check valve

A check valve is an automatic valve that allows fluid to flow in one direction and closes to resist reverse flow. It opens when the forward pressure difference is sufficient to move its disc, ball or poppet away from the seat. As forward flow falls, gravity, a spring or reverse pressure helps return the closure member to the seat, depending on the design. Check valves are also called non-return valves (NRVs) or one-way valves. Their main purpose is to help protect pumps, pipi