CHECK VALVES

A check valve, clack valve, non-return valve, reflux valve, retention valve or one-way valve is a valve that normally allows fluid to flow through it in only one direction. Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave.

https://industrialsurplusworld.com/blog/705-industrial-surplus-world-announces-a-valve-division-at-their-new-corporate-location