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 determining a value dependent on the position of the pumping piston in the pumping cylinder, said pump arrangement further comprises a inlet and delivery 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 at least one regulating unit the flow of the pumped fluids based on the value dependent on the positions of the pumping pistons in the pump units. Also a system comprising such a pump arrangement and a method for pumping fluids in said pump arrangement.