A swing type check valve is a check valve in which the disc, the movable part to block the flow, swings on a hinge or trunnion, either onto the seat to block reverse flow or off the seat to allow forward flow. The seat opening cross-section may be perpendicular to the centerline between the two ports or at an angle. Although swing type check valves can come in various sizes, large check valves are often swing check valves. Another variation of this mechanism is the clapper valve, used in applications such as firefighting and fire life safety systems. A hinged gate only remains open in the inflowing direction. The clapper valve often also has a spring that keeps the gate shut when there is no forward pressure.
These conventional swing type check valves are used in horizontal or vertical systems with rising flow to prevent flow reversal. These are suitable for multi-pump sewage water applications which have low to medium lift.