A peritoneal dialysis system includes a disposable cassette including a flexible sheet; a hardware unit including (i) at least one pump actuator and piston head moved by the pump actuator, (ii) at least one valve actuator, (iii) at least one sensor, and (iv) a disposable cassette interface for interfacing with the disposable cassette, the disposable cassette interface including: (a) at least one pump aperture, the at least one piston head moveable out of and retractable into the at least one pump aperture to move a corresponding pumping portion of the flexible sheet of the disposable cassette, the piston head moving within a vacuum chamber, the vacuum chamber enabling a vacuum to be pulled around the piston head to the flexible sheet of the disposable cassette; (b) at least one valve aperture, at least a portion of the at least one valve actuator located in the valve aperture to move a valve portion of the flexible sheet of the disposable cassette; and (c) at least one sensor aperture, the at least one sensor located in the at least one sensor aperture, the at least one sensor operable with a sensor portion of the flexible sheet of the disposable cassette.