CHAPTER III

OPERATION AND MAINTENANCE OF WATER DISTRIBUTION NETWORK FOR URBAN WATER SUPPLY

A Maintenance system A pipeline maintenance system must ensure that all required maintenance work can be carried out with ease. The system is actually determined by the scale and type of facilities, the number of employees, and other aspects, but the system must also be able to cope with operation under both normal and emergency conditions. 1 Normal operation 1.1 Facility patrols and inspection Capital equipment and personnel qualified to conduct periodic patrols, inspections, servicing and surveys must be provided in order to prevent pipeline accidents from occurring. 1.2 Pipeline drawing preparation Pipeline drawings are essential for the maintenance of pipelines, and they must be absolutely correct because they are used on regular basis. This is why pipeline drawings must be prepared, and a system for their control must be established. 2 Emergency operations Pipeline leaks may cause flooding of homes, traffic accidents and traffic jams due to sunken roads, insufficient flow, and turbid water. In order to minimize such damage when a leak occurs, a system must be in place to initiate repairs immediately. As part of the system, it is a good idea to establish a stand-by system or an on-duty system organized into a cohesive unit that can respond in the event of an emergency. 3 Night and holiday dispatch A dispatch system must be established for nights and holidays since leaks can occur just as well outside business hours. In order to prepare for unexpected accidents, a mobilization plan must be set up ahead of time that designates essential restoration personnel and outlines notification arrangements so personnel can be summoned immediately and assigned to departments and sections. 4 On-call contractors In order for designated contractors to perform repair work, there must be a system of contractors, a method for designating emergencies, and annual contracts signed for handling accidents. An emergency call-out system must be established using a shift system that includes a number of companies, and a base must be set up with permanently stationed communications personnel to cope with unexpected accidents at any time, including nights and holidays.

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5 Emergency water supply Water wagons and portable cans must be prepared to provide emergency supplies to areas cut off from water. Coupling to distribution pipes in surrounding areas and neighbouring cities as well as other measures are highly desirable for providing immediate water supply assistance in order to keep the area cut off from water to an absolute minimum. 6 Equipment and repair material preparation Spare pipes for repairs organized by type and diameter as well as restoration machines and equipment must be kept in a constant state of readiness. In particular, a chart showing the amount of materials stored for emergency, a chart summarizing work equipment, an emergency mobilization plan and a work division chart must be prepared and inspected periodically each year. Ideally, materials stored for an emergency will be shared by neighbouring cities. Examples of work equipment include chain hoists, winches, pipe cutters, welding equipment, grinders, pipe work tools, service connection tools, and lighting equipment. 7 The Osaka Municipal Waterworks Bureau system 7.1. Maintenance office functions Construction site inspections on work by other utilities, such as gas lines, power lines and

telephone lines: Exposed pipeline protection inspections; Water pipeline leak and damage inspections; Leak repairs.

Pipeline facility repair: Pipeline leak detection and repair; Pipeline appurtenance repair; Test excavations for surveys.

Line patrols: Pipelines, pipe bridges, easements.

Sluice valve operation: Prior surveys (position checks, operating sluice valve checks); Operation (water shutoff, water flow, pipe flushing).

Pipeline appurtenance inspection: Sluice valve, air valve and fire hydrant inspection and servicing; Valve chamber inspection and, servicing.

Public notification: Water shutoff, turbid water occurrences, noise due to construction, construction

schedule plans. g) Patrol of construction sites along water lines. h) Surveys for pipe laying and positioning.

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Measurements of water pressure, flow rates and residual chlorine densities. j) Pipe flushing: Draining turbid water; Systematically flushing sediment deposits and scale deposits in the distribution pipes.

7.2 Number of staff

Maintenance office Eastern Western Southern Northern Total Office manager 1 1 1 1 4

Assistant manager 1 1 1 1 4 Executive engineers 3 3 3 3 12 Executive officers 1 1 1 1 4

Engineers 15 13 14 16 58 Clerical personnel 11 12 12 11 46

Pipe fitters 58 57 56 56 227

Drivers 4 3 4 4 15 Warehouse personnel 2 3 3 2 10

Delivery personnel 1 1 1 1 4 7.3 Number of vehicles owned Maintenance office Eastern Western Southern Northern Total

Pickup trucks 2 1 1 1 5 Trucks 3 3 3 3 12 Jeeps I 1; 1 I 4

Small vans 17 16 16 16 65

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7.4 Main equipment and tools

Maintenance office Eastern Western Southern Northern TotalFlowmeter 2 3 2 1 8

Water pressure gauge 10 15 11 11 47 Transceiver 8 6 6 7 27

Submergible pump 2 3 4 2 11

Drain pump 3 4 3 3 13 Generator 6 2 3 4 15

Pipe cutters 15 9 14 6 44 Water tank (1m3) 1 1 1 1 4

Plastic containers (10 litre) for emergency water supplies 27 20 37 15 99

Plastic containers (20 litre) for emergency water supplies 25 70 19 38 152

7.5 Materials stored for an emergency

Name of Material 075mm0350mm 0400mm01000mm

Straight pipe 1 each Fitting bend 45 4 each

22.5 4 each Collar 2 each 2 each

Flanged socket 1 each Flanged spigot 1 each

Double flanged pipe 2 each Gate valve 1 each

Fire hydrant Single-type 1 each Double-type I each

Flange packing 2 each Rubber gasket 8 each 4 each Retainer gland 8 each 4 each Bolt and nut 8 sets each 4 sets each Leak clamp 6 each 2 each

Split repair sleeve 3 each l each 7.6 Contractor agreements for repair work One of the following methods may be used for contracting repair work: Major non-emergency repair work. Regular contracted work agreement. Major emergency repair work. Only certain contractors are eligible, and these contractors

have first priority for this work. The contractor's agreement is concluded after work has been completed.

Minor repair work. Contracts are concluded per unit cost of the work type, such as excavation, backfilling, pipe laying, work on joints, steel sheet piling, concrete, etc.

