A double-acting pump for ejecting a product from a container, with a housing in which a piston with an axial bore is axially slideable and sealed by a first housing portion, with a hollow piston rod which extends the axial bore of the piston and is slideable in an opening of a closing cap of the housing and container. When an actuating head is actuated, it presses the piston against the force of a restoring spring toward a connecting pipe portion for an immersion pipe provided in the housing, so that a pressure is built up in a pressure chamber of the housing which presses a first valve closing piece in the connecting pipe piece against a first valve seat. In the non-actuated state, the piston releases as a result of the restoring force of a spring a passage between a pressure chamber and at least one opening in a second housing portion, wherein the connecting pipe piece has a second valve seat and a second valve closing piece which, in a position of the double-acting pump in which an actuating head is lower than the connecting pipe piece, the second valve closing piece assumes its closing position at the second valve seat, and the second valve closing piece assumes its open position in an inverted position in which the actuating head is higher than the connecting pipe piece.