof flowbythenumberof turnsof thewheel.

Aswiththegatevalve,thereareanumberof disc and seat arrangements. These areclassified as conventional disc, plug type,andcompositiondisc.

The conventional disc is relatively flat,with beveled edges. On closure itispusheddownintoabeveled,cir-cularseat.

Plug type discs differ onlyin that they are far more tapered,thereby increasing the contact sur-face between disc and seat. Thischaracteristic has the effect ofincreasing their resistance to thecutting effects of dirt, scale, andotherforeignmatter.

The composition disc differsfrom theothers in that itdoesnotfit into the seat opening but overit,muchasabottlecapfitsoverthebottleopening.Thisseatadaptsthevalvetomanyservices, including use with hard-to-holdsubstances such as compressed air, andmakesiteasytorepair.

Angle ValveVerymuchakintotheglobevalve,theanglevalve (Figure 3) can cut down on pipinginstallation time, labor, and materials byserving as both valve and 90° elbow. It islessresistanttoflowthantheglobevalve,asflowmustchangedirectiontwiceinsteadofthreetimes.Itisalsoavailablewithconven-tional,plugtype,orcompositiondiscs.

Ball ValveThe ball valve derives its name from thedrilled ball that swivels on its vertical axisand is operated by a handle, as shown inFigure 4. Its advantages are its straight-through flow, minimum turbulence, lowtorque,tightclosure,andcompactness.Also,aquarterturnofthehandlemakesitaquick-

closingor-openingvalve.Reliability,easeofmaintenance,anddurabilityhavemadetheball valve popular in industrial, chemical,andgastransmissionapplications.

Butterfly ValveFigure5illustratesabutterflyvalve,thevalvemostcommonlyusedinplaceofagatevalveincaseswhereabsolute,bubble-freeshut-offis

required.Itismanufacturedinnominaldiam-etersfrom1to72in.(25.4to1828.8mm).

Inadditiontoitstightclosing,oneofthevalve’s advantages is that it can be placedintoaverysmallspacebetweenpipeflanges.Itisavailablewithseveraltypesofoperator,motorizedandmanual,andavarietyofcom-ponentmaterialcombinations.

Screwed-lug type valves should be pro-vided so that equipment may be removedwithoutdrainingdownthesystem.

Check ValveSwing checks and lift checks are themostcommon forms of check valve. Both aredesigned to prevent reversal of flow in apipe. The swing check, Figure 6, permitsstraight-through flow when open and is,

therefore,lessresistanttoflowthantheliftcheck.

Note: Awordofcautionregard-ing the swing check: There havebeeninstanceswhenaswingcheckstayedopenafewsecondsafterthereversalofflowbegan,allowingthevelocityofbackflowtorisetosucha point that, when closure finallydidoccur,itwasinstantaneousandthe resulting shock to the valveandsystemcausedseriousdamage.Goodinsuranceagainstsuchapos-sibility is a lever and weight or a

spring to ensure immediate closure uponreversalofflow.

The lift check, Figure 7, is primarily forusewithgasesorcompressedairorinfluidsystemswherepressuredropisnotcritical.

Valve MaterialsA single valve may be constructed of sev-eralmaterials.Itmayhaveabronzebody,amonelseat,andanaluminumwheel.Mate-rial specificationsdependon theoperatingconditions.

Figure5 ButterflyValve

Figure4 BallValve

Figure3 AngleValve

Figure SwingCheck

Nov/Dec 2005 • PlumbingSystems&Design 51


Brass and BronzeBrass usually consists of 85% copper, 5%lead, 5% tin, and 5% zinc. Bronze has ahigher copper content, ranging from 86 to90%,withtheremainingpercentagedividedamonglead,tin,andzinc.

Of particular importance is the zinccontent.Industrymaximumissetat15%,butcertainmilitaryandgovernmentspecificationsallownomorethan6%.

Under certain circumstances, a phe-nomenon known as “dezincification” willoccurinvalvesorpipescontainingzinc.Theaction is a result of electrolysis; in effect,thezincisactuallydrawnoutandremovedfromthebrassorbronze,leavingaporous,brittle, andweakenedmaterial. The higherthezinccontent,thegreaterthesusceptibil-itytodezincification.Tosloworpreventtheprocess,tin,phosphorusantimony,andotherinhibitorsareadded.Brassvalvesshouldnotbe used for operating temperatures above450°F (232.2°C). Themaximum for bronzein550°F(287.8°C).

IronIronusedinvalvesusuallyconformstoASTMStandardA26. Although iron-bodied valvesaremanufacturedinsizesassmallas¼-in.(6.4-mm) nominal diameter, they are mostcommonlystockedinsizesof2in.(50.8mm)andabove.Intheselargersizes,theyarecon-siderablylessexpensivethanbronze.

Thehigherweightofironvalves,ascom-paredtobronzevalves,shouldbeconsideredwhen figuring hanger spacing and loads.A typical 2-in. (50.8-mm) screwed, bronze,globe valve rated at 125 psi (861.3 kPa)weighsabout13lb(5.9kg).Thesamevalveinironweighs15lb(6.8kg)and,ifspecifiedwithayokebonnet,about22lb(10kg).

Malleable IronMalleable iron valves are stronger, stiffer,and tougher than iron-bodied valves andhold tighter pressures. Toughness is most

valuableforpipingsubjectedtostressesandshocks.

Stainless SteelFor highly corrosive fluids, stainless steelvalves provide the maximum corrosionresistance,highstrength,andgoodwearingproperties.Seatingsurfaces,stems,anddiscsofstainlesssteelaresuitablewhereforeignmaterials in the fluids handled could haveadverseeffects.

Valve RatingsMost valve manufacturers rate their prod-ucts in terms of saturated steam pressure;or pressure of nonshock cold water, oil,orgas (WOG);orboth.These ratingsusu-ally appear on the body of the valve. Forinstance, a valve with the markings “125”with“200WOG”willoperate safelyat 125psi(861.3kPa)ofsaturatedsteamor200psi(1378kPa)coldwater,oil,orgas.

Theengineershouldbefamiliarwiththemarkingsonthevalvesspecifiedandshouldkeep them in mind during constructioninspection. A ruptured valve can domuchdamage.

Valve Components

StemsStemdesignsfallintofourbasiccategories:rising stemwith outside screw, rising stemwithinsidescrew,nonrisingstemwithinsidescrew,andslidingstem.

Rising stem with outside screw Thisdesign is ideal where the valve is infre-quently used and the possibility of stick-ingwouldconstituteahazard,suchasinafire-protection system. In this arrangement,the screws are not subject to corrosion orelements in the line fluid thatmight causedamagebecausetheyareoutsidethevalvebody.Also,beingoutside,theycaneasilybelubricated.

Aswithanyother risingstemvalve, suf-ficientclearancemustbeallowedtoenableafullopening.

Rising stem with inside screw Thisdesign is the simplest and most commonstemdesignforgate,globe,andanglevalves.Thepositionofthehandwheelindicatesthepositionofthedisc,openedorclosed.

Nonrising stem These are ideal whereheadroom is limited. They are generallylimitedtousewithgatevalves.Inthistype,thescrewdoesnotraisethestembutratherraisesandlowersthedisc.Asthestemonlyrotatesanddoesnotrise,wearonpackingsisslightlylessened.

Sliding stem These are applied wherequickopening and closing are required.Alever replaces the hand wheel, and stemthreadsareeliminated.

BonnetsIn choosing valves, the service characteris-ticsofthebonnetjointshouldnotbeover-looked. Bonnets and bonnet joints mustprovide a leakproof closure for the body.Therearemanymodifications,butthethreemostcommontypesarescrewed-inbonnet,screwed union-ring bonnet, and boltedbonnet.

Screwed-in bonnet This is the simplestandleastexpensiveconstruction,frequentlyused on bronze gate, globe, and anglevalves and recommended where frequentdismantling is not needed. When properlydesignedwithrunningthreadsandcarefullyassembled, thescrewed-inbonnetmakesadurable,pressure-tightsealthatissuitedformanyservices.

Screwed union-ring bonnet This con-struction is convenient where valves needfrequent inspection or cleaning—also forquickrenewalorchangeoverofthediscincomposition disc valves. A separate unionringappliesadirect loadonthebonnettohold thepressure-tight jointwith thebody.Theturningmotionusedtotightentheringis split between the shoulders of the ringand bonnet.Hence, the point of seal con-tactbetweenthebonnetandthebodyislesssubjecttowearfromfrequentopeningofthejoint.

Contactfacesarelesslikelytobedamagedinhandling.Theunionringgivesthebodyaddedstrengthand rigidityagainst internalpressureanddistortion.

Whileidealonsmallervalves,thescrewed,union-ring bonnet is impractical on largesizes.

Bolted bonnet joint A practical andcommonlyusedjointforlargersizevalvesorforhigher-pressureapplications, theboltedbonnet joint has multiple boltings withsmaller diameter bolts that permit equal-izedsealingpressurewithout theexcessivetorqueneededtomakelargethreadedjoints.Onlysmallwrenchesareneeded.

End ConnectionsValves are availablewith screwed,welded,brazed, soldered, flared, flanged, and hubends.

Screwed EndThisisbyfarthemostwidelyusedtypeofend connection. It is found in brass, iron,steel,andalloypipingmaterials.Itissuitedfor all pressures but is usually confinedto smaller pipe sizes. The larger the pipesize,themoredifficultitistomakeupthescrewedjoint.

Welded EndThis type of end is available only in steelvalvesandfittingsandismainlyforhigher-pressureand-temperatureservices.Itisrec-

Continuing Education: Valves

Figure LiftCheck



ommended for linesnot requiring frequentdismantling.Therearetwotypesofweldedendmaterials:buttendsocketwelding.Butt-weldingvalvesandfittingscomeinallsizes;socket-welding ends are usually limited tosmallersizes.

Brazed EndThisisavailableonbrassmaterials.Theendsofsuchmaterialsarespeciallydesignedfortheuseofbrazingalloystomakethejoint.When the equipment and brazing materialareheatedwithaweldingtorchtothetem-perature requiredby the alloy, a tight sealis formed between the pipe and valve orfitting.Whilemade in amanner similar toasolder joint,abrazed jointcanwithstandhigher temperatures due to the brazingmaterialsused.

Soldered JointThisisusedwithcoppertubingforplumb-ingandheatinglinesandformanylow-pres-sureindustrialservices.Thejointissolderedbyapplyingheat.Becauseofcloseclearancebetweenthetubingandthesocketofthefit-tingorvalve,thesolderflowsintothejointbycapillaryaction.Theuseofsolderedjointsunderhightemperaturesislimitedbecauseofthelowmeltingpointofthesolder.Silversolderorsilfosareusedforhigherpressuresandtemperatures.

Flared EndThis is commonly used on valves and fit-tingsformetalandplastictubingupto2in.(50.8mm)diameter.Theendofthetubingisskirtedorflaredandaringnutisusedtomakeauniontypejoint.

Flanged EndThis is generally usedwhen screwed endsbecome impractical because of cost, size,strengthofjoint,etc.Flangedendsaregen-erallyused for larger-diameter linesdue toeaseof assembly anddismantling. Flangedfacings are available in various designsdepending on service requirements. Oneimportant rule is to match facings. Whenbolting iron valves to forged steel flanges,thefacingshouldbeoftheflatfacedesignonbothsurfaces.

Hub EndThisisgenerallylimitedtovalvesforwater-supply and sewage piping. The joint isassembledonthesocketprinciple,withthepipeinsertedinthehubendofthevalveorfittingthencaulkedwithoakumandsealedwithmoltenlead.

AbbreviationsAGA AmericanGasAssociationAISI AmericanIronandSteelInstituteANSI AmericanNationalStandardsInstituteAPI AmericanPetroleumInstitute

ASME AmericanSocietyofMechanicalEngineersASTM AmericanStandardforTestingandMaterialAWWA AmericanWaterWorksAssociationBUNA-N Butadieneandacryloni-trile (nitrilerubber)CSA CanadianStandardsAssociation(also CSAInternational)(approvalagencyforAGA)CWP ColdworkingpressureEPDM Ethylene-propylenedienemonomerIBBM Ironbody,bronzemounted(trim)IS InsidescrewMSS ManufacturersStandardizationSocietyoftheValveandFittingsIndustryNBR Acrylonitrile-butadienerubberNFPA NationalFireProtectionAssociationNRS NonrisingstemOS&Y OutsidescrewandyokePSI PoundspersquareinchPTFE PolytetrafluoroethyleneplasticRS RisingstemSWP SteamworkingpressureTFE TetrafluoroethyleneplasticWCB Wroughtcarbon,gradeBWOG Water,oil,gas(coldworkingpres-sure)WWP Waterworkingpressure

GlossaryBall Avalveconsistingofasingledrilled

ball that is operated by a handle attachedto the vertical axis of the ball, which per-mits fluid flow in a straight-through direc-tion.Theballwithinthevalvebodymayberotatedfullyopenedorfullyclosedbyonequarterturnofthehandle.

