Pipe Laying

Water Valves

Water distribution systems may involve various types of water pipes & water valves. Water Valves are used to control water distribution & maintain purposes. Three types of valves mainly can be identified in water supply project, which were

1.       Air valves

2.       Stop valves

3.      Wash-out

4.      Air relief valves

Air relief valves were installed to function of removal of air in the pipeline which was most important factor affecting the reliability and the stability of a water supply.

Air relief valves were installed either on the summit in a pipeline or in absence of a summit between two stop valves. The summit mentioned above can be highest point throughout the pipeline, but rather local highest points such as in sub section between two valves, Water Pipe Bridge or aqueduct. If there was not included any summit point, but pipe distance was long, sufficient number of valves are provided in adequate intervals.

Double orifice air relief valves were installed on pipes of DN400mm or larger in diameter. Stop valves were installed for the convenience in replacement of, and repairs to the air relief valves.

The protecting valve chambers was constructed for the buried underground. When an air relief valve box was installed where the groundwater was high, connecting pipe of sufficient height was also installed to protect the air relief valve from backflow of contaminated water.

Stop valve

It sometimes becomes necessary to stop the flow in a pipeline of service problems, repair work, draining for cleaning, branch connection work, maintenance requirements etc.

An effort was made to restrict the affected service area to minimize the problem. Therefore, an adequate number and type of isolating valves such as gate valves (sluice valves), butterfly valves, etc. were provided in a pipeline. Isolating valves were provided so that the fewest possible number need to function to limit the area affected by the water cutoff to as small as possible.

The two isolating valves were provided at that the branching points and three valves at the intersections were provided to be able to stop the flow at each pipeline. For the long pipeline, an isolating valve was provided at an appropriate point on the line to allow for partial suspension of service.

Stop valves were installed at bridges, before, and after rail road crossings; blow off pipes and on connecting to the distribution pipe line.

At points of high pressure, a bypass stop valve was installed on pipe line on 400mm DN pipes and above. When the pressure difference was very large one side of the other, valve operation for opening and closing might become difficult. So, the bypass valve was installed for 40m of water head and above 400mm DN in pipe size. This valve should be operated before the main valve. 

Wash out (Blow off) Facilities

To discharge soil, sand and grit remaining in the pipeline after laying and to clean the inside the pipe line or to remove stagnant water in the pipeline, a wash out facility was installed in a pipeline.

For a depression portion of the pipeline, a wash out facility was provided. Where there was a river or channel adequate for drainage along the pipeline, a wash out facility was installed near such a point if possible. In addition, the water sampling equipment was provided with the help of the wash out facility to allow water quality checks.

The drain pipe and main pipe were equipped with stop valves. There were two systems for stop valve installation: 1) providing two valves, one on each side of the wash out: and 2) providing two valves, one on each side of a stop valve on the main. The standard size of the drain pipe was 1/3to1/6 the size of the mains.

When the water surface level in the outlet facility was higher than the high water level of the drain channel to prevent back flow of discharged water, drainage chamber were provided between drain pipe and discharge outlet. The revetment nears the discharge outlet was thoroughly protected from the erosion and damage by discharged water.

Pipe Laying

Pressure Test

Fill pipe line with water

For the pressure test, The water filling process was carried out slowly verifying that air is being released from the pipe line. It was very important to make sure that air was actually being released during this process as the pipe line would become dangerous because of the compressed air caused by the insufficient air released.

If water leakage was discovered during this process, the pipe line must be repaired immediately.

The pipe lines were left in the water filled condition at least 24 hours to stabilize the pipe line.

Before applying the specified test pressure, air was that be expelled completely from the pipe, valve, and hydrants. If there was not permanent air vents at high points, the corporation cock was installed at such points so that the air can be expelled from it.

Installed equipment required for pressure test

The necessary equipment for the pressure testing work may be prepared as follows.

  • Pressure pump                                                1 set
  • Pressure gauge                                                1 set
  • Pressure recorder                                          1 set
  • Suction hose                             necessary length
  • Connection hose                     necessary length
  • Overflow hose                          necessary length
  • Water tank and water meter                      1 set
  • Connection pieces                                         1 set

Perform pressure test on pipe line


Each valve section of pipe was filled with water slowly and the specified test pressure based on the elevation of the lowest point of the line or section under test and corrected to the elevation of the test gauge. Valves were not

operated in either the opening or closing direction at differential pressures above the rated pressure. Any exposed pipe, fittings, valves and joints were examined carefully during the test. Any damage or defective pipe, joint, fitting, valves that were discovered was repaired.

Leakage tests

If a drop in pressure occurs, the quantity of water added to re-establish the test pressure were carefully measured. This should not exceed 0.1 liters per millimeter of pipe diameter per kilometer of pipeline per day for each 30m head pressure applied.

Drain pipe lines

After the completion of the test, water was drained from the pipe line. If the adjacent pipe section is to be tested, the water may be available for the next test.


Removal of protective work from the ends of test section

Protective work at the ends of the test section was removed when this pipeline is to be connected to an adjacent pipeline. However, when the adjacent pipeline was tested, these same protections may be available for it.

After the adjacent pipe line has been tested, the test section was connected to it.

Pipe Laying

Pressure Testing

Pressure Testing mean, A newly installed pipeline has to be tested to check the reliability of its performance before being brought into service.

The flow chart of the field hydrostatic test was shown below.

Decide of pressure testing section

The test section has to be determined after considering pipe line conditions and site situations, for example, the ups and downs of the pipe line, the position of valves and air valves, and the space for testing, the availability of testing water,

the number of joints, and other factors. While the test section was determined, the position of the valves and the valve chambers must be considered, because the valve and valve chamber can be useful as terminal points for the end of the test section.

Decide test pressure

The test pressure was determined by referring “installation of Ductile Iron Water Mains and Their Appurtenances”

Test pressure restrictions

  • Test pressure should not less than 1.25 times the working pressure at highest point of the test section.
  • Not exceed pipe or thrust restraint design pressure.
  • Be of at least 2 hours duration

Perform protective work at each end of the test section

  • Protective method using a valve chamber

If a valve chamber had enough capacity of install the equipment and apparatus required for pressure test, it can be used simple to carry out the pressure test inside since the valve chamber were designed to be able to resist the force of the water pressure when the valve was shut off.

Other protective methods

If a valve chamber cannot be used for the pressure test, protection for the end of the test section can be anchored by bolts (end cap)