Wafer check valves, also known as dual-plate check valves, have two spring loaded half-moon shaped discs that rotate about their shaft. The disc plates are kept shut by a torsion spring. When fluid flows in a forward direction, the pressure of the fluid causes the disc plates to swing open, allowing flow. The check valve is closed by the spring as soon as flow ceases, before any reverse flow can occur.

A swing check valve consists of a flap or disc which hangs down in the flow path. With flow in the forwards direction, the pressure of the fluid forces the disc to swing upwards, allowing flow through the valve. Reverse flow will cause the disc to shut against the seat and stop the fluid going back down the pipe. In the absence of flow, the weight of the flap is responsible for the closure of the valve.

The valve is opened or closed by the valve disc to rotate around the spindle outside the valve seat; and it is an automatic valve when it is automatically opened or closed by the force generated by the medium flowing within the pipeline. Its major function is to prevent the backflow of the medium in the pipeline, reverse rotation of the pump and its driving motor, and discharge of the medium in the container. Full open according to API 6D requirements is available.