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The procedures for minor repair work are as follows: Work per unit cost is contracted every six months. In the event of an accident, the Maintenance Office will dictate repairs to the

contractors. Engineers from the Maintenance Office will monitor the repair work and

prepare the records. Contracted companies will submit photos and repair reports as well as requests

for payment every two months. An inspector will compare the volume of work with the work records and

photographs, and will make sure that payment requests are in order. Payment will be made to the contracted companies for completed work. 7.7 System procedure for unexpected accidents One engineer, four pipe fitters and one driver will serve as on-duty emergency personnel at each Maintenance Office during the day and night all year around, including holidays, to handle unexpected accidents along pipelines. One of the repair companies contracted for minor repair work will always remain on call at night. The system ensures that someone will be on the scene of an accident within thirty minutes of receiving notification if an accident occurs anywhere in the city, so that accidents can be processed as quickly as possible. The trust of our citizens starts with quick repairs. B Line patrols There is a constant danger of leaks occurring because pipelines are exposed to various types of construction work, traffic loads, corrosion, uneven settling of the ground and earthquakes; and the pipes themselves suffer from ageing. Frequent leaks can have a major impact on the lives of citizens not only because of water shutoffs and reduced water flow, but roads and other underground facilities may be damaged or homes may be flooded. This is why it is so important to constantly patrol pipelines and inspect facilities in order to prevent leaks or to find them as quickly as possible. 1 Factors leading to leaks from pipeline facilities 1.1 Leaks from iron pipes Leaks from iron pipes are broadly classified as either cracks or corrosion. The main factors leading to cracks are unusual stresses and external damage, while most corrosion is caused by rust on the inner and outer surfaces. 1.1.1 Pipe cracks Grey cast iron is neither as strong nor as tough as ductile iron and it cannot withstand harsh laying environments, such as high traffic volume, so leaks do occur. Osaka City has been using ductile iron pipes for new installations and old pipe replacement ever since ductile iron was first developed, so the number of pipes cracking has decreased every year.

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Differences in the mechanical properties of ductile iron pipes and grey cast-iron pipes are shown in Table 3.1.

Table 3-1 Mechanical properties

Ductile iron pipe Grey cast-iron pipe Steel pipe

Tensile strength (N/mm2) min. 420 150 - 260 min. 400 Bending strength (N/mm2) min. 590 200 - 360 min. 400

Elongation (90) min. 10 Negligible min. 18 Modulus of elasticity

(N/mm2) 15-17 x 104 10-12 x 104 Approx. 20 x 104

Hardness (HB) max. 230 max. 230 Approx. 140 1.1.2 Pipe corrosion Damage to the coating on the outer surface of pipes during laying, as well as damage due to various types of constriction after laying, are two of the factors leading to corrosion. Corrosion gradually eats its way into the inner surface, and ultimately carbonizes the pipe. This type of corrosion reduces the strength of the pipe, and is a major factor in breaks and other damage. Some of the factors leading to corrosion in underground pipes are attributed to the effects of soil, such as the composition and non- uniformity, as well as the electrical resistance, aeration, pH levels, dissolved salt content and bacterial activity. When pipes are laid in corrosive soil areas, using the polyethylene-sleeving corrosion-protection method is recommended. In the polyethylene-sleeve encasement method, the entire length of the pipeline is covered with a 0.2mm thick polyethylene sleeve on site. These polyethylene sleeves prevent direct contact between the soil and the pipes, even though the polyethylene film does not adhere to the surface of the pipe. Even if a polyethylene sleeve is damaged and ground water enters the gap between the sleeve and the pipe, such water remains stagnant and unable to move. Then the depolarizers, such as oxygen, are consumed and, as a result, corrosion is suppressed. With regard to the polyethylene sleeve standards, national standards such as BS6076 and ANSI/AWWA C105 are popular. Recently, the polyethylene sleeve has also been standardized in ISO 8180. Corrosion from the inner pipe surface is caused by rust forming in iron pipes that are not internally lined and the rust may, in some cases, markedly reduce the fundamental water flow capacity of the pipe. The rust is not only a factor leading to leaks caused by cracking because the strength of the pipe is reduced by pipe carbonization, but rust effluent is a factor leading to turbidity in tap water.

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Figure 3.1 Polyethylene sleeve encasement methods

1.1.3 Leaks from joints Until 1955, iron pipes were joined by hemp yarn and lead. One of the drawbacks of this type of joint was that joint sections were easily loosened by vibrations, such as traffic loads and earthquakes, so that if recaulking the lead on joint sections every time a leak occurred was inadequate, leak prevention fittings had to be attached in addition to the caulking. Around 1955, a mechanical joint that offset the drawbacks of lead joints and offered both superior installation and leak prevention characteristics was developed. Osaka City used pipes with the mechanical joint for new installations when existing pipes were replaced. This effectively resulted in fewer leaks from joint sections in iron pipes every year. These new connecting methods take advantage of the elasticity of rubber. Generally, loosening and slippage are prevented by bolting the rubber in place. Maintenance on the pipelines should not be overlooked, however, because rubber degrades, bolts come loose, and there is a danger that the pipes will disconnect if vibrations from road works and the ever-increasing traffic volume continue for a long period of time.

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Figure 3.2 Mechanical joint 1.2 Leaks from steel pipes The features of steel pipes are the basic characteristics of steel, i.e. strength, and full integration through welding. Like the joint sections in iron pipes, leaks from steel pipes may be generated in the expansion joint installed to absorb pipe expansion and contraction caused by earthquakes and temperature fluctuations. When leaks are generated by corrosion of the steel pipe, electrolytic corrosion is often the key factor leading to the leak. This is because steel pipes, which form a continuous tube welded together by joint sections, are excellent conductors, and thus are highly susceptible to electrolytic corrosion caused by stray current in the ground. Therefore, measures for cathodic protection must be implemented for the particular pipe-laying environment, such as under electric train tracks and near high-voltage power cables. Pinhole corrosion due to improper coating causes some leaks. Other leaks on exposed pipelines, such as pipe bridges, are caused by advanced corrosion as the coating deteriorates due to progressive oxidation caused by rain or temperature fluctuations connected with seasonal changes. Therefore, periodic repainting of the exposed steel pipes before the onset of advanced corrosion due to coating deterioration is essential for extending the service life of pipes. 1.3 Leaks from asbestos cement pipes Asbestos cement pipes are made by adding asbestos fibres to water mixed with cement and quartz sand, prior to curing in water and treatment by autoclave curing. The pipes are lightweight, resistant to corrosion, and generate neither electrolytic corrosion nor rust tubercles because the pipes are non-metallic and are not subject to reduced water flow capacity. On the down side, the pipes have less shearing strength than either iron or steel pipes, so they often leak because of breaks and cracks. There has been tremendous interest in recent years in using asbestos cement pipes for water pipelines as a result of growing concerns about asbestos being carcinogenic when used as a building material. Unlike asbestos fibres that disperse into the air, very little asbestos fibre dissolves into water from water pipes, so the pipes are considered relatively safe for now.

