The pump assembly comprises two unlocking check valves (4,5), which are assigned to two pumps (2,3). Two pressure connections (A,B) are provided for connecting a locking side of the unlocking check valves to the pumps. A suction connection (S) is provided for connecting an opening side of the unlocking check valves to the pumps. Actuating devices (12,13) are provided for an unlocking of the unlocking check valves by activating the pumps.