Body Thatpartofthevalvethatattachestothepipelineorequipment—withscrewedends,flangedends,orsoldered/weldedjointends—andenclosestheworkingpartsofthevalve.

Bonnet The part of the valve housingthroughwhichthestemextends.Itprovidessupport and protection to the stem andhousesthestempacking.Itmaybescrewedorboltedtothebody.

Butterfly A type of valve consisting ofa single disc that is operated by a handleattachedtothedisc,whichpermitsfluidflowinastraight-throughdirection.Thevalveisbidirectional.Thediscwithinthevalvebodymayberotatedfullyopenorfullyclosedbyonequarterturnofthehandle.

Cap The top part of the housing of acheckvalve(equivalent to thebonnetofagate or globe valve),whichmay be eitherscrewedorboltedontothemainbody.

Check valve An automatic, self-closingvalve that permits flow in only one direc-tion.Itautomaticallyclosesbygravitywhenliquidceasestoflowinthatdirection.

Clapper A common term that is usedtodescribethediscofaswingtype,checkvalve.

Disc The disc-shaped device that isattachedtothebottomofthestemandthatisbroughtintocontactwithorliftedofftheseating surfaces to close or open a globevalveorbutterflyvalve.

Flanged bonnet A type of bonnet soconstructed that it attaches to the bodybymeans of a flanged, bolted connection.Thewhole bonnet assembly, including thehandwheel,stem,anddisc,maybequicklyremoved by unscrewing the nuts from thebonnetstudbolts.

Gate valve Avalvethatisusedtoopenorcloseofftheflowoffluidthroughapipe.Itissonamedbecauseofthewedge(gate)thatiseitherraisedoutoforloweredintoadouble-seated sluice to permit full floworcompletely shut off flow. The passagewaythrough a gate valve is straight through,uninterrupted, and is the full size of thepipelineintowhichthevalveisinstalled.

Gland bushing Ametalbushinginstalledbetweenthepackingnutandthepackingtotransmittheforceexertedbythepackingnutagainstthepacking.

Globe valve Avalvethatisusedforthrot-tlingorregulatingtheflowthroughapipe.Itissonamedbecauseoftheglobularshapeofthebody.Thediscisraisedoffahorizon-talseatingsurfacetopermitfloworloweredagainstthehorizontalseatingsurfacetoshutoffflow.Thediscmaybeliftedcompletelytopermit full flowor liftedonlyslightly tothrottleorregulateflow.Theflowthroughaglobevalvehastomaketwo90°turns.

Hand wheel The wheel-shaped turningdevicebywhichthestemisrotated,thuslift-ingorloweringthediscorwedge.

Hinge pin Thevalvepartthatthediscorclapperofacheckvalveswings.

Outside screw and yoke A type ofbonnet so constructed that the operatingthreads of the stem are outside the valvehousing, where they may be easily lubri-catedanddonotcomeintocontactwiththefluidflowingthroughthevalve.

Packing A general term describing anyyieldingmaterialusedtoaffectatightjoint.Valvepackingisgenerally“jampacking”;itispushedintoastuffingboxandadjustedfromtimetotimebytighteningdownapackingglandorpackingnut.

Packing gland Adevicethatholdsandcompresses the packing and provides foradditional compression by manual adjust-ment of the gland aswear of the packingoccurs.Apackingglandmaybescrewedorboltedinplace.

Packing nut Anut that isscrewedintoplaceandpressesdownuponaglandbush-ing, which transmits the force exerted by



thepackingnuttothepacking.Itservesthesamepurposeasthepackinggland.

Rising stem Athreadedcomponentthatisunscrewedorscrewedthroughthebonnettoopenorclosethevalve.Thehandwheelmayrisewiththestem,orthestemmayrisethroughthehandwheel.

Screwed bonnet A type of bonnet soconstructed that it attaches to thebodybymeansofascrewedjoint.Abonnetmaybeattached to thebodybyscrewingover thebodyor insidethebody,orbymeansofauniontype,screwedconnection.

Solid wedge Awedgeconsistingofonesolid piece into which the valve stem isattached, so it seals against the valve seat-ingsurfacestoensureatightsealwhenthevalveisclosed.

Split wedge Awedge consistingof twopiecesintowhichthevalvestemisscrewed,so it expands the two pieces against thevalveseatingsurfacestoensureatightsealwhenthevalveisclosed.

Standard port The area through thevalveislessthantheareaofstandardpipe.

Stem Theusuallythreadedshafttowhichis attached thehandwheel at the topandthediscorwedgeatthelowerend.Thestemmayalsobecalledthe“spindle.”

Stop plug Anadjustingscrewthatextendsthroughthebodyofacheckvalve.Itadjustsandcontrolstheextentofmovementofthediscorclapper.

Swing check valve A check valve thatuses a hinged disc or clapper to limit thedirection of flow. The pressure exerted bythe fluid flowing through the valve forcesthe disc away from the seating surface.When the flow ceases, the clapper falls toitsoriginalposition,preventing flow in theoppositedirection.

Union A coupling fitting consisting ofthreeparts(ashoulderpiece,athreadpiece,andaring)thatisusedforcouplingtheendsof pipe sections. Adjoining faces of shoul-der and thread pieces are lapped togetherto form a tight joint. Unions permit easydisconnectionforrepairandreplacementofpipingandfittings.

Union bonnet A typeofbonnet that issoconstructedthatthewholebonnetassem-bly, including the hand wheel, stem, anddiscassembly,maybequicklyremovedbyunscrewingthebonnetunionringfromthevalvebody.

Union ring Alargenut-likecomponentthatsecurestheunionthreadandtheunionshoulder together. It slipsover andagainstthe shoulder piece and screws onto theunionthreadpiece.

Union shoulder piece A part of theunion fastened to thepipe that retains theunionring.

Union threaded piece Thatpartof theunion that is fastened to thepipe andhasexternal threadsoverwhichtheunionringisscrewedtoeffectacoupling.

Wedge (Seealsodisc.)Thewedge-shapeddevicethatfitsintotheseatingsurfacesofagatevalveandthatisdrawnoutofcontactwiththeseatingsurfacestopermitfloworispusheddownintocontactwith theseatingsurfacestocloseoffflowwiththevalve.

100% area (full port) Theareathroughthevalveisequaltoorgreaterthantheareaofstandardpipe.

MSS Standard Practices

NumberSP-25 Standard Marking System for Valves,

Fittings, Flanges and Unions

SP-42 150 lb. Corrosion Resistant Cast Flanged Valves

SP-67 Butterfly Valves

SP-70 Cast Iron Gate Valves, Flanged and Threaded Ends

SP-71 Cast Iron Swing Check Valves, Flanged and Threaded Ends

SP-72 Ball Valves with Flanged or Butt-Weld-ing Ends for General Service

SP-78 Cast Iron Plug Valves

SP-80 Bronze Gate, Globe, Angle and Check Valves

SP-81 Stainless Steel, Bonnetless, Flanged, Wafer, Knife Gate Valves

SP-82 Valve Pressure Testing Methods

SP-85 Cast Iron Valves

SP-110 Ball ValvesNotes: 1. Use of the last approved revi-

sion of all standards shall be used. 2. AlargenumberofformerMSSStandardPrac-ticeshavebeenapprovedby theAmericanNationalStandardsInstitute(ANSI)asANSIStandards. To maintain a single source ofauthoritativeinformation,MSSwithdrawsitsStandardPracticeswhentheyareapprovedasANSIStandards.

Valve Design Choices1. Multiturntype

A. GateB. Globe/angle-globeC. Endconnection

2. Checktype(backflowprevention)

A. SwingB. LiftC. SilentornonslamD. Endconnection

3. Quarter-turntype

A. BallB. Butterfly-resilientseatedC. PlugD. Endconnection.

Design Detail: Gate Valves

Advantages and Recommendations1. Goodchoiceforon-offservice

2. Fullflow,lowpressuredrop

3. Bidirectional

4. Bypassvalvesshouldbeprovidedwherethedifferentialpressureexceeds200psionvalves41/2to6in.and100psionvalves8in.andlarger.Bypassvalvesshouldbe1/2in.for4-in.valvesand¾in.for5-in.valvesorlarger.

Disadvantages1. Notforthrottling:Usefullyopenorfully

closed.Flowthroughapartiallyopengatevalvecausesvibrationandchat-teringandsubjectsthediscandseattoinordinatewear.

2. Metal-to-metalseatingmeansnotbestchoiceforfrequentoperation.Bubble-tightseatingshouldnotbeexpectedwithmetal-to-metaldesign.

3. Difficulttoautomate.

Disc and Seat Designs1. Bronzeorbronze-facedseatingsurfaces

areusedwithbronzeandironvalves.Ironvalvesmayuseall-ironseatingsurfaces.Thesearepreferredforlowpressuresandtemperaturesandforordinaryfluids.Stainlesssteelisusedforhigh-pressuresteamanderosivemedia.

2. Nonmetallic,“composition”discsareavailablefortightseatingorhard-to-holdfluids,suchasairandgasoline.

3. Solid-wedgediscdesignisthinneratthebottom,thickeratthetop,andforcedintotheseatofasimilarshape.

4. Double-discorsplit-wedgediscdesignaretwodiscsemployedbacktobackwithaspreadingdevicebetweenthem.Asthevalvewheelisturned,thegatedropsintoitsseat(aswithanyothergatevalve),butonthefinalturnsofthewheel,thespreaderforcesthediscsout-wardagainsttheseats,effectingtighterclosure.

5. Resilientwedgeisarubberencapsu-latedmetalwedgethatsealsagainstanepoxy-coatedbody.Resilientwedgeislimitedtocold-waterapplications.

Design Detail: Globe/Angle-Globe Valve

Advantages and Recommendations1. Recommendedforthrottlingapplica-

tions.

2. Positivebubble-tightshut-offwhenequippedwithresilientseating.

3. Goodforfrequentoperation.

4. Easytorepair.




Disadvantages1. Flowpathcausesasignificantpressure

drop.

2. Globevalvesaremorecostlythanalter-nativevalves.

Disc and Seat Designs1. Resilient(soft)seatdiscsarepreferred

overmetal-to-metalexceptwheretem-peratures,veryclosethrottlingorabra-siveflowmakeall-metalseatingabetterchoice.Stainlesssteeltrimisavailableformedium-tohigh-pressuresteamandabrasiveapplications.Tetrafluoroethyl-ene(TFE)isthebestresilientdiscmate-rialformostservices,althoughrubber’ssoftnessgivesgoodperformanceincoldwater.TFEisgoodupto400°F.Butadi-eneandacrylonitrile(Buna-N)isgoodupto200°F.

2. Automatic,steam,stop-check,angle-globevalvesarebestonmedium-pres-suresteamservice.

3. Wheretheslidingactionofthesemiplugdiscassemblypermitsthevalvetoserveasashut-offvalve,throttlingvalve,andoracheckvalve.

Design Detail: Check Valves (Backflow Prevention)1. Swingtypecheckvalvesoffertheleast

pressuredropandoffersimpleauto-maticclosure;whenfluidflowstops,gravityandflowreversalclosethevalve.ManybronzevalvesofferaY-patternbodywithanangleseatforimprovedperformance.ResilientTeflonseatingispreferredfortightershut-off.

2. Liftcheckscomeinanin-lineorglobe-stylebodypattern.Bothcausegreaterpressuredropthantheswingtype,withthehorizontalpatternsimilarinrestric-tiontoglobevalves.

3. Somestylesarespringactuatedandcenterguidedforimmediateclosurewhenflowstops.Thein-line,spring-actuatedliftcheckisalsoreferredtoasthe“silentcheck”becausethespringclosesthevalvebeforegravityandfluidreversalcanslamthevalveclosed.Resil-ientseatingisrecommended.

4. Double-disccheckvalveshavetwindiscsonaspring-loadedcentershaft.Thesevalveshavebetterflowcharac-teristicsthanliftchecksandmostoftenuseawaferbodyforlowcostandeasyinstallation.Resilientseatingisrecom-mended.

Design Detail: Quarter-Turn Ball Valves

Advantages and Recommendations1. Bubble-tightshut-offfromresilient(TFE)

seats

2. Quick,90°open/close,nottorquedependentforseating

3. Straight-through,unobstructedflow,bidirectional

4. Easiertoautomatethanmultiturnvalves

5. Morecompactthanmultiturnvalves

6. Offerlongcyclelife.

Disadvantages1. Temperatureandpressurerangelimited

byseatmaterial.

