ELEMENTS OF CIVIL ENGINEERING

Course instructor

Plumbing for Buildings

Course instructor

Dr. Trudeep N. Dave (Ph.D. – IIT Bombay)

Assistant Professor

Department of Civil Engineering,

School of Technology

Pandit Deendayal Petroleum University

E-mail: trudeep.dave@sot.pdpu.ac.in

Introduction

�Various fittings used for use of water and for drainage of used water

are known as sanitary fittings. The services like water supply, drainage,

sanitation etc. are known as plumbing services.

� A plumbing water supply system comprises of water supply and

distribution pipes, taps, valves, storage tanks etc., while plumbing

drainage system consists of wash basin, water closets, urinals, traps,

soil waste pipes, vent pipes, septic tanks etc.soil waste pipes, vent pipes, septic tanks etc.

Important points for laying out the Pipe lines

� The lines should be so laid that there is no risk involved in the

contaminating of water supply. For this, following three things are

necessary:

a) There is no cross-connection any where between a pipe carrying

possible water and the pipe carrying used or waste water.

b) There should be no back flow from any cistern or appliance towards

the source of supply.

c) Water supply pipes and waste water pipes (drainage pipes) shouldc) Water supply pipes and waste water pipes (drainage pipes) should

not be laid very close to each other.

� The pipe line should be properly protected against any damage.

� In the unfeed system, pipe should carry water under adequate

pressure. The pipes should be laid out as straight as possible.

Storage Tanks

� The water supply to a building may either be continuous or

intermittent. The storage tanks may be situated either at the

ground level, or at the roof level or at both the levels.

� A storage tank is made of (a) mild steel pressed plates (b)

reinforced concrete, or (c) stone or brick masonry.

A storage tank consists of following accessories:

1. Top cover – made of mild steel / aluminum/ other suitable material, light

in weight and tight fitting so that mosquitoes do not enter. It may have

locking arrangement.

2. Ball valve with float - which is provided near the inlet to the tank, so as to

control the inflow of water. The float assembly works automatically, thus

maintaining a constant water level in the tank. When the water level falls

down, the float moves down thus opening the inlet valve. When the level

in tank reaches the desired full supply level (F.S.L.), the float rises up thusin tank reaches the desired full supply level (F.S.L.), the float rises up thus

closing the inlet valve.

3. Over flow pipe – which is set about 2.5 cm F.S.L. In case the float

assembly fails, the inflow is not cutoff and the water entering the tank

overflows through this pipe.

4. Supply pipe/Inlet pipe, admitting water into the tank.

5. Outlet pipe with stop valve set about 2.5 to 5 cm above the bottom of the

tank, for cutting off the supply to down tank pipes.

6. Drain pipe or scour pipe for cleaning the tank periodically.

The capacity of storage tank depends upon the following factors:

i) Supply hours from the mains, with sufficient pressure

ii) Frequency with which the tank can be refilled during 24 hours.

iii) Rate and regularity of supply.

In the case of multi storeyed building, the first two or three storeys

may be fed directly from the water upper storeys are fed from the

storage tanks.

Capacity of Storage Tank

storage tanks.

Flushing Storage Tank

These tanks are required to supply water to the various flushing

cisterns through down tank pipes. The supply pipes of a building

do not directly fed water to these cisterns. The storage capacities

for flushing purpose depend upon the number of water closets

(W.C.) and urinals in abuildings.

House Drainage : General Principles

Aims of house drainage:

1. To maintain healthy conditions in the building

2. To dispose off waste as early and quickly as possible

3. To avoid the entry of foul gases from the sewer or the septic tank

4. To facilitate quick removal of foul matter (e.g. human excreta)

5. To collect and remove waste matters systematically

Principles of house drainage:Principles of house drainage:

1. The lavatory block should be so located that the length of drainage line is

minimum.

2. The drainage pipes should be laid by the side of the building rather than

below the building.

3. All the drains should be aligned straight between successive inspection

chambers. All sharp bends and junctions should be avoided except

through chambers.

4. The slope of the drains should be sufficient to develop self cleansing

velocity.

5. The size of drain should be sufficient, so that flooding of the drain does

not take place while handling the maximum discharge.

6. The drainage system contain enough number of traps at suitable

locations.

7. The house drain should be disconnected to the public sewer b the

provision of an intercepting trap. This will avoid the entry of foul gases

from entering the house drainage system. It should be seen that the

public sewer is deeper than the house drain.

8. Rain water pipes should drain out rain water directly into the street

gutters from where it is carried to the storm draingutters from where it is carried to the storm drain

9. All the connections should be water tight.

10. The entire drainage system should be properly ventilated from the

starting point to the final point of disposal. It should permit free

circulation of air.

11. All the materials and fittings of the drainage system should be hard,

strong and resistant to corrosive action. They should be non-absorbent

type.

12. The entire system should be so designed that the possibilities of

formation of air locks, siphonage, under deposits etc. are minimized.

Pipes and Traps

Pipes may be classified as following depending on their function:

1. Soil pipe: A pipe through which human excreta flows (Dia. – 100 mm)

2. Waste pipe: A pipe which carries only the liquid waste, doesn’t carry

human excreta (hori. pipe dia. – 30 to 50 mm, vert. pipe dia. – 75 mm )

3. Vent pipe: A pipe which is provided for the purpose of the ventilation of

the system. A vent pipe is open at top and bottom, to facilitate exit of foul

gases. It is carried at least 1 m higher than the roof level. (Dia. – 50 mm)

4. Rain water pipe: A pipe which carries only rain water. (Dia. – 75 mm)4. Rain water pipe: A pipe which carries only rain water. (Dia. – 75 mm)

5. Anti-siphonage pipe: A pipe which is installed in the house drainage to

preserve the water seal of traps. (Connecting soil pipe dia. – 100 mm)

(Connecting waste pipe dia. – 100 mm)

Traps: Definition: A trap is a depressed or bent fitting which, when

provided in a drainage system, always remains full of water, thus

maintaining a water seal. It prevents the passage of foul air or gas

through it, though it allows the sewage or waste water to flow through it.

The depth of water seal represents its strength and effectiveness. Greater the

depth of water seal, more effective is the trap. The depth of water seal

varies from 25 mm to 75 mm.

Characteristics of traps:

1. It should possess adequate water seal at all times, to fulfill the purpose of

its installation. However, it should retain minimum quantity of water forits installation. However, it should retain minimum quantity of water for

this purpose.

2. It should be non-absorbent material.

3. It should be free from any inside projections, angles or contractions, so

that flow is not obstructed or retarded.

4. It should be simple in construction, cheap and readily available.

5. It should be self cleansing.

6. It should be provided with suitable access of cleaning.

7. Its internal and external surfaces should have smooth finish so that dirt

etc. does not stick to it.

Classification of traps:

(a) Classification according to shape

1. P-Trap- Resembles the shape of letter P, in which legs are right angle to

each other. See Fig. (a)

2. Q- trap or half-S-trap: Resembles the shape of letter Q. See Fig. (b)

3. S- trap: Resembles letter S, in which both the legs are parallel to each

other, discharging in the same direction. See Fig. (c). Fig (d) shows the

development of all the three types of traps.

(b) Classification according to use

1. Floor trap or nahni trap

2. Gully trap

3. Intercepting trap

1. Floor trap or nahni trap : Used to collect wash water from floors,

kitchens and bath rooms. It form the starting point of waste water floor.

It is made of cast iron, with a gravity at top, to exclude entry of solid

matter of big size. This cover can be removed to do frequent cleaning of

the trap. These traps have small water seal.