Check Valves
A check valve is used to prevent backflow in piping systems. The valve opens due to the pressure of the fluid passing through the pipeline. Reverse flow closes the valve and prevents the fluid from moving in the opposite direction. Check valves do not require external control. They work automatically and hence do not have an operating handle or stem. The simplest check valves are designed with a one-way flap mechanism.
Check valves are generally small, simple, and inexpensive. Industrial applications of check valves include feed water control systems, gas systems that mix multiple gases into a single gas stream, and fuel and oxidizer mixing systems. In domestic applications check valves are often used to prevent mixing of a sanitary potable water supply with water from unsanitary systems.