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1.4 Leaks from plastic pipes Plastic pipes are lightweight and inexpensive, they resist corrosion and rust, and they are easy to install. These pipes, however, have relatively low resistance to external shocks and heat, and volatile liquids such as thinner can seep through the pipes with relative ease. Ultraviolet rays also break down the plastic pipes when the pipes are exposed. These drawbacks should be kept in mind when using plastic pipes. Plastic pipes are connected with either a bonding agent or with rubber rings. 2 Line patrols The most basic maintenance of pipelines will be a line patrol carried out periodically by the staff concerned. Preventive maintenance is particularly, important for pipelines, to detect any problems in advance and hence avoid serious damage. Preventive maintenance is based in principle on three senses: walk, look and touch. Line patrols must be implemented systematically based on a set implementation programme. At the same time, some type of system must be set up to deal quickly and appropriately with a situation deemed abnormal. 2.1 Equipment carried along for patrols Pipeline drawings (1/3000 and 1/1000); Measuring tape; Inspection report sheets. 2.2 Patrol targets Underground pipelines; Patrols should pay particular attention to trunk pipelines, pipelines where leaks

frequently occur, and pipelines buried along main roads; Pipe bridges; Pipeline easements; Construction sites for other utilities.

2.3 Frequency of patrols Patrols should be initiated whenever required, and they should check for damage especially immediately after heavy rains or earthquakes. 3 Underground pipelines 3.1 Details of tasks 3.1.1 Presence of leaks If roads are wet or the cracks in the pavement are moist, even though it has not rained or water has not been sprinkled on them, there is a possibility of a leak. Apparently, there does not seem to be any imminent danger in the case of such leaks, but water storing up under the pavement may sometimes be creating empty spaces so moisture could be a prelude to a street cave-in.

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3.1.2 Presence of dips or cave-ins on roads above pipelines or in neighbouring areas When an underground leak occurs, earth and sand in the surrounding area may be washed away, or the earth and sand may be compacted by the water to form an empty space underground. This type of situation most often occurs when sand is used for backfilling. Even if an empty space develops under paved roads, the road is supported solely by the strength of the pavement at first. But the road eventually gives way under its own weight and the weight of vehicular traffic, and it starts to sink. Roads with heavy vehicular or crowded foot traffic may sink just as a heavy vehicle passes over, and thus pose the very real danger of pedestrian and other accidents.

Figure 3.3 Road cave-in 3.1.3 Water flowing into manholes

Since various lines and facilities for other utilities, such as electricity, telephones, water and sewer lines, are laid under roads, manholes are installed at regular intervals in order to service those lines and facilities. When manholes are opened for inspections or construction work, water may be flowing out from the cracks in the side walls, or may be brought from other lines to form standing water, and leaks from water pipes should be the first consideration in most of these cases. There are times when leaking water is brought from a long way away, and inspecting the manhole on the upstream side of the water flow with the cooperation of the utility companies concerned is required. In some cases, more detailed surveys based on pipeline drawings may be imperative. Water seeping into pipes from the joints of sewer pipes is often discovered with sewer lines. Exceptionally heavy rains and underground water may also be the cause, but often the blame can be laid on leaks, so surveys on leaks from inside sewer manholes are very important. When U gutters and street gullies are installed on both sides of a road, just rain water or general waste water from households and factories normally flow into the U gutters and street gullies. But if surprisingly clear water can be seen flowing in when the cover to the street gully is lifted, then there is a high probability that the water is leaking from service lines. This is a key point in discovering leaks during U gutter and street gully surveys.

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Figure 3.4 Leakage flowing into manhole 3.2 Handling Check for the presence of leaks if any signs of leakage or any abnormalities are found along the pipelines. Repairs should begin immediately if it is determined that there is a leak. The strength of patrols comes from observation and attentiveness

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Table 3.2 Line patrol inspection report

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4 Pipe bridges and bridge-attached pipes When water pipelines have to traverse rivers and other natural obstacles, often pipe bridges are installed, or pipes are attached to road overpasses. Maintenance on water pipelines in such locations is not very easy, so it tends to be overlooked. Attached pipes are, along with the overpass, constantly subjected to vibrations from vehicular traffic, while the pipe bridges are constantly subjected to wind and direct sunlight. Both types of pipe are directly exposed to variations in the ambient temperature, and therefore have to cope with much more severe conditions than underground pipes. As a result, there is a very high risk of leaks because the pipe itself tends to corrode due to the coating breaking down and peeling, and joints tend to loosen due to vibrations and other factors. Pipe sections that are attached to bridge abutments often leak at the joints of the pipes because of differential settlement at the boundary between the ground and the bridge abutments, and water sometimes runs from the bridge abutment into the river. 4.1 Details of tasks Superstructures: Check water leakage from pipes, air valves and expansion joints. Check that the structures are not rusted.

Substructures: Check for settling, sloping, and cracks in the concrete. Survey whether every anchor bolt is fastened tightly against every concrete base

(whether there is no loose anchor nut). Survey whether any excessive scouring/corrosion by river water flowing around

abutments and/or piers. 4.2 Handling Initiate repairs immediately if there is a leak. If rust is observed, repaint every structure with designated paint after removal of any

rust. With other types of damage, initiate repairs if the damage is prominent. Pipe bridges are the only pipeline installations clearly visible to the outside world.

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Table 3.3 Pipe bridge inspection chart

Pipe bridge no. Inspection month/day/year Name of pipe bridge

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5 Pipeline easements Table 3.4 shows the details of tasks for pipeline easements.

Table 3.4 Details of tasks for pipeline easements

Details of tasks Handling Check whether boundary posts are damaged, missing, sunken or moved. Restore posts to their original condition.

Check whether boundary fences, signs or gates are damaged. Repair or replace with stronger materials.

Check whether the land is overgrown with weeds. Mow the weeds.

Check whether dirt, sand or garbage is being dumped illegally on the land.

Remove the dirt, sand or garbage. Install fences and signs along the boundary, and notify the public.

Check whether the land is occupied illegally.

Remove all illegal objects, negotiate with the occupiers, and remove any possessions.

