Definition

The fixtures which are fixed along the distribution system to serve following purpose are known as valves.

Purpose

1. Control the rate of flow of water

2. Prevent or detect leakage

3. Meet the demand during emergency

4. Make the distribution system more efficient.

Type of valve

1. Air valve

2. Reflux valve

3. Relief valve

4. Scour valve

5. Sluice valve

1. Air valve

This are also called as air relief valve

Location

The air valve should be located at point which is closed to or above the hydraulic gradient.

Working

In the normal condition the camber is full of water drawn from water pipe.

The float therefore touches the roof of chamber and poppet valve is in a closed position.

When air from water pipe enters the chamber, it starts accumulating just below the roof of chamber.

This accumulating of air makes the lever to work and to bring down the float.

The pulling down of float by lever operation the poppet valve before escape of takes place through it.

The action of air valve is then repeated.

2. Reflux valve

Reflux valve is also known as check valve or non-return valve.

A Reflux valve is an automatic device which allows water to go in one direction only.

When flow of water is in direction of arrow as shown in fig below the valve swing and rotate around the pivot and it is kept and open position due to the pressure of water.

When flow of water in this direction ceases the water tries to flow in a backward direction But in this case the valve occupied its seat and it thus prevent passage of water in the reserve direction.

Location

The reflux valve is invariably placed in water pipe which obtains water directly from pump.

3. Relief valve

These are also known as the automatic cut off valve or safety valve or pressure valve.

When pressure of water exceed a predetermine limit the valve operate automatically

The load on spring is adjusted to the maximum pressure.

Location

The relief valves are located at every point along the water pipe where pressure is likely to be maximum.

4. Scour valve

This are also known as slice valve or shut off valve or stop valves, blow off valves or drain valve are wash out valves.

They are operated with hand and closed down are soon as clean water is seen passing through them.

Location

These valves are located at dead end and depressions are lowest point in main

5. Sluice valve

Sluice valve is also known as the gate valve or shut off valve or stop valve

These valves control the flow of water and are helpful in dividing the water main into suitable section

The rising or lowering of valve is carried out by rotating the handle from top.

Location

They are generally placed at a distance of about 150m to 200m and at all junctions.