Valves | Types | Distance between valves

Valves

A valve is a device which is used to regulate water supply in a water distribution system.

They are used for testing, inspection, cleaning and repairing of pipes. They are located at the road corners. Their number and the distance between them depends upon the area.

WASA and LDA recommendations

PHED recommendations

Types of valves

• Gate valves

The valve which is used to regulate the water supply or flow in the mains is known as gate valves.

When repairing is required, then supply has to be cut off. So gate valve is closed to discontinue the supply and repairing is carried out. These are also called as sluice valves.

• Globe valves

These are used in household plumbing. Due to their character of high loss they are not used in water distribution system.

• Check valves

These are uni directional valves. They are used to prevent reversal of flow. Check valve is installed at the end of the suction line and called as foot valve. They prevent draining of suction when the pump stops. These are also installed on the pump discharges to reduce hammer forces on the pump.

• Plug/Cone valve

These are used for water under high pressure, fir sewerage, oils, abrasive liquids and gases.

• Butterfly valves

These valves are used in low pressure applications, in filter plants and in water distribution systems where pressure may reach upto 800 kpa.

They are more suitable than gate valves in main pipe lines. They have lower cost, more compactness, minimum friction and ease of operation than gate valves.

However, these are not suitable for sewers.

• Pressure regulating valves

This valve regulate the pressure to required magnitude on downstream side.

These are used in lines entering in the low area of the city. If these valves are not provided there, then pressure will be too high.

• Air vacuum and air relief valves

These valves are provided at high points of the primary feeders or mains of water distribution. These are used to avoid air locking when the pipe is getting up and down appreciably.

In water there is always dissolved air, when temperature rises, air stability decreases and air bubbles come out. These bubbles are the cause for air locking. Air relief valves help in removing these bubbles.

• Blow off valves

These are provided at the lower points of the primary feeders or mains. At lower points of the primary mains, sediments carried by the water are deposited there. These sediments will reduce the water carrying capacity of the pipe. So these valves are provided and sediments deposited are removed through their opening.

• Altitude valves

These valves are used to close the water supply to an elevated tank, when the tank is full. This is done automatically.

Flow from the tank is permitted when low pressure below the valve indicates that water from the tank is required.