6 Construction site for other utilities Whenever there is construction work such as sewer, gas, electricity, telephone or building construction near water pipelines or that will expose pipes, patrol inspections must be implemented to check whether there are any adverse effects on the pipeline, and every effort must be made to prevent leaks before they happen. The most important point with construction work by other utilities is to get information about the construction work as soon as possible, to hold a sufficient number of meetings prior to the start of construction, and to thoroughly check the positions of pipelines at the construction site. In order to carry these out most effectively, it is best to keep pipeline drawings organized at all times, and to hold information meetings with each of the utilities involved. Figure 3.5 Damage due to construction work by other utilities

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6.1 Details of tasks 6.1.1 Prior to the start of construction Exchange agendas with the contractor, and verify details. Make the contractor submit contact numbers and addresses in case of an emergency. Require the contractor to do test excavations to verify the precise position of pipelines. Require the contractor to mark pipe positions, openings and depths with paint on

roads. Require the contractor to drill observation shafts in order to measure the amount of

pipe settling. Check whether valves and fire hydrants will be available for use as usual. (Marked

with paint.) 6.1.2 During excavation Check whether the contractor is confirming the pipe position by excavating to expose

the top of pipes before installing piles or sheet piles. Check whether there is sufficient distance between the pipes and the piles or sheet

piles (50cm or more as a rule). Check whether to use manual labourers for excavation when pipe will be exposed. Check, whether gushing water or sand will flow out from gaps between the sheet piles. Check whether the road surface behind the sheet pile is not settling. 6.1.3 When pipes are exposed Check whether water is leaking from the pipes. Paint all joints, and check whether any are disconnected. Check whether restraining equipment or steel reinforcement is set perfectly to prevent

pipe fittings from disjointing. Check whether the pipeline can cope with expansion and settling by using expansion-

flexible joints. Check pipe suspension structures: Are special beams used to secure suspension fittings? Are steel sheets and iron bolts used for suspension fittings? (Wire rope need not be

used.) Is a turnbuckle mounted to adjust the suspension fitting for expansion? Is the spacing between suspension fittings too wide?

Nominal diameter Space between suspension fittings

350mm max. 2.0m max.

400mm min. 1.5m max.

Are steel support beams installed under heavy appurtenances, such as gate and

butterfly valves?

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Check the spacing between water pipes and other underground pipes: Locations where water pipes run parallel to other underground pipes.

Nominal diameter Space from other underground pipes

450mm max. 30cm min.

500mm min. 50cm min.

Locations where water pipes intersect other underground pipes.

Nominal diameter Separation from other underground pipes

450mm max. 30cm min.

500mm min., without joints 30cm min.

500mm min., with joints 50cm min.

Locations with appurtenances such as gate and butterfly valves: Separation from other underground pipes should be at least 50cm.

6.1.4 When backfilling Check whether the backfilling earth is good quality earth. Check whether the backfilling earth under and around the pipes is adequately

compacted by rolling compaction or other methods. Check whether the sheet piles are pulled out after the backfilling is adequately

compacted. Check whether the valve chamber is properly restored. Check whether the iron cover on the valve chamber has been buried after backfilling.

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Table 3.5 Survey chart for sluice and other valves

C Leakage control work Leaving pipes leaking wastes clean water that has gone through intake and treatment processes at great expense. This is not only an economic loss, but can also be the cause of poor water supply quality and city water pollution as well as secondary disasters, such as traffic accidents due to road cave-ins. These are some of the reasons why it is so important to prevent leaks. The demand for water today is growing in nearly every city in the world, but increasing water supplies entails significant problems related to developing water resources. In some areas, moreover, the water resources themselves are critically insufficient. From this standpoint, it is also crucially important that we prevent water leaks in order to make more efficient use of existing water resources. Leaks are broadly classified as either above-ground or underground leaks. Above-ground leaks are leaks generated in the ground which then appear on the ground, as opposed to underground leaks that are also generated in the ground, but never appear on the ground. Leaks must be prevented before they occur, and those that already exist must be detected and repaired as quickly as possible. Since above-ground leaks can be seen, they are easy to find and can generally be repaired in a very short time. Underground leaks, on the other hand, cannot be found without special surveys, so it takes a long time from the minute the leak is discovered until it is actually repaired. The volume of water lost is therefore tremendous. A leak left alone tends to increase on its own. This is why it is so important to detect and repair underground leaks on an ongoing basis, and how efficiently underground leaks are detected is critical to leakage control overall. 1 Analysis of distributed water volume 1.1 Purpose of analysis The distributed water volume is the amount of water transmitted into water supply areas through the main distribution pipes from the service reservoirs. The water volume is measured and recorded by a flowmeter installed at the starting point of the main distribution pipe. Distributed water volume analysis looks at how the distributed water volume is consumed by specific items. When establishing leakage control policy, first of all it is important to analyse the distributed water volume in the organization and grasp the current status of water use and leakage, to analyse the effects of leakage control measures and to select the most effective method. In Japan, distributed water volume is analysed according to Table 3.6 by the directive of the Ministry of Health and Welfare. The statistics in the table are 1992 figures for Osaka City.

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Table 3.6 Distributed water volume analysis

Authorized water use

521,125,829m3(92.04%)

Accounted water volume

491,298,393m3(86.77%)

Unauthorized water use

45,085,371m3(7.96%)

Unaccounted water volume 29,827,436m3

(5.27%)

Metered water volume 477,341,295m3 (84.30%)

Sub-distribution volume 13,754,503m3 (2.43%)

Others 202,595m3 (0.04%)

Unmetered consumption 26,328,821m3 (4.65%)

Utility water use 3,498,615m3 (0.62%)

Selected reduced price water volume 3,788,512m3 (0.67%)

Amount of leakage, unexplained water volume 41,296,859m3 (7.29%)

Distributed water volume

566,211,200m3(100.00%)

1.2 Terminology, definitions and explanations Distributed water: This refers to the total volume of water flow (transit volume) at

the starting point of distributed pipelines. The starting point of distributed pipelines refers to the point at which distributed pipelines branch off from the outlet of a distribution reservoir, a distribution pump station, or from transmission pipelines. In order to measure distributed water volume, a flowmeter must be installed at the starting point.

Authorized water use: This refers to the water volume which provides income and

the water volume authorized for use in the water supply business. Account water volume: This refers to the water volume that provides income from

water rates or from other public accounts. Water volume charged for water rates: This refers to the water volume based on

water rate collection. Where a meter is installed on the service line (meterage connection), it refers to the actual metered volume of water used, but where no meter is installed on the service line (flat rate connection), it refers to the volume obtained by multiplying the basic water consumption by the number of taps or users.

Sub-distribution volume: This refers to the water volume sub-distributed to other

water supply organizations, and the rate for the water volume is collected from them. Others: This refers to the water volume that provides income from other public

accounts, such as water for public parks, water for public restrooms and fire-fighting water.

The water volumes described above must be accurately obtained from reports received from affiliated companies. Unaccounted water: This refers to water volumes that do not provide income for

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consumption. Unmetered water volume: Even though consumption is authorized, this refers to

water volume that cannot be charged for due to the insensitivity of meters at individual connections.

