Check valves are fluid control devices that restrict the flow of media in a piping system to one direction. This broadly defined check valve function plays different roles in various industries. Also known as non-return valves, one-way valves, or backflow preventers, check valves prevent flowing media from flowing back upstream.
A check valve comprises two ports - an inlet and an outlet - and a shutoff/closing mechanism. The unique characteristic of check valves that distinguishes them from other types of valves such as ball and butterfly valves is that, unlike these valves that require some form of actuation to operate, check valves are self-operating. Check valves function automatically, relying on differential pressure to effect control. In their default position, check valves are closed. When media flows in from the inlet port, its pressure opens the closing mechanism. When the inflow pressure drops below the outflow pressure due to flow being shut off, or the pressure on the outlet side becomes greater for any reason, the closing mechanism immediately closes the valve.
The closing mechanism in check valves is usually held in place by a loaded spring, a counterweight, or gravity. For the valve to open, the media has to overcome the force of the spring or closing mechanism.
VMS stocks both swing and in-line check valves with threaded, press, push and sweat connections in sizes ranging from 1/4” to 3” and in brass and stainless steel materials.  Our brands are the most trusted names in the industry; Boshart, Legend, Jomar, Nibco, Sharkbite, Viega and others.