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.