Meters in general use have an appropriate or proper flow rate range, depending on the type of meter, because of their mechanisms. Outside that range we cannot expect an accurate flow rate and the difference grows between the actual flow rate through the meter and the measured flow rate. In such circumstances, the measured flow rate is usually lower than the actual flow rate. This difference is the unmetered consumption, and is characteristic of each meter, so it differs according to the type of meter, the pipe diameter, and the age of the meter. Selecting the proper meter diameter according to actual flow rate is crucial, and the meter must be installed according to standard installation procedures. Use of meters where either of the above was not done correctly aggravates unmetered consumption. Since it is impossible to actually measure unmetered consumption for every meter installed, generally some meters are selected at random and their unmetered consumption is measured. Utility water use: This refers to the water volume used in the maintenance activities

required for distribution facilities, such as water for leakage control work as well as water for flushing distribution and service lines.

Unauthorized water volume: This refers to any water volume not authorized for use. Selected reduced price water volume: This refers to the amount of water released

because of turbidity, repairs or other reasons, and targeted for reduced pricing by an adjustment in water rate charging.

Leakage: This refers to the amount of water that leaks from service lines upstream

from the meter and from distribution pipelines downstream from the flowmeter. Unexplained water volume: This refers to the remainder after subtracting the sum of

the above items from the distributed water volume. When the ratio of individual water volume types to the distributed water volume is expressed as a percentage (%), we get the following: Authorized rate (%) = authorized water volume/distributed water volume x 100 Unauthorized rate (%) = unauthorized water volume/distributed water volume x 100 Account rate (%) = account water volume/distributed water volume x 100 Leak rate (%) = leakage/distributed water volume x 100

1.3 Errors for individual water volume type The unexplained water volume is the accumulated measurement errors for individual water volume types. Special attention must be given to the following points in order to reduce these accumulative errors. Measurement errors in distributed water volume: The metering error of

flowmeters becomes more difficult to measure as the scale of the distributed water volume increases. It is possible to measure the metering error, for example, by comparing the value calculated from variations in the water level of the service

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reservoir to the value measured by the flowmeter in order to compensate for the flowmeter error.

Calculation error for the water volume for flat rate connection: It is desirable to

shift flat rate connections to meterage connections by installing a meter. In Osaka City, all service connections are meterage connections.

Recognized error in water volume for public use: Meters should be installed for

water used in public facilities, such as public parks and public restrooms. It is also important to set a calculated standard to get a precise understanding of the amount of water used for fire fighting. In Osaka City, flowmeters are being installed in all fire-fighting vehicles, and in all public parks and public restrooms.

Recognized error in unmetered water volume: There are multifarious use

conditions for service installations, so it is important to select and use the proper water meter for each type of service installation. It is also necessary to manage and maintain meters to facilitate meter reading and replacement. Moreover, it is important to bear in mind that careless installation of meters is directly related to unmetered water volume and failure soon after installation.

Recognized error in utility water use: With water used for business, such as flushing

turbid water and cleaning pipes, closely following water pipeline construction, standards must be prepared for the calculation method as well as the confirmation method for on-site water use volumes in order to obtain accurate data.

Recognized error in settled reduced price water volume: When damage or other

problems with a water meter make it impossible to measure the consumption, the use conditions must be surveyed, and as accurate a water volume as possible must be estimated.

Unexplained water volume: During meter inspections, bill collections and leakage

control work, every effort must be made to find and prevent illegal service connections, such as service lines that are connected without permission as well as unlawfully laid service lines that do not run through a meter.

2 Leakage control 2.1 Proposing implementation plans 2.1.1 Selecting work or implementation areas The first step in an implementation plan is to select work or implementation areas on a priority basis. In urbanized areas, underground leaks generally tend to occur most often in the following locations: Paved roadways; Areas with sewer lines installed; Places where the underground water level is high; Places where the ground is mostly sand or gravel.

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Areas with frequent above-ground leaks also tend to have frequent underground leaks. Therefore, the following points must be considered by individual areas when selecting a work or implementation site. Number of leak repairs in the past; When the pipes were laid; Depth of the underground water level; Current status of sewer line installations. 2.1.2 Establishing the work cycle Even though an underground leak may be repaired once, new leaks can appear with the passage of time, and small leaks will eventually expand over time. This phenomenon is known as leak restoration. With implementation plans for leakage control, determining the average work cycle is a critical part of the plan. Work areas with high account rates, areas with excellent water supply conditions, and areas with high leakage control costs are served more economically by longer work cycles. Work areas that tend to have insufficient flow or that tend to have high rates of leak increases are more economically served by shorter work cycles.

Figure 3.6 Leakage restoration We generally see the following relationship when it comes to work cycles and the cost of leakage control. As the work cycle gets longer, the cost of leakage control decreases because the work length per year is less, but leakage increases over the period. Conversely, as the work cycle gets shorter, the cost of leakage control increases because the work length per year is longer, but leakage decreases over the period. Therefore, the most economical work cycle is when the sum total of the cost of leakage control and the cost of leak losses is lowest.

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Figure 3.7 Cost of leakage control and the cost of leak losses The following is a calculation method for determining the most economical work cycle. First, the relationship between the work cycle and the cost of leakage control is expressed as follows: X: Cost of leakage control (yen) in one year when the work cycle is n (years). L: Length of distribution pipes (km) targeted in the leakage control. n: Work cycle (years). A: Cost of leakage control per kilometre of pipe (yen/km). A1: Cost of leak surveys per kilometre of pipe (yen/km). A2: Cost of leak repairs per kilometre of pipe (yen/km). a: Cost of repairs for the number of new leak locations generated in one year per kilometre of pipe (yen/km). Next, the relationship between the work cycle and the cost of leak losses is expressed as follows: Q: Cost of leak losses (yen) in one year when the work cycle is n. S: Unit cost of leakage (yen/m3).

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q: Leakage per kilometre of pipe that remains even after leak prevention work (m3/day/km). r: Newly generated leakage in one year per kilometre of pipe (m3/day/km). Since the most economical work cycle is n when X+ Q is at its minimum: The work cycle obtained from the above calculations comprises a full round to each successive work area, but the use of the equations is strictly limited to leakage control work targeting naturally increasing leakage. Individual figures used in the equations may vary tremendously depending on conditions, so it is difficult to rely on the accuracy of the calculated results. Because of this, setting the average work cycle within four to five years, or two years particularly in critical districts, is highly recommended. Leaks cause costs (required expenditures) and effects (economic effects). 2.2 Work procedure for leakage control The work procedures for leakage control are as follows: Designing a work zone. Investigating and servicing pipeline appurtenances. Measuring the zone leakage prior to starting detection work. Detecting leak locations. Repairing leak locations. Measuring the zone leakage after repair work has been completed. Organizing after work has been completed. 2.2.1 Designing the work zone A work zone is the work unit for leakage control, and an appropriate size for each work unit is set based on pipeline drawings. The size of a work zone is determined by the distribution pipeline network, the number of service line branches, the position of sluice valves, the accuracy of the leakage measurement, and the work efficiency. Generally zones are set so that one zone covers a 13 kilometre distribution pipeline. Installing sluice valves when required is a good way to decrease the size of work zones. 2.2.2 Inspecting and servicing pipeline appurtenances 2.2.2.1 Verifying site details against the drawings Inspect the current status of pipelines and appurtenances within a work zone through pipeline drawings and ledgers for pipeline appurtenances. To verify actual site details against the drawings, confirm the exact locations of pipelines, sluice valves, fire hydrants and other appurtenances, and obtain actual measurements about distribution pipe length and other details. If there is anything unclear, excavate to search for it.

