Valves are necessary in water supply system, in order to regulate the flow of water and to minimize the wastage of water. Valves either start/stop the flow of water or control (throttling) the speed and capacity of water or direct the flow in one direction only.
Also read: What are different types of valves?
In a house, gate valve (stop cock/valve) is installed at the connection of mains with the branch line. It functions to start/stop water supply into a house. On opening of gate valve, water enters into house.
- In case of direct water supply system, gate valve is kept open so that water flow is available 24×7. It has to be turned off in case of repair maintenance of pipe work or plumbing accessories.
- In case of indirect water supply system, gate valve is turned on to fill water storage tank. Once the tank is filled gate valve is turned off.
Sluice Valve and/or Gate Valve functions strictly to either start or stop the flow. Gate valves are used for water supply system and sluice valves are used for slurries. Gate valve is opened by lifting gate/wedge from the flow of water, allowing all water to pass without resistance. Top end of stem (connecting rod/shaft) has hand wheel or motor to lift and drop the gate, and its bottom end has a gate of circular or wedge shaped to block the flow of water. It has a threaded stem; hence the valve has to turn multiple times in order to go from open to closed position and vice versa preventing water hammer effects.
Opening and closing of gate valve is perpendicular to line of flow i.e for a horizontal running pipeline stem is vertical and for vertical running pipeline stem is horizontal. Hence, they cannot be used to control flow of water or water pressure as it will cause wear and tear of gate.
Mainly two types of spindles (wheel to turn valve on and off, at top of the stem) are used for raising the gate of sluice valve.
- A raising spindle: In which a spindle is attached to the gate but gate dose not rotate with the hand wheel.
- A non-raising spindle: Spindle which is rotated in a screwed attachment in the gate.
The size of sluice valve is generally the same as the size of the main up to 300-mm diameter. For bigger diameters, the size of the valve is about two-thirds the size of mains subject to minimum 300 mm.
The valves are placed in valve chambers provided with caps or hand wheels for operation. The direction of opening of a valve may be clockwise or counter clockwise and marked on the outer end of the spindle.