(1) Selection principle of valves for water supply pipelines

1. When the diameter of the pipeline is less than 50mm, a globe valve should be used; When the pipeline diameter is greater than 50mm, gate or butterfly valves should be used;

2. When it is necessary to adjust the flow and water pressure, regulating valves and globe valves should be used;

3. For parts with low water flow resistance (such as the suction pipe of a water pump), gate valves should be used;

4. Gate and butterfly valves should be used on pipe sections that require bidirectional water flow, and globe valves should not be used;

5. In places with small installation space, butterfly valves and ball valves should be used;

6. Globe valves should be used on frequently opened and closed pipe sections;

7. Multifunctional valves should be used on larger diameter pump outlet pipes.

（2） Selection of check valves

The selection of a check valve should usually be based on the following factors: installation position, water pressure before the check valve, airtightness requirements after closure, and the size of the water hammer caused by closure.

1. If the water pressure in front of the valve is small, a swing valve should be selected;

2. When strict requirements are placed on the airtightness performance after closure, a check valve with a closing spring should be selected;

3. When it is necessary to weaken the cut-off water hammer, a quick closing silencing check valve with damping device or a slow closing check valve should be selected;

4. The disc or core of a check valve should be able to automatically close under the action of gravity or spring force.

（3） Location of exhaust devices in water supply pipelines

1. For intermittent use of water supply networks, automatic exhaust valves should be equipped at the ends and highest points of the network;

2. The water supply pipeline network has obvious undulating sections that accumulate air, and automatic exhaust valves or manual valves are installed at the highest point of this section for exhaust;

3. Pneumatic water supply device. When using an automatic gas supply pneumatic water tank, the highest point of the water distribution network should be equipped with an automatic exhaust valve.