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2.2.2.2 Inspecting service installations Inspect all service installations, conduct functional surveys on all curb stops at every house connection, and service malfunctioning equipment. 2.2.2.3 Functional inspection of sluice valves and fire hydrants Inspect sluice valve functions in order to block the work zone, and service so that the water can be completely shut off. Fire hydrants should also be surveyed for leaks, and serviced. Repair or replace unusable equipment. 2.2.2.4 Checking water shutoff work Check sluice valve operating procedures for blocking the work zone to measure the zone leakage. Be sure to notify water users, fire stations and others affected before the day that the water is shut off. 2.2.3 Zone leakage measuring prior to starting detection work The direct and indirect measuring methods are the two means available for measuring leakage. 2.2.3.1 Direct measuring method The procedures for this method are as follows: Use a hose to connect a fire hydrant outside the work zone to one inside the work

zone, and install a flowmeter and a water pressure gauge between the two hydrants. Completely block the work zone with a sluice valve. Completely close the curb stops for all service lines in the work zone. After verifying that there is no water use, measure the water volume flowing into the

zone from outside the work zone with a flowmeter. This is the leak water volume. The flow rate should be measured in 13 minute intervals, and the measuring time should be at least 30 minutes without noticeable fluctuations in the flow rate.

One of the advantages of this method is that the measuring accuracy is extremely high because all curb stops in the work zone are closed. The disadvantage is that closing and opening all the curb stops requires a significant amount of time and labour.

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Figure 3.8 Method for measuring leakage in a zone

2.2.3.2 Indirect measuring method When the curb stops are not closed in the procedures above, the water volume that flows into the zone from outside the work zone is the sum of the used water volume and the leakage. Measured flow rate = leakage + used water volume Here, if the flow rate is measured while absolutely no water is being used in the work zone, then the measured flow rate is just the leakage. During the mid-night hours (1am to 4am), when the volume of water used is low, these periods may be designated periods without water use even though the time is short, and the measured flow rate at this time is also referred to as the leakage: In the indirect measuring method, the minimum flow measured during these mid-night hours is regarded as the leakage. The work procedures for this type of measurement are as follows: Use a hose to connect a fire hydrant outside the work zone to one inside the work

zone, and install a flowmeter and a water pressure gauge between the two hydrants. Completely block the work zone with a sluice valve. Measure the water volume flowing into the zone from outside the work zone with a

flowmeter. The minimum flow measured is the leakage. In general, the measuring time should be at least one hour.

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Figure 3.9 Periods with no water use The advantages of this method are that the work involved in servicing and closing the curb stops is eliminated, and that measurements can be taken without confusing users about water shutoffs. The disadvantage is that the measurement may actually include water use, so this procedure is not as accurate as the direct measuring method. Since there is some long-term water use even during these mid-night hours because there are large-volume users, such as those who have receiving tanks in the work zone, the accuracy of this method can be improved somewhat by closing the curb stops of such users before taking the measurement, with prior notice to the users. Generally, when measuring the minimum night flow in small work zones (few service line branches, low population in the work zone), there are many periods with absolutely no water use, and long continuous periods without use, but as the work zone becomes larger, there is less time with absolutely no water use, and continuous periods without use are extremely short. It must also be remembered that the frequency of periods with absolutely no water use, as well as continuous periods without use, varies depending on the character of the work zone (whether it is a residential or commercial area). A highly accurate meter must be used when taking flow measurements in zones with short continuous periods with absolutely no water use.

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Figure 3.10 Opening and closing the curb stops of large-volume users 2.2.3.3 Leakage conversion for water pressure The results obtained by measuring leakage are actually leakage in terms of water pressure at the time of measurement. Since water pressure varies with the season and time of day, estimating the actual leakage involves surveying the average water pressure in the area being measured, and then converting the leakage corresponding to that pressure. Normally measured leakage is collected, and is treated as a statistical volume, so if an appropriate standard water pressure is set, the leakage is converted in terms of the standard water pressure, and is written down with the leakage at the time of measurement. This information can then serve as data that is both reproducible and universal. In Osaka City, the standard water pressure is set at 2.0kg/cm2. The following equation is used to convert leakage for water pressure: Q0: Leakage at the time of measurement. Q: Converted leakage. P0: Water pressure at the time of measurement. P: Standard water pressure. The exponent r is one of the following: r = 0.5: This figure is used when it is assumed that the leak hole is an orifice.

Experiments have indicated values very close to this for individual leaks. r = 1.0: This figure is used when it is assumed that gaskets in the joint section or

cracks in the pipe are leaking into the surrounding soil.

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The current status of the leak determines which of these two figures will be used. 2.2.4 Detecting leak locations The detection of leak locations involves primarily placing a sound-listening stick in direct contact with objects, such as sluice valves, fire hydrants, air valves, curb stops and meters. Check for leaks by touching the other side of the listening stick to your ear to discern leak noise from the complex range of noises generated above and under the ground. This basic method has not changed in the years since leak detections were first instituted, and it is still used today to detect leak locations. The detection does require a certain amount of training. As far as actual leak noise is concerned, outflowing noise that scrapes against pipe walls when water is flowing out from pipes, or impact noise that occurs when water strikes various soils surrounding the pipe, are intricately formed and reach the ground level by propagating through a medium, such as earth and sand. The frequency of the noise varies widely depending on the conditions, such as peripheral soil, pavement types, piping materials and the ground's ability to cut off water. Non-metallic pipes in particular are not as good at propagating leak noise as metallic pipes, so such pipes do not facilitate detection of leak locations with an acoustic leak detector. In addition to the noises above, flowing water noise in pipes, traffic noise and other noises, such as vibrations, that are similar to leak noise are constantly present and often hinder listening. Depending on the circumstances, conducting detection at night may be more effective in areas where traffic and urban noise hinder acoustic detection. The detection of leaking water entails attentiveness and a desire to succeed.

