A check valve assembly mounted on an end surface of a projection of a valve body. The check valve assembly includes a valve having a curved sealing surface disposed adjacent a fluid inlet intersecting the end surface of the projection. The check valve assembly further includes a rigid mounting plate having a cavity that receives and maintains the valve between the cavity and the fluid inlet. The curved surface of the valve partially extends into the fluid inlet and has a circular line of contact against the end surface of the projection around the fluid inlet to define a closed valve position. The valve is positioned away from the closed valve position to define an open valve position.