2. Cavityaroundballtrapsmediaanddoesnotdrainentrappedmedia.Susceptibletofreezing,expansion,andincreasedpressureduetoincreasedtemperature.

Body Styles1. One-piecevalveshavenopotential

bodyleakpathbuthaveadoublereducedport,thus,significantpressuredropoccurs.Notrepairable,theyareusedprimarilybychemicalandrefiningplants.

2. Two-pieceendentriesareusedmostcommonlyinbuildingservices.Theyarethebestvaluevalvesandareavailableinfull-orstandard-portballs.Theyarerecommendedforon-offorthrottlingserviceandnotrecommendedtoberepaired.

3. Three-piecetypevalvesaremorecostlybutareeasiertodisassembleandofferthepossibilityofin-linerepair.Theyareavailableinfull-orstandard-portballs.

Port Size1. Full-portballvalvesprovideapressure

dropequaltotheequivalentlengthofthepipe,slightlybetterthangatevalves.

2. Standard-(conventional-)portballsareuptoonepipesizesmallerthanthenominalpipesizebutstillhavesignifi-cantlybetterflowcharacteristicsthanglobevalves.

3. Reduced-portballvalveshavegreaterthanonepipesizeflowrestrictionandarenotrecommendedinbuildingservicespipingbutratherareusedforprocesspipingforhazardousmaterialtransfer.

End Connections1. ThreadedballvalveswithANSIfemale

taperthreadsaremostcommonlyusedwithpipeupto2in.

2. Soldered-endvalvespermitthedirectconnectionofbronzeballvalvesto2-

in.coppertubing.Caremustbetakennottooverheatanddamagethevalvesduringthesolderingprocess.

Handle Extensions1. Insulatedhandleextensionsorextended

handlesshouldbeusedtokeepinsu-latedpipingsystemsintact.

Design Detail: Quarter-Turn Butterfly Valves

Advantages and Recommendations1. Bubble-tightshut-offfromresilientseats

2. Quick,90°open/close;easiertoauto-matethanmultiturnvalves

3. Verycost-effectivecomparedtoalterna-tivevalvechoices

4. Broadselectionoftrimmaterialstomatchdifferentfluidconditions

5. Morecompactthanmultiturnvalves

6. Offerlongcyclelife

7. Dead-endservice.

Disadvantages1. Nottobeusedwithsteam.

2. Gearoperatorsareneededfor8in.andlargervalvestoaidinoperationandprotectagainstoperatingtooquicklyandcausingdestructivelineshock.

Body Styles1. Waferstylevalvesareheldinplace

betweentwopipeflanges. Theyareeasytoinstallbutcannotbeusedasisolationvalves.

2. Lug-stylevalveshavewaferbodiesbuttappedlugsmatchinguptoboltcirclesofclass125/150-lbflanges.Theyareeasilyinstalledwithcapscrewsfromeitherside.Lugstyledesignsfromsomemanufacturerspermitdroppingthepipefromonesidewhilethevalveholdsfullpressureifneeded.

3. Groovebutterflyvalvesdirectlyconnecttopipeusingiron-pipe-size,groovedcouplings.Whilemorecostlythanwafervalves,groovedvalvesaretheeasiesttoinstall.

Design Detail: Quarter-Turn Valves, Lubricated Plug Cocks

Advantages and Recommendations1. Bubble-tightshut-offfromstemsealof

reinforcedTeflon.Leakproof,spring-loadedballandlubricated,sealedcheckvalveandcombinationlubricantscrewandbuttonheadfittingpreventforeignmatterfrombeingforcedintothelubri-cationsystem.

2. Quick,90°open/close,notdependentontorqueforseating.



3. Straight-through,unobstructedflow,bidirectionalflow,three-wayflow,orfour-wayflow.

4. Offerslongcyclelife.

5. Adjustablestopforbalancingorthrot-tlingservice.

6. Canbesuppliedwithround,diamond,orrectangular(standard)plug.

7. Mechanismforpoweroperationorremotecontrolofanysizeandtypetooperatewithair,oil,orwater.

Disadvantages1. Temperatureandpressurerangelimited

bytypeoflubricantsealantandANSIStandardrating,i.e.150psisteamwork-ingpressure(SWP)and200psinon-shock,coldworkingpressure(CWP),andwater,oil,gas(WOG).

General Valve Specification by Service

Hot and Cold Domestic Water Service

Gate valve2 in. and smaller Valves2in.andsmallershall be class 125, rated 125 psi SWP, 200psinonshockCWP,risingstem.Body,unionbonnet,andsolidwedgeshallbeofASTMB-62castbronzewiththreadedends.Stemsshall be of dezincification-resistant siliconbronze,ASTMB-371,orlow-zincalloy,ASTMB-99. Packing glands shall be of bronze,ASTM B-62, with aramid fiber, nonasbes-tospacking,completewithmalleablehandwheel.ValvesshallcomplywithMSSSP-80.

2½ in. and larger Valves 21/2 in. andlargershallbeclass125,rated100psiSWP,150 psi nonshock CWP; and have an ironbody, bronze-mounted outside screw andyoke(OS&Y),withbodyandboltedbonnetconformingtoASTMA-126classBcast-iron,flangedends,witharamidfiber,nonasbestospackingandtwo-piecepackingglandassem-bly.ValvesshallcomplywithMSSSP-70.

Alldomesticwatervalves4in.andlargerthatareburied in thegroundshallbe ironbody, bronze-fitted, with O-ring stem seal;andhaveepoxycoatinginsideandoutsideand a resilient-seatedgate valvewithnon-risingstemandmechanicaljointorflangedendsas required.Allvalves furnishedshallopen left.All internalparts shall be acces-siblewithoutremovingthevalvebodyfromthe line. Valves shall conform to AWWAC509-89, Standard for Resilient-Seated Gate Valves. Epoxy coating shall conformto AWWA C550-90, Standard for Protective Epoxy Interior Coating for Valves.

Ball valves2 in. and smaller Valves2in.andsmallershallberated150psiSWP,600psinonshockCWP;andhavetwo-piece,castbrassbodies,replaceablereinforcedTeflonseats,full-port

¼–1 in., conventional-port 1¼–2 in., blow-out-proof stems, chrome-plated brass ball,andthreadedorsolderedends.ValvesshallcomplywithMSSSP-110

Globe valves2 in. and smaller Valves2in.andsmallershallbeofclass125,rated125psiSWP,200psinonshockCWP;bodyandbonnetshallbe of ASTM B-62 cast-bronze compositionwiththreadedorsolderedends.Stemsshallbeofdezincification-resistantsiliconbronze,ASTMB-371,orlow-zincalloy,ASTMB-99.Packingglandsshallbeofbronze,ASTMB-62,witharamidfiber,nonasbestospacking,completewithmalleablehandwheel.ValvesshallcomplywithMSSSP-80.

2½ in. and larger Valves 21/2 in. andlargershallbeclass125,rated125psiSWP,200 psi nonshock CWP; and have an ironbody, bronze-mounted OS&Y, with bodyand bolted bonnet conforming to ASTMA-126 classB cast-iron, flanged ends,witharamidfiber,nonasbestospacking,andtwo-piecepackinggland assembly.Valves shallcomplywithMSSSP-85.

Butterfly valves2½ in. and larger Valves 21/2 in. and

largershallberated200psinonshockCWP;and have a lug or IPS grooved type bodywith2-in.extendedneckforinsulating.Theyshallbeductileiron,ASTMA536;withstain-lesssteeldisc;416stainlesssteelstem;eth-ylene-propylenedienemonomer(EPDM)O-ringstemseals;andresilient,EPDMrubbermolded to seat. Sizes 21/2 to 6 in. shall belever operated with a ten-position throt-tlingplate;sizes8to12in.shallhavegearoperators;sizes14in.andlargershallhavewormgearoperatorsonly.Theyaresuitableforuseasbidirectionalisolationvalvesand,as recommended by the manufacturer, ondead-endserviceatfullpressurewithouttheneedfordownstreamflanges.

ValvesshallcomplywithMSSSP-67.Note: Butterfly valves in dead-end ser-

vicerequirebothupstreamanddownstreamflanges for proper shut-off and retentionor must be certified by the manufacturerfor dead-end service without downstreamflanges.

Check valves2 in. and smaller Valves2in.andsmallershallbeclass125,rated125psiSWP,200psinonshockCWP; andhave threadedor sol-deredends,withbodyandcapconformingto ASTMB-62 cast bronze composition, y-patternswingtypedisc.ValvesshallcomplywithMSSSP-80

Note: Class150valvesmeetingtheabovespecifications may be used where systempressure requires. For class 125 seat disc,specifyBuna-NforWOGserviceandTFEfor

steamservice.Forclass150seatdisc,specifyTFEforsteamservice.

2½ in. and larger Valves 21/2 in. andlargershallbeclass125,rated125psiSWP,200psi nonshockCWP; ironbody, bronzemounted,withbodyandboltedbonnetcon-forming to ASTM A-126 class B cast-iron,flanged ends, swing type disc, and nonas-bestosgasket.ValvesshallcomplywithMSSSP-71.

Alternative check valves (21/2 in. andlarger) shall be class 125/250 iron body,bronze mounted, wafer check valve, withendsdesignedforflangedtypeconnection,aluminum bronze disc, EPDM seats, 316stainlesssteeltorsionspring,andhingepin.

A spring-actuated check valve is to beusedonpumpdischarge.Swingcheckwithoutsideleverandspring(notcenterguided)is tobeusedonsewageejectorsorstorm-watersumppumps.

Fire-Protection System

Gate valves2 in. and smaller Valves 2 in. and

smallershallbeofclass175psiwaterwork-ing pressure (WWP) or greater, with bodyandbonnetconformingtoASTM-B-62,cast-bronzecomposition, threadedends,OS&Y,solid disc and listed by UL, FM approved,andincompliancewithMSSSP-80.

2½ in. and larger Valves 21/2 in. andlargershallberated175psiWWPorgreater,andhaveanironbody,bronzemountedorwith resilient rubber encapsulated wedge,withbodyandbonnetconformingtoASTMA-126, class B cast-iron, OS&Y, class 125flanged or grooved ends. If of resilientwedgedesign,interiorofvalveistobeepoxycoated.ValvesshallmeetorexceedAWWAC509-89,Standard for Protective Epoxy Inte-rior Coating for Valves.ValvesaretobeULlisted,FMapproved,andincompliancewithMSSSP-70.

Valves 4 in. and larger for under-ground buryshallberated200psiWWPor greater, with body and bonnet con-forming to ASTM A-126, class B cast iron,bronzemounted,resilient-seatedgatevalvewithnonrisingstem,withO-ringstemseal,epoxycoatinginsideandoutside,flangedormechanicaljointendsasrequired.Allvalvesfurnished shall open left. All internal partsshall be accessible without removing thevalvebodyfromthe line.Valvesshallcon-formtoAWWAC509-89,Standard for Resil-ient-Seated Gate Valves. Epoxycoatingshallconform to AWWA C550-90, Standard for Protective Epoxy Interior Coating for Valves.ValvesshallcomecompletewithmountingplateforindicatorpostandbeULlisted,FMapproved,andincompliancewithMSSSP-70.




When required, a vertical indicator post may be used on underground valves. Posts must provide a means of knowing if the valve is open or shut. Indicator posts must be UL listed and FM approved.

High-Rise Service

Gate valves2½- to 12-in. Gate valves 2½ to 10 in. shall be rated 300 psi WWP or greater, 12 in. shall be rated 250 psi WWP, and have an iron body, bronze mounted, with body and bonnet conforming to ASTM A-126, class B, cast iron, OS & Y, with flanged ends for use with class 250/300 flanges. They shall be UL listed, FM approved, and in compliance with MSS SP-70.

Check valves2½- to 12-in. Check valves 2½ to 10 in. shall be rated 300 psi WWP or greater, 12 in. shall be rated 250 psi WWP, and have an iron body, bronze mounted, with a horizontal swing check design, with body and bonnet conforming to ASTM A 126 Class B, cast

iron, with flanged ends for use with class 250/300 flanges. They shall be UL listed, FM approved, and in compliance with MSS SP-71.

Note: In New York City, valves are to be approved by the New York City Materials and Equipment Acceptance Division (MEA), in addition to the above specifications.

Ball valves2 in. and smaller Valves 2 in. and smaller shall be constructed of commercial bronze, ASTM B 584, rated 175 psi WWP or higher, with reinforced TFE seats. Valves shall have a gear operator with a raised position indi-cator and two internal supervisory switches. Valves shall have threaded or IPS grooved ends and shall have blowout-proof stems and chrome-plated balls. They shall be UL listed, FM approved, and in compliance with MSS SP-110 for fire-protection service.

