Valves for drainage pipes

Valve selection and setting parts

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Valves used for water supply pipes are generally selected according to the following principles.

When the diameter of the pipe is smaller than 50mm, the globe valve should be used. When the pipe's diameter is larger than 50mm, the gate valve and butterfly valve should be adopted.
When the flow and water pressure need to be adjusted, the regulating valve and globe valve should be selected.
It is recommended using a gate valve for parts with low water flow resistance, for example, water pump suction pipes.
Gate valves and butterfly valves shall be used for the pipe sections where the water needs to flow in both directions, and the globe valve shall not be used.
Butterfly valves and ball valves should be used for pipes with small installation space.
A globe valve should be used on the pipe section that is frequently opened and closed.
Multi-function valves should be used on the water outlet pipe with larger diameters.

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The following parts of the water supply pipeline shall be provided with valves.

The water supply pipe of the residential area from the inlet of the municipal water supply pipe.
The water outlet pipe of the water pump and the water suction pump of the self-priming water pump.
Inlet, outlet and drain pipes of the water tank.
Inlet water supply pipes for equipment such as heaters, cooling towers, etc.
Water distribution pipes for sanitary appliances such as large and small urinals, washbasins, showers, etc.
Some accessories such as automatic exhaust valves, pressure relief valves, water hammer eliminators, pressure gauges, sprinklers, etc., in front of and behind the pressure reducing valve and backflow preventer.
The drain valve should be installed at the lowest point of the water supply pipe.

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Check valves generally should be selected according to factors such as the installation location, the sealing performance requirements after the valve is closed and the water hammer when the valve is closed.

When the water pressure before the valve is small, the swing type, ball type and shuttle type check valve should be used.
If the sealing performance should be very good after the valve is closed, a check valve with a closing spring should be used.
When the water hammer needs to be reduced or eliminated, a muffler check valve or low speed closed check valve should be selected.
The valve clack or valve spool of the check valve should be able to be closed under the action of gravity or spring force.

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A check valve shall be installed on the following sections of the water supply pipe

Inlet pipes of closed water heaters or water equipment, outlet pipes of water pumps, outlet pipe sections of water tanks, water towers and highland water pools whose inlet and outlet pipes share one pipe.
Please noted that the pipe section which is installed with the pipe backflow preventer does not need to be installed with a check valve.

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The following parts of the water supply pipeline shall be installed with exhaust devices

For the intermittently used water supply pipelines, an automatic exhaust valve shall be installed at the end and the highest point of the pipelines.
The air pressure water supply device should be equipped with an automatic exhaust valve at the highest point of the water distribution pipeline when the automatic air supply pressure water tank is used.

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