The check valve opening and closing parts rely on the flow and force of the medium to open or close automatically to prevent the medium from flowing back. The check valve belongs to the automatic valve category, which is mainly used in the pipeline where the medium flows in one direction, and only allows the medium to flow in one direction to prevent accidents. The check valve is also called a one-way valve or a non-return valve, and its function is to prevent the medium in the pipeline from flowing back. The bottom valve of the water pump suction valve also belongs to the check valve category.
Check valves can be divided into three types according to their structure: lift check valves, swing check valves and butterfly check valves. Lift check valves can be divided into vertical and horizontal types. Swing check valves are divided into single-flap, double-flap and multi-flap types. Butterfly check valves are straight-through type. The above check valves can be divided into three types in terms of connection: threaded connection, flange connection and welding.

The following points should be noted when installing the check valve:
1. Do not allow the check valve to bear weight in the pipeline. Large check valves should be supported independently so that they are not affected by the pressure generated by the pipeline system.
2. During installation, pay attention to the direction of the medium flow should be consistent with the direction of the arrow on the valve body.
3. Lift-type vertical flap check valves should be installed on vertical pipes.
4. Lift-type horizontal flap check valves should be installed on horizontal pipes