Check valves, also called as one-way valves or non-return valves, are used to stop media from flowing backward. Bottom valves in water shut of water pump also belong to check valves. Headstock piece depends on media flowing and power to open or close automatically, in order to prevent backflow. Check valves are a type of automatic valves. Check valves are mainly used in pipes where media flow in only one direction. They allow valves to flow in only one direction in case of accidents.
 

 
1. Lift check valves: the disc slides with the vertical center line inside body. Lift check valves can be only installed at horizontal pipelines. When used for pipelines having high pressure and small caliber, ball can be used as disc. The shape of body of check valves is the same as that of globe valves (can be used with globe valves). For that, lift check valves have high coefficient of fluid resistance.
 
2. Swing check valves: The disc rotates with the pin roll outside seat. Swing check valves are in common use.
 
3. Butterfly check valves: Butterfly check valves have simple structures. They can be only installed horizontal pipelines. Butterfly check valves have poor sealing. 
 
4. Pipeline check valves: Pipeline check valves are a type of newly-developed valves. Pipeline check valves have small volume, light weight and good manufacturability while coefficient of fluid resistance is higher than that of swing check valves. 
 

1. When exhaust of pump having small caliber (DN<50mm), lift check valves are suitable.
2. When exhaust of pump having large caliber(DN≥50mm), swing check valves are suitable.