A peritoneal dialysis system includes a dialysis machine including a pump chamber and a pump actuator moveable within the pump chamber; a pumping cassette including a rigid portion defining a pump well and a flexible membrane covering the pump well; and wherein the dialysis machine is configured to be mated with the pumping cassette so as to hold a vacuum between the pump chamber and the flexible membrane, the vacuum operable to cause the flexible membrane to follow the pump actuator as the actuator is retracted from the pump well of the rigid portion, the pump actuator operable to cause the flexible membrane to move into the pump well as the actuator is moved into the pump well.