Patent ID: 8556225

Claim:
A pumping system for pumping a liquid, comprising: a pump inlet disposed above a pump outlet; a pump inlet valve and a pump outlet valve under control of at least one controller; a pump comprising a movable membrane positioned opposite a rigid inner wall, the membrane and rigid inner wall together forming a liquid pumping chamber communicating with the inlet and the outlet and configured to contain and move the liquid out of or into the pump through the outlet or the inlet of the pump as the membrane moves toward and away from the inner wall; wherein the controller is configured to determine the presence of gas within the liquid pumping chamber, wherein at least a portion of the membrane is prevented from contacting the inner wall so that a residual volume able to contain a residual gas and/or a residual liquid remains within the liquid pumping chamber, and wherein the controller is configured to control operation of the pump inlet valve and the pump outlet valve in order to direct the contents of the liquid pumping chamber to the pump inlet if a pre-determined amount of gas is detected in the liquid pumping chamber.