This Check valve is a mechanical device that permit liquids and gases to flow in only one direction, preventing flow from reversing. It is classified as one-way directional valves meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave. The check valve consists of four main components: the body, a disc, a spring and a spring retainer, and The weight of the brass valve helps to keep your suction line below the surface preventing air from being drawn into your pump. It prevents the suction hose backflow, which ultimately helps the pump to be restarted and primed when needed.