Disclosed herein are water purification and supply systems for medical devices and methods of using. In an embodiment, the system includes a dialysis system including a filtration system capable of filtering a water stream, a water purification system capable of purifying the water stream in a non-batch process, a mixing system capable of producing a stream of dialysate from mixing one or more dialysate components with the water stream in a non-batch process, and a dialyzer system. The dialyzer may be a microfluidic dialyzer capable of being fluidly coupled to the stream of dialysate and a blood stream. The water purification system includes an RO filter 6122, a proportioning valve 6165, a heater 6150, first and second heat exchangers, and a throttle valve 6160.