The present invention relates to a pump arrangement comprising two pump units, each pump unit comprising a pumping cylinder, a reciprocally movable pumping piston, said pumping piston delimiting a pumping chamber in the pumping cylinder in communication with a pump port for fluids, an actuator connected to the pumping piston, and means for determining a value dependent on the position of the pumping piston in the pumping cylinder, said pump arrangement further comprises a first set of valves connecting the pump port of each pump unit to a source line and a delivery line for pumped fluids, wherein the pump arrangement comprises means for regulating the flow of the pumped fluids based on the value dependent on the positions of the pumping pistons in the pump units. The present invention further relates to a system comprising such a pump arrangement and a method for pumping fluids in said pump arrangement.