A check valve, or one-way valve, is designed to allow fluid to flow through it in only one direction. They are ideal where back-flow could potentially cause damage to pumps, filters, or process equipment.

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 exit.

There are various types of check valves used in a wide variety of applications such as water and chemical. Swing, ball, Y-check, spring and wafer are a few of the different types of check valves.

Although they are available in a wide range of sizes and costs, many check valves are small and simple. Check valves work automatically and most are not controlled by a person or any external control; accordingly, most do not have any valve handle or stem.