Butterfly valves4 to 12 in. Butterfly valves may be sub-stituted for gate valves, where appropri-ate. Valves shall be rated for 250 psi WWP,

175 psig working pressure, UL listed, FM approved and in compliance with MSS SP-67.

Valves furnished shall have ductile-iron ASTM A-536 body, and may have ductile-iron ASTM A-395 (nickel-plated) discs or alumi-num bronze discs, depending upon the local water conditions. In addition, wafer style for installation between class 125/150 flanges or lug style or grooved body may be specified, depending upon the system needs.

Valves shall be equipped with weather-proof gear operator rated for indoor/out-door use, with hand wheel and raised posi-tion indicator with two internal supervisory switches.

Check valves Valves 2½ in. and larger shall be 500 psi WWP, bolted bonnet, with body and bonnet conforming to ASTM A-126, class B cast iron, flanged end with com-position y-pattern, horizontal, swing type disc. They shall be UL listed, FM approved, and in compliance with MSS SP-71 type 1 for fire-protection service. n




1. Dezincification occurs in valves as a result of _________.a. electrolysisb. high velocityc. high pressured. water hammer

2. All domestic water gate valves 4 inches and larger that are buried in the ground shall be iron body, bronze fitted with __________.a. o-ring stem sealb. epoxy coating inside and outc. resilient seatsd. all of the above

. MSS withdraws its standard practices when __________.a. they have been revisedb. they are approved as ANSI standardsc. they are in conflict with local codesd. none of the above

4. The valve type that is best suited for all services is a __________ valve.a. ball b. gatec. globed. none of the above

. When a gate valve is fully open, it __________.a. has the highest resistance to flow of all valve typesb. has the least resistance to flow of all valve typesc. causes water hammer in the piping systemd. creates velocity surges

6. Butterfly valves in dead-end service require __________.a. flanges upstream and down stream for shut-off and

proper retentionb. lock nuts on the flange boltsc. certification by the manufacture for dead-end service

without downstream flangesd. a or c but not b

. Bypass valves should be provided where the differential pressure exceeds __________ psi on valves sized 4-6 inches.a. 100b. 150c. 200d. 250

8. Two-inch and smaller ball valves rated 10 psi SWP, 600 psi non-shock CPW with two-piece, cast brass bodies, replaceable reinforced Teflon seats, blowout-proof stems, chrome plated brass ball and threaded or soldered ends must comply with MSS __________.a. SP-110b. standard practicesc. SP-72d. all of the above

. The cap of a check valve is the equivalent to the ______.a. bonnet of a gate or globe valveb. operating pressurec. packing gland of a ball valved. none of the above

10. By-pass valves __________.a. are required when differential pressure exceeds 200

psi on gate valves 4-6 inches and 100 psi gate valves 8 inches and larger

b. must be 2 inches in diameterc. should be provided where the differential pressure

exceeds 200 psi on gate valves 4½-6 inches and 100 psi on gate valves 8 inches and larger

d. must be ½ inch or ¾ inch only

11. One advantage of the butterfly valve is that it can be placed in very small spaces between __________.a. other valvesb. equipmentc. pipingd. pipe flanges

12. When flow begins in a globe valve, __________.a. wire drawing is minimizedb. contact between the seat and disk endsc. a and b aboved. none of the above

Do you find it difficult to obtain continuing education units (CEUs)? Is it hard for you to attend technical seminars? Through Plumbing Systems & Design (PS&D), ASPE can help you accumulate the CEUs required for maintaining your Certified in Plumbing Design (CPD) status.

ASPE features a technical article in every issue of PS&D, excerpted from its own publications. Each article is followed by a multiple-choice test and a simple reporting form.

Reading the article and completing the form will allow you to apply to ASPE for CEU credit. For most people, this process will require approximately 1 hour. A nominal processing fee is charged—$25 for ASPE members and $35 for nonmembers (until further notice, the member fee is waived). If you earn a grade of 90% or higher on the test, you will be notified that you have logged

0.1 CEU, which can be applied toward the CPD renewal requirement or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for 3 years.

No certificates will be issued in addition to the notification letter. You can apply for CEU credit on any technical article that has appeared in PS&D within the past 12 months. However, CEU credit only can be obtained on a total of eight PS&D articles in a 12-month period.

Note: In determining your answers to the CE questions, use only the material presented in the continuing education article. Using other information may result in a wrong answer.

Continuing Education from Plumbing Systems & DesignKenneth G.Wentink, PE, CPD, and Robert D. Jackson, Chicago Chapter President

CE Questions—“Valves” (PSD 130)



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PSD

137

VentSystems



PSDMAGAZINE.ORG


Flow of air is the primary consideration in the design of a venting system for the ventilation of the piping and protection of the fixture trap seals of a sanitary drainage system. Since air is of such primary importance, it is essential that the plumbing engineer be familiar with certain physical characteristics that are pertinent to its behavior in a plumbing system.

Density of any substance is its mass per unit volume. The den-sity of air is its weight in pounds per cubic foot of volume. The density of air is affected by temperature, moisture content, and pressure. The density of “standard air” is taken at atmospheric pressure and 68.4°F. It is equal to 0.075 lbm/ft3. With a rise in temperature, the density of air decreases and with a lowering of temperature its density increases. The moisture content of air in the plumbing system has a negligible effect on its density and can be disregarded in all calculations. Pressure has an appre-ciable effect; the higher the pressure the greater the density, and the lower the pressure the less the density.

Specific Weight of a fluid is not an absolute property, but depends upon the local gravitational field (gravitational accel-eration on earth is g=32.2 ft/sec2) and the properties of the fluid itself. Commonly called “density” when concerning gravita-tional force, the numerical value of specific weight (lbf/ft3) is equal to density (lbm/ft3).

Elasticity is the ability of a substance to assume its original characteristics after the removal of a force that has been applied. Air is a perfectly elastic substance. From the scientific definition of elasticity it becomes clear that a rubber band is really a very inelastic material. If a weight is suspended from a rubber band and left for a few hours, then the weight is removed, the rubber band will spring back, but definitely not to its original length. If a force is applied to air, the force can be applied for days or years, and when it is removed, the air will return exactly to its original condition.

Air is compressible. There is an increase in pressure when air is compressed. In the plumbing system, only an extremely small change in pressure can be tolerated. For a pressure of 1 in. of water column (0.036 psi), the volume of air will be compressed by 1∕400 of its original volume. Assuming an original volume of 400 ft3 of air at atmospheric pressure and the application of a pressure of 1 in. of water column, the air will be compressed by 400 × 1∕400 = 1 ft3. It is obvious that a comparatively small change in volume can very easily cause the accepted design limitation of ±1 in. of pressure to be exceeded with the consequent danger of destroying the trap seals. The vent piping must be designed to permit the air to flow freely without compression or expansion except for the small amount necessary to overcome friction.

Static HeadStatic head is the pressure exerted at any point by the weight of the substance above that point. The pressure can be stated in feet of the substance, i.e., when the substance is water the static head is 100 ft of water, or if the substance is air, 100 ft of air. To convert from feet of head to pounds-force per square inch:

(1)p = γh and h = 144p

144 γwhere p = Pressure, lbf./in2

γ = Specific weight of substance, lbf/ft3

h = Static head, ft

Pneumatic effectS in Sanitary SyStemSAs water flows in contact with air in vertical or horizontal piping, there is friction between the air and water. The frictional effect causes the air to be dragged along with the water and at practi-cally the same velocity as the water. When the cross-sectional area of the water occupying the pipe is suddenly increased, such as at the hydraulic jump or where a branch discharges into the stack, the air passage is constricted. This constriction acts exactly the same as a stoppage or a blockage to the flow of air. This causes a buildup of pressure, the highest pressure occur-ring at the constriction and diminishing upstream. It is for this reason that excessive pressure usually develops at the lower floors of a building and at offsets of the stack. It is important to always be aware that protection from the entry of sewer gases is afforded by the 2-in. trap seal, and the design of plumbing sys-tems must be such as to maintain pressure variations within ±1 in. column of water.

rate of flow from outletSThe velocity at which air flows out of an outlet to the atmosphere (at the roof terminal of a stack) is due to the total pressure avail-able in the vent pipe at the outlet. This pressure is the flow pres-sure, which is equal to the static pressure less the pressure lost in friction. The maximum rate of discharge in practice is expressed as:

(2)qD = cD q1

where qD = Actual quantity of discharge, gpm q1 = Ideal quantity of discharge, gpm cD = Coefficient of dischargeUtilizing the formula q = AV and substituting,

(3)qD = cD (2.448 dO

2 V1)where dO = Outlet diameter, in. V1 = Ideal velocity, fps

Velocity is equal to √2gh, where g = acceleration due to gravity and h = height (or head) of air column.

(4)qD = cD (2.448 dO

2 √2gh)(5)

= cD (19.65 dO2 √h)

Using 0.67 as an acceptable coefficient of discharge, per Equation 6-1,

Vent Systems

Reprinted from Engineered Plumbing Design II, Chapter 8: “Vent Systems,” by A. Calvin Laws, PE, CPD.© American Society of Plumbing Engineers.

Plumbing Systems & Design JANUARY/FEBRUARY 2007 PSDMAGAZINE.ORG



qD = 13.17 dO2 h½

Static PreSSure of airThe design criterion of maintaining pneumatic pressure fluctuations within ± l in. of water column is constantly stressed throughout this book. It should prove interesting to state this pressure in terms of an equivalent column of air. The formula for any substance is, per Equation 1:

P =γ h144

then

(6)

P =γW hW =

γA hA

144 144where γW = Specific weight of water, lbf/ft3

hW = Static head of water, ft γA = Specific weight of air, lbf/ft3

hA = Static head of air, ft

Transposing and using 1 in. of water column,

hA =γW hW = (62.408) (1⁄12)γA 0.07512 (at 70° F.)

hA = 69.23 ft of air column

A column of air 69.23 ft will exert the same pressure as a column of water 1 in. high. Stated another way, a static head of 1 in. of water will support a column of air 69.23 ft high.

The rate of discharge from a vent outlet can now be determined when the pressure at the outlet is 1 in. of water or 69.23 ft of air.

qD = 13.17 dO2 h½

= 13.17 dO2 (69.23)½

= (13.17) (8.32) dO2

= 109.57 dO2

The gallons per minute (cubic feet per minute) discharge rate for various diameters of vent pipe at a flow pressure of 1 in. of water column is given in Table 1.

friction Head loSSWhen air flows in a pipe there is a pressure loss which occurs due to the friction between the air and pipe wall. This loss of pressure can be expressed by the Darcy formula:

(7)

h = f L V2

D2 gwhere h = friction head loss, ft. of air column f = coefficient of friction L = length of pipe, ft. D = diameter of pipe, ft. V = velocity of air, ft/sec g = gravitational acceleration 32.2 ft./sec2

air flow in StackSThe complete venting of a sanitary drainage system is very complicated as evidenced by the variety of vents employed. There are so many variables that produce positive and negative

pneumatic pressure fluctuations that it is not feasible to prepare tables of vent sizing for each particular design. Recognizing this, authorities base the formulation of venting tables for vent stacks and horizontal branches on the worst conditions that may rea-sonably be expected. To determine the maximum lengths and minimum diameters for vent stacks it would be valuable to review the conditions of flow in the drainage stack.At maximum design flow, the water flows down the stack as a sheet of water occupying 7∕24 of the cross-sectional area of the stack. The remaining 17∕24 is occupied by a core of air. As the water falls down the stack, it exerts a frictional drag on the core of air and as this air is dragged down it must be replaced by an equivalent quantity of air so as not to develop negative pressures in excess of -1 in. of water. This is accomplished by extending the soil stack through the roof so that air may enter the stack to replenish the air being pulled down the stack. This is why stacks must be extended full size through the roof and also why soil stacks may not be reduced in size even though the load is less on the upper portions of the stack than it is at the lower portions. Any restriction in the size before terminating at the atmosphere would cause violent pressure fluctuations.

As the water flows down the stack and enters the horizontal drain there is a severe restriction to the flow of air as the hydrau-lic jump occurs. The air is compressed and pressure buildup may become very high. A vent stack is provided in this area of high pressure to relieve the pressure by providing an avenue for the flow of air. Obviously, the vent stack must be large enough to permit the maximum quantity of air dragged down the drain-age stack to discharge through it and to the atmosphere without exceeding ±1 in. of water fluctuation The rate of air discharge that must be accommodated for various sizes of drainage stacks flowing at design capacity is tabulated in Table 2.

air flow in Horizontal drainSIt is assumed that the drainage branch flows half full at design conditions and the air in the upper half of the pipe is flowing at the same velocity and capacity. Table 3 tabulates these values for various slopes of drain.

