Check valve: check valve, also called as one-way valve or nonreturn valve. Its function is to prevent back-flow of the medium in the pipelines. The bottom valve of the suction pipe connected to the pump also belongs to the check valve. The opening and closing parts that work automatically through the power produced by the medium flow to prevent backflow are called check valves. Check valves belong to automatic valves, mainly used for one-way pipes which only allow medium to flow in one direction to prevent accidents. Lift check valves are vertical or horizontal. Its connection form includes screw joint, flanged joint and welding.