Check valves are usually installed in the pipeline to prevent backflow. A check valve is basically a one-way valve in which the flow can flow freely in one direction, but if the flow turns, the valve will be closed to protect the piping, other valves, pumps, etc.

There are various types of check valves used in a wide variety of applications. Check valves are often part of common household items. Although they are available in a wide range of sizes and costs, check valves generally are very small, simple, and inexpensive. 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. The bodies (external shells) of most check valves are made of plastic or metal.