Table 2 Air Required by Attendant Vent Stacks (Drainage Stack Flowing 7∕24 Full)

Diameter of Drainage Stack, inches Water Flow, gpm Air Flow, gpm (cfm)

2 23.5 57.1 (7.6)3 70.0 170.1 (22.7)4 145.0 352.4 (47.1)5 270.0 656.1 (87.7)6 435.0 1057.1 (141.3)8 920.0 2235.6 (298.9)

10 1650.0 4009.5 (536)12 2650.0 6439.5 (860.8)

Table 1 Discharge Rates of Air (1 Inch Water Pressure)

Outlet Diam, dO inches

Air Discharge, qD gpm (cfm)

2 438.3 (58.6)2½ 684.8 (91.5)3 986.1 (131.8)4 1753.0 (234.3)5 2739.0 (366.1)

Table 3 Rate of Air In Horizontal DrainsDiameter of Drain,

inchesSlope,

inches per foot

Rate of Flow,

gpm (cfm)1½ ¼ 6.0 (.80)2 ¼ 8.8 (1.2)2½ ¼ 15.5 (2.1)3 ¼ 25.5 (3.4)4 1⁄8 38.0 (5.1)5 1⁄8 69.0 (9.2)6 1⁄8 112.0 (15)8 1⁄8 240.0 (32.1)

JANUARY/FEBRUARY 2007 Plumbing Systems & Design


PermiSSible lengtH of Vent PiPeThe maximum length of vent piping, for any particu-lar size with a pressure drop of 1 in. of water, is estab-lished by computing the pressure loss for various rates of flow in vents of various diameters. Combining Dar-cy’s pipe friction formula (Equation 7) and the flow formula, and converting the terms of the equations to units generally used in plumbing:

h = f L V2

D 2g(8)

q = 2.448 d2V(9)

V = q

2.448d2

Substituting V in the Darcy equation,

h = f Lq2

(d⁄12)(64.4)(2.448)2(d)4

Solving for L,(10)

L = h d5= 2226 d5

0.013109 f q2 f q2

where L = Length of pipe, ft d = Diameter of pipe, in. f = Coefficient of friction q = Quantity rate of flow, gpm

graVity circulationThe principle of gravity circulation of air is utilized to keep the entire sanitary system free of foul odors and the growth of slime and fungi. The circulation is induced by the difference in head (pressure) between outdoor air and the air in the vent piping. This differ-ence of head is due to the difference in temperature, and thus the difference in density, of each and the height of the air column in the vent piping. The cool air, being more dense, tends to displace the less dense air of the system and circulation of the air is induced. The formula is

(11)H = 0.1925 (γO - γ1) HS

where H = Natural draft pressure, in. of water γO = Specific weight of outside air, lbf/ft3

γ1 = Specific weight of air in pipe, lbf/ft3

HS = Height of air column or stack, ft

Under conditions of natural draft, the rate of flow will be just great enough to overcome losses due to friction.

Vent StackSEvery drainage stack should be extended full size through the roof. The pipe from the topmost drainage branch connection through the roof to atmosphere is called the “vent extension.” The vent extension provides the air that is dragged down the stack and also provides means for the gravity circulation of air throughout the system. Vent extensions may be connected with the vent stack before extending through the roof or may be con-nected together with other vent extensions or vent stacks in a vent header and the header extended through the roof as a single pipe.

Every drainage stack should have an attendant vent stack. The purpose of installing a vent stack is to prevent the development of excessive pressures in the lower regions of the drainage stack by relieving the air as rapidly as it is carried down by the dis-charge of the drainage stack. The most effective location for the vent stack is below all drainage branch connections and pref-erably at the top of the horizontal drain immediately adjacent to the stack base fitting. It is at this location that pressure is at its maximum and the danger of closure due to fouling is at its minimum. Figure 1 illustrates acceptable methods of vent stack connections.

The vent stack should extend undiminished in size through the roof or connect with the vent extension of the drainage stack at least 6 in. above the overflow of the highest fixture or connect to a vent header.

Vent terminalSVent terminals should not be located within 10 ft of any door, window, or ventilation intake unless they are extended at least 2 ft above such openings. Terminals should be at least 6 in. above roof level and at least 5 ft above when the roof is used for other

Figure 1 Various Vent Stack Connections


CONTINUING EDUCATION: Vent Systems


purposes. When it is impractical to extend the vent through the roof, it is permissible to terminate through a wall, but the ter-minal must turn down and be covered with a wire screen. The terminal should never be located beneath a building overhang.

fixture traP VentSThe water seal of all fixture traps should be protected against siphonage or blowout by the proper installation of a venting system. When drainage stacks are provided with an adequate supply of air at the terminal and an adequate vent stack is pro-vided to relieve excess pressures at the base of the drainage stack, the only additional vent protection required to prevent water seal loss in fixture traps is that necessary to prevent self-si-phonage when the fixture discharges and to relieve excessive pneumatic effects in the branch drains when other fixtures dis-charge into the branch. Some municipalities require that every fixture trap be individually vented, but most localities permit alternate methods such as

1. Wet venting2. Stack venting3. Circuit and loop venting4. Combination waste and vent venting

diStance of Vent from traPThe most comprehensive investigations of conditions under which fixture traps will be safe from self-siphonage have been conducted by the National Bureau of Standards in the United States and by the Building Research Station in England. The rec-ommended maximum distances of a vent from the weir of the trap to the vent connection are tabulated in Table 4.

As illustrated in Figure 2, the vent pipe opening, except for water closets and similar fixtures, must never be below the weir of the fixture trap. A fixture drain that slopes more than one pipe diam-eter between vent opening and trap weir has a greater tendency to self-siphon the trap seal than a fixture drain installed at a slope of not more than one pipe diameter.

Self-Siphonage of Fix-ture Traps, National Bureau of Standards Building Materials and Structures Report BMS 126 (1951), prepared by John L. French and Herbert N. Eaton, is a very thorough study of self-siphonage

Some of the conclusions drawn by French and Eaton as a result of their investigations are very illuminating and are quoted herewith:

1. Increasing the diameter of the outlet orifice of a lavatory from 11⁄8 in. to 1¼ in. increases the trap seal loss greatly, fre-quently more than 100%, owing to the increased discharge rate.

2. Flat-bottomed fixtures cause smaller trap seal losses than do round fixtures, owing to the greater trail discharge from the former.

3. With a 1½-in. fixture trap and drain, an 1in. by 20-in. lava-tory gave greater trap-seal losses than did a 20-in. by 24-in. lavatory, presumably owing to the greater trail discharge of the latter. When a 1¼ in. trap and drain were used, no par-ticular difference was noted in the trap seal losses caused by the two lavatories.

4. The elimination of the overflow in lavatories will increase the trap seal losses substantially.

5. The effect on trap seal losses of varying the vertical distance from the fixture to the trap from 6 in. to 12 in. appears to be negligible.

6. For a given rate of discharge from a lavatory, decreasing the diameter of the drain will increase trap seal losses.

7. An increase in slope or a decrease in diameter of the fixture drain will tend to cause increased losses due to self-siphon-age, and these two dimensions are fully as important as the length of fixture drain in causing self-siphonage.

8. Trap seal losses are usually much greater when a long-turn stack fitting is used than when a short-turn or straight-tee fitting is used. No significant difference between the behav-ior of short-turn and straight-tee fittings was observed. Thus, since it is known that a long-turn fitting is more effec-tive in introducing water from a horizontal branch into the stack than is either the short-turn or straight-tee fitting, the characteristics of these fittings are contradictory in these respects. The fitting that is most advantageous from the standpoint of introducing the water into the stack is the least advantageous from the standpoint of self-siphonage.

9. Trap seal losses are increased if the internal diameter of a P-trap is less than that of the fixture drain. Thus, if we are to prevent excessive trap seal losses for a P-trap due to self-siphonage, we should use a trap having a fairly large internal diameter. Furthermore, siphonage of the trap due to pressure reductions caused by the discharge of other fix-tures on the system can be rendered less harmful by using a trap with a large depth of seal. While increasing the depth of seal may lead to greater trap seal losses, it also results in a greater remaining trap seal than if a trap with a shallow seal were used.

10. The test results on the self-siphonage of water closets have indicated that the unvented length of drain for these fixtures need not be limited because of self-siphonage.

11. Standardization of the dimensions of fixture traps and especially of lavatory traps, with regard to internal diameter and depth of trap seal is highly desirable. Minor restrictions on these dimensions can lead to substantially increased lengths of fixture drains.

Figure 2 Vent Pipe Opening

Table 4 Distance of Vent from Fixture Traps

Size of Fixture Drain inches

Maximum Distance of Vent to Trap

inches1¼ 301½ 422 603 724 120



12. Standardization of the hydraulic characteristics of fixtures is desirable, at least for lavatories, sinks, and combination fix-tures. Substantially increased permissible unvented lengths of fixture drains can be obtained for a moderate decrease in the discharge rates of the fixtures.

13. Increase in depth of trap seal above the 2-in. minimum commonly permitted by codes will make it possible to increase appreciably the maximum permissible unvented lengths of fixture drains.

These conclusions clearly illustrate various approaches in the effort to make plumbing systems less costly without affecting efficiency. The proper design of fixtures and fixture drain lines and limiting the maximum discharge rates of faucet-controlled fixtures could result in longer unvented lengths of drains.

VariouS metHodS of fixture traP VentingFigure 3 illustrates various fixture trap vents and their proper nomenclature. When venting one trap the vent is called an “indi-vidual” or “back vent.” If fixtures are back to back or side by side and one vent is used for the two traps, the vent is a “common vent.” Any connection from the vent stack is a “branch vent.”

All vent piping should be graded to drain back to the drainage piping by gravity. The vent should be taken off above the cen-terline of the drainpipe and rise vertically or at an angle of not

more than 45° from the vertical. The horizontal run of the vent should be at least 6 in. above the overflow level of the fixture. (See Figure 4.)

relief VentSPressures in the drainage and vent stacks of a multistory build-ing are constantly fluctuating. The vent stack connection at the base of the drainage stack and the branch vent connections to the branch drains cannot always eliminate these fluctuations. It then becomes extremely important to balance pressures throughout the drainage stack by means of “relief vents” located at various intervals. The fluctuations in pressure may be caused by the simultaneous discharge of branches on various sepa-rated floors. Drainage stacks in buildings having more than ten branch intervals should be provided with a relief vent at each tenth interval, counting from the topmost branch downward. The lower end of the relief vent should connect to the drainage stack below the drainage branch connection and the upper end should connect to the vent stack at least 3 ft above the floor level. (See Figure 5.)

Relief vents are required where a drainage stack offsets at an angle of more than 45° to the vertical. Such offsets are subject to high pneumatic pressure increases and extreme surging flow

Figure 3 Various Fixture Trap Vents

Figure 4 Horizontal Run of Vent

Figure 5 Venting for Stacks Having More Than 10 Branch Intervals




conditions. The methods of installing relief vents are illustrated in Figure 6.

continuouS VentingA system of individual or common vents for every trap is called “continuous venting.” Every fixture trap is provided with a vent. It is the most expensive system but provides positive protection of all trap seals.

wet VentingA “wet vent” is a vent that vents a particular fixture and at the same time serves as a waste to receive the discharge from other fixtures. The objective of using wet vents is to minimize the vent piping required by employing one pipe to serve two functions. There are three fundamental rules to follow when utilizing a wet vent:

At top floor:1. No more than 1 FU is discharged into a 1½-in. wet vent nor

more than 4 FU into a 2-in. wet vent.

2. Length of drain does not exceed maximum permissible distance between trap and vent.

3. Branch connects to the stack at the water closet

connection level or below. (See Figure 7.)

At lower floors: The rules are the same except that the water closets must

be vented and the wet vent must be 2 in. minimum. Water closets below the top story need not be individually vented if a 2-in. wet vented waste pipe connects directly to the upper half of the horizontal water closet drain at an angle no greater than 45° from the angle of flow. (See Figure 8.)

“Stack venting” finds its general application in one-family homes and the top floor of multistory buildings. (See Figures 7 and 9.)

combination waSte and Vent Venting“Combination waste and vent venting” is used primarily for venting floor drains and laboratory and work tables. The drain-age piping is oversized at least two sizes larger than required for draining purposes only and the drainage branch and stack should be provided with vent piping. This type of venting is employed when it is impractical to employ the other methods.

circuit and looP VentingThere has developed a tendency to call all “circuit venting” by the name applicable to a special installation of circuit venting. A circuit vent is a branch vent that serves two or more floor outlet fixtures, except blowout water closets, and extends from in front of the last fixture connection on the horizontal drain to the vent stack. A “loop vent” is the same, except that it is employed on the topmost floor serving fixtures and is connected to the vent

Figure 8 Wet Venting Below Top Floor

Figure 7 Wet Venting at Top FloorFigure 6 Venting at Stack Offsets



extension of the drainage stack instead of to the vent stack. (See Figure 10.) When wall outlet fixtures are connected to the branch drain serving the floor outlet fixtures, the former must be provided with individual vents that can connect to the circuit vent or loop vent.

common VentSWhere two fixtures are connected to a vertical branch at the same level, a “common vent” may be employed. When one of the fixtures connects at a different level than the other, observe the following procedure. If fixture drains are the same size, increase the vertical drain one size. If fixture drains are of different sizes, connect the smaller above the larger connection and maintain the vertical size up to the top connection.