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Figure 3.11 Sound listening stick

Figure 3.12 Acoustic detection for leak locating with the listening stick

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2.2.4.1. Characteristics of leak noise Propagating distance of leak noise: The propagating distance of leak noise in

pipeline has tendencies as shown in Table 3.7. Table 3.7 Propagating tendencies of leak noise

Pipes with long propagating distances Pipes with short propagating distances

Small diameter pipes Large diameter pipes

Cast iron pipes, steel pipes, asbestos cement pipes, lead pipes, stainless steel pipes

Polyethylene pipes, plastic pipes

New pipes (pipes with no scaling or corrosion) Old pipes (pipes with heavy scaling and corrosion)

Welding joints, lead connecting joints Joints that use rubber gaskets

Low-pitched leak noise High-pitched leak noise

Acoustic characteristics of leak noise: Table 3.8 shows the general relationship of

leak noise categories that can be heard. Table 3.8 The relationship of high- and low-pitch leak noise to various conditions

High-pitched noise Low-pitched noise

Small leak holes Large leak holes

Complex leak hole shapes Simple leak hole shapes

Fast flow through the leak hole Slow flow through the leak hole

Small diameter pipes Large diameter pipes

Steel and stainless steel pipes Cast iron, asbestos cement, plastic and polyethylene pipes

Short distance Long distance

High water pressure Low water pressure

False leak noise: The problem with detecting leaks using the acoustic detection

method is that there are false sounds, such as noise and extraneous sounds that closely resemble leak noise. In terms of how noise is generated, false leak noise is continuously generated by a variety of noise sources, such as water flowing through pipes, tap water use, circuit noise inducted from power cables, exciter frequency noise constantly generated by electric transformers and fluorescent lights, motor noise and wind noise if the wind speed is 4 metres per second or faster. When these types of noises are propagated through the air and ground, there is a real danger that they will be mistaken for leak noise. This is why it is so important to get a good understanding beforehand of the characteristics of the noises that closely resemble leak noise: The sound of flowing water in pipes. The scraping sound generated when

flowing water passes through pipes or passes around obstacles in the gate valve is propagated through water and pipe walls as a vibrational sound. When a gate valve is not fully opened, the scraping sound of flowing water can in no way be distinguished from leak noise. These scraping sounds are a hindrance to acoustic leak detection.

Circuit noise, such as power cables. Power cables laid underground, transformers on poles, street lights and other such equipment generate low-

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frequency noise through inductive current and exciter vibrations, which mean that special care must be taken when listening anywhere near such facilities.

Water tap noise. Water tap noise is generated when large volumes of water are in use. Special care must be taken here because it is quite easy to mistake this sound for leak noise when acoustic leak detection is conducted on pipelines. The sound of water tap use can be distinguished by closing and opening the curb stop.

Flowing sewage and dripping noise in manholes. Flowing sewage and dripping noise in manholes sound very much like leak noise, but the dripping sound characteristic of surface water as well as a heavy reverberating noise can be faintly heard. Special care must be taken here when conducting acoustic leak detection.

Traffic noise. Traffic noise is transitory and the volume of the noise varies irregularly, so this type of noise is quite easy to distinguish. However, the scraping sound of tyres at least 60 metres away can easily be mistaken for leak noise, so special care should be taken here in acoustic leak detection.

Wind shear noise. A low-frequency wind shear noise is generated if the wind is blowing during acoustic leak detection, and this may well be mistaken for leak noise. If the wind speed is 46 metres per second (can be felt on the skin), wind shear noise becomes continuous, and sounds most like leak noise, so it is the most difficult to distinguish. At wind speeds higher than those listed above, leak noise cannot be heard at all.

Urban noise. Urban noise is a combination of various noises, such as wind, building cooling and heating equipment as well as traffic, which forms in the valleys created by tall buildings. The frequency components of this noise cover a broad spectrum, and may hinder listening surveys because they include a frequency component very close to that of leak noise.

Tremendous time and effort are required to detect leaks, so let's try to repair them as quickly as possible.

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2.2.5 Leakage flow rate The leakage flow rate is measured with a beaker and ladle, and is assumed from the current drain status of the drain pump (capacity, number of rotations, operating times). Significant training is required to eliminate subjective individual differences in the measurements. If the leakage measured in the zone leakage measurement prior to starting detection work is close to the total leakage metered individually at the time of repair, then it can be supposed that all leaks in the zone or in the pipeline have been repaired, and the leakage measurement after the repair work has been completed can therefore be eliminated.

Table 3.9 Leakage measuring for 13mm service pipes When there is drip

No. of drips per minute 5 10 30 50 70 100 150 200

Leakage (ml/min) 1.3 2.3 7.0 11 16 23 31 43

When there is continuous flow 2.2.6 Measuring zone leakage after repair work has been completed Zone leakage is measured again after detection and repairs on leak locations have been completed in order to determine the effectiveness of work that has been done. Here every effort should be made to prevent leaks, but setting zero as the goal for leakage in actual works requires significant expenditures and labour, and so is not very economical. There are times when a certain amount of leakage is unavoidable in terms of economics and technology. Here we will talk about the concept of unavoidable leakage as a work target. It is impossible to set a uniform figure for unavoidable leakage, but generally a standard is set for the average leak density for all supply areas. The work procedure is the same as the one for the zone leakage measurements prior to starting work, and a zone passes if leakage is below the unavoidable leak level. If leakage exceeds unavoidable leakage, then detect and repair operations are instituted again. 2.2.7 Organization after work has been completed Work reports are prepared and pipeline drawings as well as appurtenance ledgers are revised once the leakage control work has been completed. An example of the form used for work reports is shown in Table 3.10.

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Table 3.10 Report on implemented leakage control work

ANNEX III

CHANGE IN LEAKAGE CONTROL MEASURES IN OSAKA

MUNICIPAL WATER WORKS BUREAU A Leakage control measures taken by Osaka Municipal Water Works Bureau Figure 3.13 shows the change in leak rate in Osaka City. Before 1944, there was no correct statistical data concerning leak rate, but the waste-water volume was 25% to 29% of supplied water volume, meaning that no special measures were taken to control leakage. In 1945, leakage control measures were taken for the first time because the estimated leak rate had reached 70% due to war damage. In the early stages, the leak rate dropped rapidly with the implementation of leakage control measures, but after that it decreased only gradually. At present, the leak rate is about 7%. In this period, leakage control measures were changed several times, thereby affecting the leak rate. Table 3.11 shows the changes in leakage control measures. From 1945 to 1946, temporary leakage control measures were taken for urgent pipe repairs in heavily damaged areas. However, from 1947 the focus switched to systematic leakage control. From 1952, the work area of systematic leakage control was expanded to the entire city and the work began to be implemented cyclically.

