The hemodialysis system includes a closed loop dialysate flow path which includes a dialyzer and a reservoir for storing dialysate, and a closed loop blood flow path which passes through the dialyzer in the opposite direction as the dialysate flow path. In addition, the hemodialysis system includes pumps for pumping dialysate and blood through their respective flow paths, a flow sensor for measuring the flow rate of dialysate in the dialysate flow path, and a level sensor for measuring the level of dialysate in the dialysate reservoir. A processor is connected to the flow sensor, reservoir level sensor and pumps to provide a first closed loop control system including the processor, flow sensor and a first dialysate pump, and a second closed loop control system including the processor, level sensor and a second dialysate pump which enable the processor to initiate, monitor and maintain ultrafiltration.