SudS PreSSureThe prevalent use of high-sudsing detergents in washing machines, dishwashers, laundry trays, and kitchen sinks has cre-ated serious problems in all residential buildings and especially in high-rise buildings. Until manufacturers are forced to market only detergents without sudsing characteristics, the plumbing engineer must understand and cope with the dangers created

in the sanitary system by the presence of suds. (An interesting sidelight is that suds, in and of themselves, do not enhance the cleaning ability of soaps or detergents in any way.)

When the flow of wastes from upper floors contains deter-gents, the sudsingredients are vigorously mixed with the water and air in the stack as the waste flows down the stack and further mixing action occurs as other branch waste discharges meet this flow. These suds flow down the stack and settle in the lower sec-tions drainage system and at any offsets greater than 45 degrees in the stack. Investigation has shown that when sudsing wastes are present, the sanitary and vent stacks are laden with suds and this condition was found to exist for extended periods of time.

Liquid wastes are heavier than suds and easily flow through the suds-loaded drainage piping without carrying the suds along with the flow. Everyone is aware of the difficulty of flushing the suds out of a sink. The water simply flows through the suds and out the drain, leaving the major portion of the suds behind. The same action occurs in the lower sections of the drainage system except for one important difference—air, as well as water, is now flowing in the piping. This air, which is carried down with the waste discharge, compresses the suds and forces them to move through any available path of relief. The relief path may be the building drain, any branches connected to the building drain, the vent stack, branch vents, individual vents or combinations of the foregoing. A path of relief may not always be available or could be cut off or restricted by the hydraulic jump, or a path may just be inadequate because of location or size. If one or more of these conditions exist, excessively high suds pressure can develop and blow the seals of traps with the accompanying appearance of suds in fixtures.

High suds pressure zones occur at every change in direction, vertically or horizontally, that is greater than 45°. Where vent stack base connections, relief vents, branch vents, or individual vents serve as the relief path for the high suds pressure, they

are usually found to be inadequate in size with resultant suds conditions appearing at the fixtures. The vent pipe sizing tables in practically every code are calculated on the basis of air flow capacity and do not in any way provide for the more demanding flow of suds. Sizes that are based on these code tables are inadequate to accommodate suds flow and thus are incapable of providing adequate suds pressure relief.

Suds are much heavier than air and consequently do not flow with the same ease. They produce a much greater friction head loss for the same rate of flow. The density of old or regenerated suds varies from 2 lb/ft3 to a high of 19 lb/ft3, depending upon the detergent used. For equal rates of flow and pressure loss, the vent pipe diameter for suds relief flow must be from 20 to 80% greater than for air flow.

Whenever a soil or waste stack receives washing machines, dishwashers, laundry trays, kitchen sinks, or other fixtures where sudsing detergents are used, the drainage and vent piping for the lower-floor fixtures or for the fixtures above offsets must be arranged to avoid con-nection to any zone where suds pressure exists.

Suds pressure zones exist in the following areas:

1. At a soil or waste stack offset greater than 45°: 40 stack diameters upward and 10 stack diameters horizontally from the base fitting for the

Figure 10 Circuit and Loop Venting

Figure 9 Stack Vented Unit




upper stack section. A pressure zone also exists 40 stack diameters upstream from the top fitting of the lower stack section.

2. At the base of a soil or waste stack: The suds pressure zone extends 40 stack diameters upward from the base fitting.

3. In the horizontal drain from the base of a stack: The suds pressure zone extends 10 stack diameters from the base fitting, and where an offset greater than 45° in the horizontal occurs, the pressure zones extend 40 stack diameters upstream and 10 diameters downstream from the offset fitting.

4. In a vent stack connected to a suds pressure zone: The suds pressure zone exists from the vent stack base connection upward to the level of the suds pressure zone in the soil or waste stack.

Figure 11 illustrates all the above zones.

VaPor VentS (local VentS)Years ago water closets and urinals were equipped with con-nections for venting the fixture to the outdoors to eliminate foul odors. Fixture design has been improved so that these vents are no longer required. The use of “vapor vents” is now applied to sterilizing equipment and bedpan washers. This application is also rapidly disappearing as new methods of condensing the foul vapors are being built into the equipment. When a vapor vent is used, it must be isolated from the sanitary venting system. The base of a vapor vent stack should terminate in a trap, to pre-vent the escape of vapors, and spill to a trapped, vented, and

water-supplied receptacle. The stack should extend through the roof.

An individual vapor vent drip can be connected through an air gap to the inlet of the trap serving the fixture. Vapor vents for bedpan washers and bedpan sterilizers must not connect with the vapor vents of other fixtures.Sizing of the vapor vent stack may be by empirical methods or the rational approach may be used. The minimum size of the stack should be 1¼ in.

ejector and SumP VentSEjectors, other than the pneumatic type, operate at atmo-spheric pressure and receive drainage discharge under grav-ity flow conditions. An ejector is installed when the level of fixture discharge is below the level of the public sewer. It is convenient to view an ejector system as being exactly simi-lar to the gravity sanitary system and all of the requirements for the proper design of the sanitary system are applicable. Thus, the air required to be conveyed by the vent piping is the same as the maximum rate at which sewage enters or is pumped out of the receiver.

The ejector vent can be determined by reference to Equa-tion 10:

L = 2226 ( d2 )fq2

and using Table 1, which gives air discharge in gpm for vari-ous pipe diameters. It has been found in practice that 3 in. is adequate except for extremely large installations.

froSt cloSureWhere the danger of frost closure of vent terminals is pres-ent, the minimum size of the vent stack or vent extension

through the roof should be 3 in. When a vent stack must be increased in size going through the roof, the increase should be made inside the building at least 1 ft below the roof.

The National Bureau of Standards has investigated the prob-lem of frost closure both theoretically and experimentally. It was demonstrated that a 3-in. vent terminal froze up solidly at -30°F only over an extended period of time. Closure occurs at the rate of 1½ in. for every 24 hr. that the temperature remains at -30°F.

It can be seen that frost closure presents a real problem only in the far northern regions. The problem is serious in Canada, and they have devised various methods of overcoming it:

1. Vent terminal to extend only 1 in. or 2 in. above the roof. The more pipe exposed to the atmosphere, the greater the problem. Snow covering the vent terminal has proven to cause no trouble. The snow is porous enough for the passage of air and melts rather rapidly at the outlet.

2. Enlargement of the stack below the roof. The increased diameter decreases the chance of complete closure and the stream of air tends to flow through the enlarged portion without touching the walls of the enlarged pipe.

3. Install cap flashing at the terminal and counterflashing to leave an air space from the heated building.

Frost closure depends upon the: (1) outside temperature, (2) temperature and humidity of inside air, (3) wind velocity, (4) length of exposed pipe, (5) diameter of exposed pipe, and (6) velocity of air flow. There is very little danger of frost closure unless the outside temperature falls below -10°F and remains

Figure 11 Suds Pressure Zones



there for several days. It has been found that if frost closure does occur, siphonage of traps is reduced or prevented by connecting the drainage and vent stacks together before extending through the roof. An analysis of air flow under these conditions will con-vince the plumbing engineer of its validity, as it can be seen that air forced into the vent stack at its base will be introduced into the soil stack at the top connection.

teStS of Plumbing SyStemSThe complete storm and sanitary system should be subjected to a water test and proven watertight upon completion of the rough piping installation and prior to covering or concealment. The test pressure should be a minimum of a 10-ft column of water except for the topmost 10 ft of pipe. The test pressure should never exceed a maximum of a 100-ft column of water. Any greater pressure will cause the test plugs used to seal temporarily open piping in the system to blow. If the system is higher than 100 ft, test tees may be installed at appropriate heights so as to test the building in sections. Very rarely in practice are more than seven stories tested at one time.

If it is not possible to perform a water test, an air test is accept-able. The air test shall be made by attaching an air compressor testing apparatus to any suitable opening, and, after closing all other inlets and outlets to the system, forcing air into the system until there is a uniform gage pressure of 5 psi (34.5 kPa) or a pressure sufficient to balance a column of mercury 10 in. (254 mm) in height. The pressure shall be held without introduction of additional air for a period of at least 15 min.

Upon completion of the sanitary system and after all fixtures are installed with traps filled with water, the system should be subjected to an additional test and proved gastight.

An alternate test is the smoke test. The smoke test is performed by introducing pungent, thick smoke produced by smoke bombs or smoke machines. When smoke appears at the roof terminals, each terminal is sealed and a smoke pressure of 1-in. column of water is maintained to prove the system gastight. This test is not practical and is seldom used.

Another alternate test is the peppermint vapor test. At least 2 oz. of oil of peppermint are introduced into each roof terminal and vaporized by immediately pouring 10 qt of boiling water down the stack. The terminals are promptly sealed. Oil of pepper-mint and any person coming in contact or handling the oil must be excluded from the interior of the building for the duration of the test. Leakages will be detected by the peppermint odor at the source. However, it is very difficult to pinpoint the leak by this method. This test is not practical and is seldom used.





PSD

137


CE Questions—“Vent Systems” (PSD 137)

About This Issue’s ArticleThe January/February 2007 continuing education article is

“Vent Systems,” Chapter 8 of Engineered Plumbing Design II by A. Calvin Laws, PE, CPD.

Flow of air is the primary consideration in the design of a venting system for the ventilation of the piping and protection of the fixture trap seals of a sanitary drainage system. Since air is of such primary importance, it is essential that the plumbing engineer be familiar with certain physical characteristics that are pertinent to its behavior in a plumbing system. This chapter explains these fundamentals that are vital to the design of a vent system. It also covers vent stacks, the various types of vents and venting, the effects of suds pressure, frost closure, and vent system pressure tests.




at www.psdmagazine.org. The following exam and application form also may be downloaded from the Web site. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. For most people, this process will require approximately one hour. If you earn a grade of 90 percent or higher on the test, you will be notified that you have logged 0.1 CEU, which can be applied toward the CPD renewal requirement or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for three years.


1. A wet vent is ___________.a. not allowed by most codesb. a vent that vents a particular fixture and at the same

time serves as a waste vent to receive the discharge from other fixtures

c. not allowed to serve water closetsd. a system of individual or common vents for every trap

. The vent piping must be designed to permit the air to ___________.a. flow freelyb. enter the piping networkc. exit the piping networkd. be compressed

. Suds, in and of themselves, ___________.a. do not enhance the cleaning ability of soaps or

detergents in any wayb. are only a problem if they are allowed to accumulate in

large numbersc. require wet venting to rinse the suds out of the drain

piped. none of the above

. The most expensive venting system is a ___________ system.a. wet vent, b. continuous vent, c. circuit vent, d. loop vent

. Vapor vents ___________.a. must be isolated from the sanitary venting systemb. may be connected through an air gap to the trap

serving the fixturec. must not be connected to the vapor vents of other

types of equipmentd. all of the above

. To compensate for suds density, the vent pipe for suds relief flow must ___________.a. not be depended on for suds protectionb. connect to each fixture trap

c. connect 10 pipe diameters from any high pressure suds zone

d. be 20 percent to 80 percent larger in diameter

. What is the primary consideration in the design of a venting system?a. removing odors from the sewer systemb. correctly sizing the vent piping to match the size of the

waste pipingc. the flow of air in the vent systemd. none of the above

. For a given rate of discharge from a lavatory, decreasing the diameter of the drain will ___________.a. increase the water discharge velocity from the fixtureb. decrease the water discharge velocity from the fixturec. increase trap seal lossesd. prevent trap seal losses

. Smoke tests and peppermint air tests ___________.a. can detect the location of a leak in a vent systemb. are no longer allowed by OSHA and the EPAc. are not practical and seldom usedd. may not be used where frost closure is expected

10. A column of air . feet high exerts the same pressure as a column of water ___________ high.a. 1 inch, b. 10 inches, c. 100 inches, d. 1,000 inches

11. A branch vent interval is ___________.a. determined by the floor-to-floor height of the buildingb. dependent on the arrangement of the fittings

connecting at each floorc. at least 8 feet between branchesd. of no importance in modern plumbing systems

1. The maximum distance of a vent to a -inch-diameter trap is ___________.a. 30 inches, b. 42 inches, c. 60 inches, d. 72 inches








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PS&D Continuing Education Answer SheetVent Systems (PSD 137)


Appraisal QuestionsVent Systems (PSD 137)






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Expiration date: Continuing education credit will be givenfor this examination through January 1, 00.Applications received after that date will not be processed.








