Abstract: A pump for both filling and emptying containers with liquids, flowable solids, etc. has a body which is screwed into a bung hole in the top wall of the container. According to the state of evacuation or pressurization produced in the container by the pump, “liquid” will enter or leave the container via pipe passing through the body of the pump. The motive power for the pump is a compressed air source which provides air to a venturi positioned in a passage connecting the interior of the container with the exterior via vented chamber. Air flowing through air ports in the venturi generates a vortex which creates air flow through passage. By turning handle, the venturi may be rotated so as to reverse its orientation and thus reverse the direction of air flow to either pressurize or evacuate the container. Alternatively, a pair of oppositely-directed venturis selectively connectable to air passage may be used to perform the emptying and filling functions.