A check valve is a mechanical device used as an industrial/plumbing fitting, which normally allows fluid or gas to flow through it in uni-direction. A double check valve is often used to prevent back flow and to keep potentially contaminated water from siphoning back. Clapper valves, a type of check valve is used in or with firefighting, and has a hinged gate (often with a spring urging it shut) that only remains open in the outflowing direction.

Types of Check Valves

• Single Disc Swing Valves : These valves can be mounted both vertically as ell as horizontally and are designed with a closure element attached to the top of the cap. This closure element can be pushed aside by the flow, but swings back into the close position upon flow reversal.
• Double Disc or Wafer Check Valves : These valves consist of two half-circle disks hinged together that fold together upon positive flow and retract to a full-circle to close against reverse flow.
• Lift-Check Valves : These valves can operate in either vertical or horizontal mounting.
• Silent valves : These valves are quite similar to lift check valves with a center guide extending from inlet to outlet ports.
• Ball-Check Valves : These valves are good for most services and can even handle fluids that produce gummy deposits. Since the disc is free to rotate, this all helps to keep the valve seats clean.
• Cone Check Valves : These valves use a free-floating or spring loaded cone resting in the seat ring as the closure element. Incase of a reverse flow, the cone is forced back into its seat preventing back flow.