Abstract: The present invention presents an improved pump piston for pressurizing liquid dispensing containers, and more particularly improved air inlet valve designs for such pistons. According to the present invention, the inlet valves are located remotely from the lower end of the pump piston, such that they are protected from contamination by liquid product and resulting degradation of performance. One inlet valve design utilizes a lost motion connection between the pump piston and upper cap, with structural elements of the upper cap and piston cooperating to form an inlet valve that is opened to admit air into the interior of the piston when the cap is pulled upward and tightly sealed when the cap is pushed downward. Another inlet valve design utilizes slits in the wall of the piston itself and the flexibility of the piston material to form an inlet valve that is opened to admit air into the interior of the piston when the cap is pulled upward and tightly sealed when the cap is pushed downward.