A portable hemodialysis system is provided including a dialyzer, a closed loop blood flow path which transports blood from a patient to the dialyzer and back to the patient, and a closed loop dialysate flow path which transports dialysate through the dialyzer. In addition, the hemodialysis system includes two reservoirs which can be alternately placed in the dialysis flow path using various controllable fluid valves. The hemodialysis system may include a sorbent filter in the dialysate flow path which filters used dialysate. Alternatively, the filter may be positioned within a separate closed loop filter flow path which is isolated from the blood flow path and dialysate flow path. For this embodiment, the hemodialysis system includes additional controllable fluid valves which selectively connect the filter flow path to the reservoir which is not currently providing dialysis treatment to a patient.