PSD

138

Water System Design


MARCH/APRIL 2007

PSDMAGAZINE.ORG


The objective in designing the water supply systems for any project is to ensure an adequate water supply at adequate pres-sure to all fixtures and equipment at all times and to achieve the most economical sizing of the piping.

There are at least six important reasons that proper design of water distribution systems is absolutely essential:

1. Health. This is of irrefutable and paramount importance. Inadequate or improper sizing can cause decreases in pressure in portions of the piping system, which in turn can cause contamination of the potable water supply by backflow or siphonage. There are too many well-docu-mented deaths attributable to this cause.

2. Pressure. It is essential to maintain the required flow pres-sures at fixtures and equipment or improper operation will result.

3. Flow. Proper and adequate quantities of flow must be maintained at fixtures and equipment for obvious reasons.

4. WaterSupply. Improper sizing can cause failure of the water supply due to corrosion or scale buildup.

5. PipeFailure. Pipe failure can occur due to the relation of the rate of corrosion with excessive velocities.

6. Noise. Velocities in excess of 10 ft/sec will cause noise and increase the danger of hydraulic shock.

Of all the complaints resulting from improperly designed water systems, the two that occur most frequently are (1) lack of adequate pressure and (2) noise.

Noise may not be detrimental to the operation of a water dis-tribution system but it is very definitely a major nuisance. The lack of adequate pressure, however, can have very serious reper-cussions in the operation of any water system.

Flow PressureIt is essential that the term flow pressure be thoroughly under-stood and not confused with static pressure. Flow pressure is that pressure that exists at any point in the system when water is flow-ing at that point. It is always less than the static pressure. To have flow, some of the potential energy is converted to kinetic energy and additional energy is used in overcoming friction, which results in a flow pressure that is less than the static pres-sure.

When a manufacturer lists the minimum pressure required for the proper operation of a flush valve as 25 psi, it is the flow pressure requirement that is being indicated. The flush valve will not function at peak efficiency (if at all) if the engineer has erroneously designed the system so that a static pressure of 25 psi exists at the inlet to the flush valve.

Flow at an outletThere are many times when the engineer must deter-

mine how many gallons per minute are being delivered at an outlet. This can easily be determined by installing a pressure gauge in the line adjacent to the outlet and

reading the gauge while flow is occurring. With the flow pres-sure known, the following formula can be used:

(1)q = 20d2 p½

where q = rate of flow at the outlet, gpm d = actual inside diameter (ID) of outlet, in. p = flow pressure, psi

Assume a faucet with a 3⁄8-in. supply and the flow pressure is 16 psi. Then: q = 20 × (3⁄8)2 × (16)½

= 20 × 9⁄64 × 4 = 11.25 gpm

The flow for a ¼-in. and 1⁄8-in. supply at the same pressure would be 5 gpm and 1.25 gpm, respectively.

Constant FlowPressures in the various parts of the piping system are con-stantly fluctuating depending upon the quantity of flow at any moment. Under these conditions the rate of flow from any one outlet will vary with the change of pressure. In industrial and laboratory projects there is some equipment that must be sup-plied with a fixed and steady quantity of flow regardless of line pressure fluctuations. This feature is also desirable in any type of installation.

This criterion can easily be achieved by the utilization of an automatic flow-control orifice. A flow control is a simple, self-cleaning device designed to deliver a constant volume of water over a wide range of inlet pressures. (See Figures 1 and 2.) The automatic controlling mechanism consists of a flexible orifice that varies its cross-sectional area inversely with the pressure so that a constant flow rate is maintained under all conditions. Until the inlet pressure reaches the threshold pressure (12–15 psi), the flexible insert acts as a fixed orifice. When the thresh-old pressure is exceeded, the cross-sectional area of the orifice is decreased by the flexure of the insert. This causes a pressure drop that is equal to whatever pressure is necessary to absorb the energy not required to overcome system friction and to

Water System Design

Reprinted from Engineered Plumbing Design II, Chapter 13: “Water System Design,” by A. Calvin Laws, PE, CPD.© American Society of Plumbing Engineers.

Figure 1 Flow Control

Plumbing Systems & Design MARCH/APRIL 2007 PSDMAGAZINE.ORG



sustain the rated flow. The curve shown in Figure 2 is typical of most flow controls regardless of the rated flow, which is why no figures are shown for the gallons per minute axis. It is possible to approximate the flow of a specific flow control by using the line marked “Nominal Flow Rate” as the desired rate.

Assume a piece of equipment requires the fixed flow of 40 gpm and there is considerable line pres-sure fluctuation. A flow control would be specified to deliver 40 gpm. By use of the curve in Figure 2 the deviation from 40 gpm at various pressures can be read by assigning a value of 40 to the nominal flow rate line on the vertical scale and zero to the baseline. Standard flow controls are available in sizes from ¼ in. to 2½ in. and flow rates from ¼ to 90 gpm. They are ideal for use in limiting the maximum rate of flow to any fixture.

It is not unusual in a water distribution system to experience fluctuating discharges at fixtures and equipment due to other fixtures and equipment start-ing up or shutting down. Flow controls will minimize

these problems because they automatically com-pensate for changes in the line pressure to hold the rate of water delivery from all outlets to a preselected number of gallons per minute. One very important word of caution—a flow control is not designed to perform the function of pressure regulation and should never be used where a pressure-regulating valve is required.

Material seleCtionBefore the type of material for the piping of a water distribution system can be selected, certain factors must be evaluated:

1. The characteristics of the water supply must be known. What is the degree of alkalinity or acidity? A pH above 7 is alkaline and below 7 is acidic. A pH of 7 represents neutral water. What is the air, carbon dioxide, and mineral content? The municipal water supply department can usually furnish all this information. If it is not available, a water analysis should be made by a qualified laboratory.

2. What are the relative costs of the various suitable materials?

3. Ease of replacement—can the material be obtained in a reasonable time or must it be shipped from localities that might delay arrival for months?

4. Actual inside dimensions of the same nominal size of vari-ous materials differ. This variation in ID can have a signifi-cant effect on sizing because of the variation in quantity rates of flow for the same design velocity. Table 1 shows the actual ID for various materials.

5. The roughness or smoothness (coefficient of friction) of the pipe will have a marked effect on pipe sizes.

Parallel CirCuitsThere are many parallel pipe circuits in the water distribution system of any job. An arrangement of parallel pipe circuits is one in which flow from a single branch divides and flows in two or more branches which again join in a single pipe. Figure 3 illustrates a simple two-circuit system. The total flow enter-ing point A is the same leaving point A with a portion flowing through branch 1 and the rest through branch 2. Flows q1 and q2 must equal q and the total pressure drop from A to B is the same

Figure 2 Flow Control Device Curve (Dole Valve)

Figure 3 Typical Parallel Pipe Circuit

Nominal Pipe Size,

In.

Iron or Steel Pipe, Sch.

40

Brass or Copper Pipe

Copper Water Tube, Type K

Copper Water Tube, Type L

½ 0.622 0.625 0.527 0.545¾ 0.824 0.822 0.745 0.7851 1.049 1.062 0.995 1.025

1¼ 1.380 1.368 1.245 1.2651½ 1.610 1.600 1.481 1.505

2 2.067 2.062 1.959 1.9852½ 2.469 2.500 2.435 2.465

3 3.068 3.062 2.907 2.9454 4.026 4.000 3.857 3.9055 5.047 5.062 4.805 4.8756 6.065 6.125 5.741 5.8458 7.981 8.001 7.583 7.725

10 10.020 10.020 9.449 9.625

Table 1 Actual Inside Diameter of Piping,in Inches

MARCH/APRIL 2007 Plumbing Systems & Design


whichever branch is traversed. The rate of flow through each branch becomes such as to produce this equal pressure drop. The division of flow in each branch can then be expressed as:

(2)

q1 =Ö L2 ( d1 )5

q2 L1 d2

Assume there is a flow in a 3–in. pipe of 160 gpm entering point A and leaving point B as shown in Figure 4. The length of branch 1 is 20 ft and branch 2 is 100 ft. The size of branch 1 is 2 in. and branch 2 is 3 in. To determine the quantity of flow in each branch, the basic formula is applied, and:

q1 =Ö 100 ( 2 )5

q2 20 3

= Ö5 (.66)5

= Ö5 × 0.125= 0.79

q1 = 0.79q2

since q1 + q2 = 160

then 0.79q2 + q2 = 160

1.79q2 = 160q2 = 89.4 gpm

and q1 = 160 - 89.4 = 70.6 gpm

or q1 = 0.79 × 89.4 = 70.6 gpm

inadequate PressureAs previously noted, lack of adequate pressure is one of the most frequent complaints and could be the cause of serious troubles. The pressure available for water distribution within a building can come from various sources. Municipalities usually maintain water pressure in their distribution mains within the range of 35–45 psi. There are localities where the pressure maintained is much less or greater. The local utility will furnish the information as to their minimum and maximum operating pressures. When utilizing only the public water main pressure for the water dis-tribution system within a building, it is very important to deter-mine the pressure available in the mains during the summer months. Huge quantities of water are used during this period for sprinkling of lawns and for air-conditioning cooling tower

makeup water, which usually cause excessive pres-sure loss in the mains. Future growth of the area must also be analyzed. If large housing, commer-cial, or industrial development is anticipated, the pressure available will certainly decrease as these loads are added to the public mains. It is good practice to assume a pressure available for design purposes as 10 psi less than the utility quotes.

If the pressure from the public mains is inade-quate for building operation, other means must be provided for increasing the pressure to an adequate level. There are three basic methods available:

1. Gravity tank system2. Hydropneumatic tank system3. Booster pump system

Each system has its own distinct and special advantages and disadvantages. All three should be evaluated in terms of capital expenditure, operat-ing costs, maintenance costs, and space require-

ments. Depending upon which criteria are the most important, this will dictate which system is selected.

Flow deFinitionsMaximum flow or maximum possible flow is the flow that will occur if the outlets on all fixtures are opened simultaneously. Average flow is that flow likely to occur in the piping under normal conditions. Maximum probable flow is the maximum flow that will occur in the piping under peak conditions. It is also called peak demand or peak flow.

deMand tyPesSome outlets impose what is called a continuous demand on the system. They are differentiated from outlets that impose an intermittent demand. Outlets such as hose bibbs, lawn irriga-tion, air-conditioning makeup, water cooling, and similar flow requirements are considered to be continuous demands. They occur over an extended period of time. Plumbing fixtures draw water for a relatively short period of time and are considered as imposing an intermittent demand.

Each fixture has its own singular loading effect on the system, which is determined by the rate of water supply required, the duration of each use, and the frequency of use. The water demand is related to the number of fixtures, type of fixtures, and probable simultaneous use.

estiMating deMandThe basic requirements for estimating demand call for a

method that1. Produces estimates that are greater than the average

demand for all fixtures or inadequate supply will result during periods of peak demand.

2. Produces an accurate estimate of the peak demand to avoid oversizing.

3. Produces estimates for demand of groups of the same type of fixtures as well as for mixed fixture types.

design loadsArriving at a reasonably accurate estimate of the maximum probable demand is complicated due to the intermittent opera-tion and irregular frequency of use of fixtures. Different kinds of fixtures are not in uniform use. Bathroom fixtures are most frequently used on arising or retiring and, not surprisingly, during television commercials. Kitchen sinks find heavy usage

Figure 4 Example of Division of Flow in a Parallel Pipe Circuit


CONTINUING EDUCATION: Water System Design


before and after meals. Laundry trays and washing machines are most likely to be used in the late morning. During the period from midnight to 6 P.M. there is very little fixture use. Luckily, fixtures are used intermittently and the total time in operation is relatively small so it is not necessary to design for the maximum potential load. Maximum flow is therefore of no real interest to the designer. Average flow is also of no concern, for if a system were designed to meet this criterion it would not satisfy the con-ditions under peak flow. It is therefore necessary to consider only the maximum probable demand (peak demand) imposed by the fixtures on a system.

Two methods have evolved in the United States that, when used where applicable, have proven to give satisfactory results. They are the empirical method and method of probability. The empirical method is based upon arbitrary decisions arrived at from experience and judgment. It is useful only for small groups of fixtures. The method of probability is based upon the theory of probabilities and is most accurate for large groups of fixtures.

In the past, certain demand rates became generally accepted as standard. These rates are tabulated in Table 2 for the common types of fixtures and the average pressure necessary to deliver this rate of flow. The actual pressure for a specific fixture will vary with each manufacturer’s design, some requiring a greater or lesser pressure than others.

