The thrust piston pump of a delivery apparatus for liquid media and the like is provided with a valve arrangement in the suction passage. The valve arrangement has two valve seats acting in opposing manner and is associated with a single common valve body. This permits a rapid transfer of the valve body into the closed position engaging on the valve seat, particularly during operation in an inverted position. In addition, the discharge passage has a mechanically openable discharge valve which can be simply opened by displacing the actuating head of the pump with respect to a collar of the pump piston.