A medical system is described. The system comprises: a liquid pump (20,120)； a tube (292) in communication with the liquid pump (20,120), the tube (292) having an end； a removable tip protector (280) configured to cooperate with the end of the tube (292), the removable tip protector (280) carrying a hydrophobic membrane (300) configured to allow air but not the liquid to escape from the end of the tube (292)； a sensor (68) configured to sense changes in pressure in the tube (292) and generate a pressure increase signal； and at least one processor (34) that operates with the liquid pump (20,120) to (i) pump liquid through the tube (292) cooperating with the removable tip protector (280), such that liquid does not escape from the end of the tube, (ii) receive the pressure increase signal indicating a pressure increase inside the tube (292), and (iii) cause the pumping to stop when air has been purged substantially from the tube (292). Also described is a method of priming medical tubing.