Although the flow rates shown in Table 2 have been used by engineers, they are hopelessly outdated. Water conservation measures being mandated by federal regulations and model codes make the flow rates shown in Table 2 unreasonable for use in the design of systems. The federal Energy Policy Act (EPACT92) established the following criteria for water use by fixture: Water closets: 1.6 gal/flush Urinals: 1.5 gal/flush Showers: 2.5 gpm Lavatories: 2.5 gpm Sinks: 2.5 gpm

Manufacturers offer fixtures meeting these and more stringent requirements. Lavatories with 0.5 gpm flow rates and urinals with 1.0 gal/flush have been installed in thousands of buildings with satisfactory results. However, there is a need for research to determine the actual minimum flow required, for each type of fixture, to satisfy psychological requirements of the user and provide the necessary sanitary requirements.

water suPPly Fixture unitsA standard method for estimating the water demand for a build-ing has evolved through the years and has been accepted almost unanimously by plumbing designers. It is a system based on weighting fixtures in accordance with their water supply load-producing effects on the water distribution system. The National Bureau of Standards has published report BMS 65, Methods of Estimating Loads in Plumbing Systems, by the late Dr. Roy B. Hunter, which gives tables of load-producing characteristics (fixture unit weights) of commonly used fixtures, along with probability curves that make it possible to apply the method easily to actual design problems.

The method of probability should not be used for a small number of fixtures. Although the design load, as computed by this method, has a certain probability of not being exceeded, it may nevertheless be exceeded on rare occasions. When a system contains only a few fixtures, the additional load imposed by one fixture more than has been calculated by the theory of probability can easily overload the system. When a system con-tains a large number of fixtures, one or several additional fixture loadings will have an insignificant effect on the system.

In developing the application of the theory of probability to determine design loads on a domestic water distribution system, Hunter assumed that the operation of the fixtures in a plumb-ing system could be viewed as purely random events. He then determined the maximum frequencies of use of the fixtures. He obtained the values of the frequencies from records collected in hotels and apartment houses during the periods of heaviest usage. He also determined characteristic values of the average rates of flow for different fixtures and the time span of a single operation of each.

If only one type of fixture were used in a building, the appli-cation of the theory of probability would be very simple and straightforward. When dealing with systems composed of various types of fixtures that must be combined, the process becomes extremely involved and too complicated to be of any practical use. Faced with this dilemma, Hunter devised an inge-nious method to circumvent the problem by a simple process which yields results within ½% accuracy of the more involved and laborious calculations required. He conceived the idea of assigning “fixture loading factors” or “fixture unit weights” to the different kinds of fixtures to represent the degree to which they loaded a system when used at their maximum assumed frequency. A fixture unit weight of 10 was arbitrarily assigned by Hunter to a flush valve, and all other fixtures were assigned values based on their load-producing effect in relation to the flush valve. All fixtures have been converted, in essence, to one fixture type and the application of the theory of probability is greatly simplified.

Hunter assigned water supply fixture unit (FU) values for dif-ferent kinds of fixtures, which are given in Table 3. Conversion of fixture unit values to equivalent gallons per minute, based on the theory of probability of usage developed by Hunter, is given in Table 4. A graphic representation of this table is shown by Figures 5 and 6 (Hunter’s Curve). Figure 7 gives a graphic rep-resentation of the conversion from fixture units to gallons per minute for a mixed system. An examination of the curves and tables reveals that demand for a system utilizing flush valves is much greater than that for flush tanks for small quantities. The difference in demand for each system decreases as the fixture unit load increases until 1,000 FUs are reached. At this loading and beyond, the demand for both types of systems is the same.

Fixture Flow Pressure, psi

Flow Rate, gpm

Ordinary lavatory faucet 8 3.0Self-closing lavatory faucet 12 2.5Sink faucet, 3∕8 in. 10 4.5Sink faucet, ½ in. 5 4.5Bathtub faucet 5 6.0Laundry tub faucet, ½ in. 5 5.0Shower head 12 5.0Water closet flush tank 15 3.0Water closet flush valve, 1 in. 10–25 15–45Urinal flush valve, ¾ in. 15 15.0Hose bibb or sill cock, ¾ in. 30 5.0

Table 2 Demand at Individual Fixtures and Required Pressure



Fixture or Group OccupancyType of Supply

ControlFixture Units

Hot Cold TotalWater closet Public Flush valve — 10 10Water closet Public Flush tank — 5 5Pedestal urinal Public Flush valve — 10 10Stall or wall urinal Public Flush valve — 5 5Stall or wall urinal Public Flush tank — 3 3Lavatory Public Faucet 1.5 1.5 2Bathtub Public Faucet 3 3 4Shower head Public Mixing valve 3 3 4Service sink Office, etc. Faucet 3 3 4Kitchen sink Hotel or restaurant Faucet 3 3 4Water closet Private Flush valve — 6 6Water closet Private Flush tank — 3 3Lavatory Private Faucet .75 .75 1Bathtub Private Faucet 1.5 1.5 2Shower head Private Mixing valve 1.5 1.5 2Bathroom group Private Flush valve W.C. 2.25 6 8Bathroom group Private Flush tank W.C. 2.25 4.5 6Separate shower Private Mixing valve 1.5 1.5 2Kitchen sink Private Faucet 1.5 1.5 2Laundry tray Private Faucet 2 2 3Combination fixture Private Faucet 2 2 3

Table 3 Demand Weight of Fixtures, in Fixture Units

Figure 6 Conversion of Fixture Units to gpm (enlarged scale)

Figure 5 Conversion of Fixture Units to gpm

Demand (Load)

Fixture Units

Demand (Load), gpm System with Flush Tanks

Demand (Load), gpm System with Flush Valves

1 0 —2 1 —3 3 —4 4 —5 6 —6 5 —8 6.5 —

10 8 2712 9 2914 11 3016 12 3218 13 3320 14 3525 17 3830 20 4135 23 4440 25 4745 27 4950 29 5260 32 5570 35 5980 38 6290 41 65

100 44 68120 48 73140 53 78160 57 83180 61 87200 65 92225 70 97250 75 101275 80 106300 85 110400 105 126500 125 142750 170 178

1,000 208 2081,250 240 2401,500 267 2671,750 294 2942,000 321 3212,250 348 3482,500 375 3752,750 402 4023,000 432 4324,000 525 5255,000 593 5936,000 643 6437,000 685 6858,000 718 7189,000 745 745

10,000 769 769

Table 4 Conversion of Fixture Units to Equivalent gpm


CONTINUING EDUCATION: Water System Design


For hot water piping and where there are no flush valves on the cold water piping, the demand corresponding to a given number of fixture units is determined from the values given for the flush tank system.

The accuracy of Hunter’s curve, however, has come into seri-ous question. Results utilizing the curve have proven to be as much as 100% inflated in some instances. The consistent overde-sign, however, should in no way be interpreted as indicating that Hunter’s basic research and approach are incorrect.

His method is demonstrably accurate, but it must be remem-bered that his basic assumptions and criteria were promulgated more than 60 years ago. Many things have changed, and changed drastically, in the interim. Improvements have been made in flush valve design as well as in faucets and fixtures. Social cus-toms and living patterns have changed. The public emphasis on water and energy conservation has altered many basic criteria. It is now necessary to change some of Hunter’s basic assump-tions (but not his concept).

It has been demonstrated by thousands of projects operating satisfactorily that it is safe to reduce the values obtained by use of Hunter’s curve by 40%. It is stressed again that this reduction can be applied only for systems with a large number of fixtures. The opposite is true for water use in toilet facilities where large numbers of people gather, such as sport facilities and auditori-ums. In these types of facilities, demand flow rates will exceed those determined by Hunter’s curve because many people will use the toilet rooms during breaks in the game or performance.

The student is again warned to use the table of fixture unit values in the code applicable to the locality of the project. The values vary slightly from code to code. The student is also alerted to the fact that water supply fixture units are not the same as

drainage fixture unit values. The discharge rates of cer-tain fixtures are entirely different from the rate at which water is supplied, e.g., bathtubs. The loading effect is therefore different on the drainage system than it is on the water supply system for specific fixtures.

For supply outlets that are likely to impose continuous demands, estimate the continuous demand separately from the intermittent demand and add this amount in gallons per minute to the demand of the fixtures in gal-lons per minute.

It should be kept in mind when calculating maxi-mum probable demands that, except for continuous demands, fixture unit values are always added, never gpm values. For example, if the maximum probable demand for two branches is required and one branch has a load of 1250 FU and the other 1750 FU, it would be wrong to add 240 gpm + 294 gpm to obtain 534 gpm for the total demand. The correct procedure is to add 1250 FU + 1750 FU to obtain a total FU value of 3000 and then from Table 4 determine the correct peak demand as 432 gpm. The 432 gpm value reflects the proper application of the theory of probability.

The following example illustrates the procedure for sizing a system.

Example 1Determine the peak demands for hot and cold and

total water for an office building that has 60 flush valve water closets, 12 wall hung urinals, 40 lavatories, and 2 hose bibbs and requires 30 gpm for air-conditioning water makeup.

From Table 3 determine the FU values:Hot Water Cold Water Total (Hot & Cold)

60 WC × 10 — 600 60012 UR × 5 — 60 6040 Lavs × 2 — — 8040 Lavs × 1.5 60 60 —

60 FU 720 FU 740 FU

From Table 4 or Figure 5:

60 FU = 32 gpm hot water demand720 FU = 174 gpm cold water demand740 FU = 177 gpm total water demand

To the cold water and total water demand must be added the continuous demand:

2 hose bibbs × 5 (from Table 2) = 10 gpmAir-conditioning makeup = 30 gpm 40 gpm

Then:Hot water demand: = 32 gpmCold water demand: 174 + 40 = 214 gpmTotal water demand: 177 + 40 = 217 gpm

The conversion of fixture unit loads to equivalent gallons per minute demand was obtained from Table 4 using straight line interpolations to obtain intermediate values. Total water demand is required for sizing the water service line for the building and also for the cold water piping inside the build-ing up to the point where the connection is taken off to the hot water heater supply.

Figure 7 Conversion of Fixture Units to gpm (Mixed System)




About This Issue’s ArticleThe March/April 2007 continuing education article is “Water

System Design,” Chapter 13 of Engineered Plumbing Design II by A. Cal Laws, PE, CPD.

The objective in designing the water supply systems for any project is to ensure an adequate water supply at adequate pressure to all fixtures and equipment at all times and to achieve the most economical sizing of the piping. There are at least six important reasons why proper design of water distri-bution systems is absolutely essential: health, pressure, flow, water, pipe failure, and noise. This chapter describes how to design an effective water system keeping these factors in mind, focusing on pressure, flow, and demand.


PSD

138


CE Questions—“Water System Design” (PSD 138)1. The flow of water through two parallel circuits of

different pipe sizes results in a pressure loss _________. a. of equal proportions in each circuitb. higher in the circuit with the smaller pipe sizec. lower in the circuit with the larger pipe sized. that is double compared to a single piping run

. The accuracy of Hunter’s Curve has been proven to be _________ percent inflated.a. 25b. 50c. 75d. 100

. The coefficient of friction is the measurement of _______ in piping.a. pressure dropb. velocityc. roughness or smoothnessd. none of the above

. Flow rates shown in Figure are _________.a. generally accepted by system designersb. hopelessly outdatedc. unreasonable for use in designing systemsd. b and c

. Pipe failure can be caused by corrosion from _________.a. contaminated waterb. excessive velocitiesc. softened waterd. hot water

. The actual inside diameter of ½-inch Type K copper tube is _________.a. 2.435 inchesb. 2.465 inchesc. 2.469 inchesd. 2.500 inches

. The empirical method is _________.a. based on arbitrary decisionsb. cannot be duplicatedc. allowed only by the most out-of-date codesd. used only by the most senior and the most junior of

designers

8. Research is required to _________.a. determine the actual minimum flow required for each

fixture typeb. satisfy the psychological requirements of the usersc. provide the necessary sanitary requirementsd. all of the above

9. The pressure that exists in a piping network at any point when water is flowing is considered _________.a. static Pressureb. residual Pressure c. flow pressured. none of the above

10. The probability method _________.a. works for all plumbing systemsb. unanimously accepted by plumbing engineersc. should not be used for small numbers of fixturesd. a and b

11. The two methods of sizing domestic water, empirical method and method of probability, _________.a. are contradictoryb. give satisfactory resultsc. cannot be relied upond. have been replaced by computer-based methods

1. An automatic flow control orifice is designed to _______.a. regulate pressureb. deliver constant flowc. restrict pressured. increase pressure





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PS&D Continuing Education Answer SheetWater System Design (PSD 138)

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59284471 Plumbing Systems Advanced

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