Abstract: A pump which will atomize a liquid without dribble is formed of a pump body having a pump chamber with a throat at the bottom thereof; a pump stem and piston assembly disposed in the chamber for reciprocal motion therein, an axial bore being formed through the bottom of said piston and stem terminating in an axial outlet port; a valve member having a top section sealing against said axial port and a bottom section passing through and sealing said throat after the initial operation when said pump is operated; and a spring biasing said valve member upward. The sealing area at the axial port is selected so as to be less than the sealing area at the throat at the bottom of the chamber whereby when a predetermined pressure is reached within the pump chamber the net force exerted on the valve member acts against the spring to open the axial port to the stem causing material to be dispensed at the predetermined pressure without dribbling.