Abstract: A check valve controlled by the medium passing through comprising: a housing having an input opening on one side defining a valve seat and an output opening communicative with the input opening, a locking member disposed over the input opening of the valve seat and positioned on the seat, the locking member having a pivot axis at one end, a bearing cap mounted in and engaging the walls of the discharge opening, the cap having a pair of bearing side plates formed at one end, the side plates having laterial recesses formed therein for receiving the pivot axis of the locking member. There is also a spring coupled to the housing for urging the locking member against the valve seat.