Table 3.11 Changes in leakage control measures Time Measures Leak Rate (%) 1945 Temporary Leakage Control 70 1947 Systematic Leakage Control (Specified Area) 51 1952 Systematic- Leakage Control (Entire City) 31 1960 Service line Improvements 24 1965 Distribution Main Improvements 20 1991 Discontinuance of Systematic Leakage Control 7

On the other hand, service line improvements were commenced in 1960 and distribution main improvements were commenced in 19.65, as other preventative measures against leakage. The combination of systematic leakage control measures and facility improvements were able to reduce the leak rate to less than 10%. However the low leak rate caused low cost efficiency in systematic leakage control. Accordingly, systematic leakage control was discontinued in 1991. B Details of each control measure 1 Temporary leakage control Table 3.12 shows the temporary measures for leakage control taken from 1945 to 1946. A special unit was organized and exclusively charged with implementing these measures that were effective when the leak rate was high. Immediately after the Hanshin Earthquake in January 1995, temporary leakage control measures were taken in the early stages of the restoration work. However, as the leak rate decreased to a certain level, the measures became insufficient and other measures were employed.

Table 3.12 Temporary measures for leakage control

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1 Closing curb stops of unused service lines 2 Closing sluice valves of unused distribution mains 3 Plugging broken lead pipes by crushing 4 Installation of temporary curb stops

2 Systematic leakage control In 1947, the next measure taken was systematic leakage control. This measure comprised block leakage measurement, leak detection and leak repair. Figure 3.14 shows the procedure of systematic leakage control. At first, the objective area is divided into blocks using a utility map and the leakage volume in a block is measured. If the leakage volume is smaller than the allowable volume, the control work moves to the next block. If the leakage volume is larger than the allowable volume, leak detection and repair are carried out until the leakage volume is reduced to below the allowable volume. Initially, this measure was implemented only in high leak rate areas. But later, extremely high leak rate areas disappeared as systematic leakage control progressed and the objective area was expanded to the entire city. At the same time, this measure began to be implemented cyclically with a certain work cycle. The allowable leakage volume was set by block leakage measurements because significant expenditure and labour is required to detect and repair all existing leaks, including very small leaks. As the leak rate decreased, the allowable leakage volume was changed over time, as shown in Table 3.13.

Table 3.13 Allowable leakage for block leakage measurement (at water pressure of 2kgf/cm2)

Paved Road Unpaved Road 1947-1949 80m3/day/km 50m3/day/km 1950-1951 40m3/day/km 20m3/day/km 1952-1964 20m3/day/km 5m3/day/km

1965- 1m3/day/km (24m3/day/km) To improve work efficiency, newly developed instruments have been introduced into systematic leakage control work. Leak detectors and iron pipe locators came into use in 1949. Self-recording flowmeters were introduced in 1967. Until that time, for block leakage measurements, all curb stops in the work block were closed and the block leakage volume was measured directly. But from 1967, to eliminate the significant amount of time and labour needed to close and open all the curb stops, the minimum night flow measurement method was adopted and self-recording flowmeters were introduced. In 1986, leak noise correlators were introduced for leak detection work. 3 Distribution main and service line improvements In addition to the above leakage control measures, other preventative measures, namely distribution main and service line improvement projects, were commenced. Distribution main improvement was implemented in 1965 aiming to reduce leakage, excessive friction loss and turbid water occurrence in unlined pipes. Pipe replacement, inner surface re-lining, hose lining and inner pipe insertion methods were employed as improvements.

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Service line improvements have been implemented since 1960 with the aim of reducing leakage and maintaining sufficient flow capacity. Service installations are installed at customers expense and customers are responsible for maintaining service installations. However, in many cases leaks on service lines leading to meters are left as they are. Accordingly, Osaka Municipal Waterworks Bureau is improving service lines leading to meters at the bureau's expense in order to provide comprehensive maintenance of water supply facilities. To increase the effects of facility improvements, when a distribution main is improved, service lines connecting to that distribution main are replaced at the same time. Figure 3.15 shows the change in distribution main length by joint type. Unlined grey cast-iron pipes with lead joints were used until 1955 in Osaka City. To improve distribution mains, these unlined lead-joint pipes are being actively replaced or permanently repaired because they corrode easily and leak more than mechanical joint pipes with internal lining. As a result, the proportion of lead-joint pipes declined from 63% in 1965 to 13% in 1994. Figure 3.16 shows the change in service line length by piping materials. The lengths shown in Figure 3.16 are only the under road section. Lead pipes were the main piping material up to 1956, but the length of lead piping decreased by 39% by 1994. Conversely, the length of PVC pipes increased to 56% by 1994 with the progress of service line improvements. In addition to replacement of aged pipes, the following measures were also taken as service line improvements to facilitate the maintenance of service lines: Changing service line locations from private land to public roads; Simplification of complicated multi-parallel service lines; Changing meter locations from the inside of houses to the outside; C Discontinuance of systematic leakage control As a result of the systematic leakage control measures and facility improvements, the leak rate dropped steadily. However, when the leak rate fell below about 10%, the low leak rate reduced the efficiency of systematic leakage control. The cost of leakage control has also exceeded the cost of leak losses prevented by leakage control since 1988. To make matters worse, decreases in the leak rate and increases in the cost of leakage control resulted in a longer work cycle for systematic leakage control. If the work cycle gets longer, some underground leaks appear on the ground surface and are repaired immediately before the next leakage control work is implemented. This situation reduces the necessity and lowers the efficiency of systematic leakage control measures. For these reasons, systematic leakage control measures were discontinued in 1991. D Future prospects for leakage control The future prospects for leakage control by Osaka Municipal Waterworks Bureau are as follows. 1 Distribution main and service line improvements The first measure is to promote distribution main improvements and service line improvements as preventative measures for leakage control. Unlined lead-joint pipes and lead pipes still remain in the city, thus pipe improvements will continue to be implemented in the future.

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2 Inspection of third-party construction sites The second measure is to inspect construction sites of other utilities such as gas, sewer, electricity, telephone or building constructions, near water pipelines. On such construction sites, the probability that pipes will be damaged is relatively high, but it is also easier to inspect or repair pipe leaks because pavements and surrounding earth have been removed and sometimes pipes are exposed. 3 Formation of a block distribution system The third measure is to form a block distribution system in the pipe network. Block distribution systems can facilitate pressure control as well as detect and repair leaks. Distribution main improvements should be implemented in consideration of this measure.

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Figure 3.13 Change in leak rate

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Figure 3.14 Work Procedure for systematic leak control

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Figure 3.15 Distribution main length by joint type

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Figure 3.16 Service line length by piping material

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