Pumping mechanisms for performing peritoneal dialysis and the like employ a pumping mechanism comprising a diaphragm that operate in response to applied fluid pressure. Flexible tubing is attached to the pumping mechanism for carrying liquid to and from the patient's peritoneal cavity. An actuating station for pumping mechanism receives the pumping mechanism and attached tubing. A pressure transfer element conveys fluid pressure to the diaphragm for moving liquid through the cassette. An occluder element contacts and crimps closed the tubing attached to the cassette. A first reservoir inflates with positive fluid pressure for contacting the pressure transfer element to hold it in operative contact against the diaphragm. A second reservoir inflates with positive fluid pressure for contacting the occluding element to hold it away from crimping contact with the tubing. At least one of the first and second reservoirs also transports fluid pressure to the pressure transfer element for conveyance to the diaphragm.