Abstract: A pump arrangement for pumping a liquid, in particular a liquid contaminated with dirt particles, the pump arrangement having at least one working chamber (1, 2, 11, 12) and at least one delivery piston (3, 4, 13), and at least one inlet valve (7) and at least one outlet valve (8), and the delivery piston (3, 4, 13) being movable in order to suck liquid into the working chamber (1, 2, 11, 12) through the inlet valve (7) and to eject liquid out of the working chamber (1, 2, 11, 12) through the outlet valve (8), and the pump arrangement having a wear-monitoring device (40) for monitoring the wear on the inlet valve (7) and/or outlet valve (8) with at least one pressure sensor (41) and one pressure evaluation unit (42) for processing pressure measurement values output from the pressure sensor (41), wherein the pump arrangement, for the purpose of moving the delivery piston (3, 4, 13), has a drive fluid system (20) that can be operated with a drive fluid, and the pressure sensor (41) of the wear-monitoring device