In a check valve or stop/check valve comprising a housing having an inlet port, an outlet port and a valve seat between the two ports, a valve disc moves axially within a valve housing between open and closed positions, so that fluid flow applies pressure against the valve disc to automatically open the valve, but when the fluid stops or reverses, the valve automatically closes to prevent backwash. Under conditions of pulsating, low-volume fluid flow, a ridge on the valve seat and a deflector ring on the valve disc deflects the flow of fluid, thereby using the velocity of fluid to increase pressure against the valve disc so as to smoothly and gently move the valve disc, reduce vibration of the valve disc and prevent it from striking the valve seat.