Abstract: A vacuum-operated liquid pump includes a pumping member and a housing defining a pump chamber in which the pumping member moves along suction inlet and pressure discharge strokes. The pumping member divides the pumping chamber into a liquid space on one side of the pumping member and a gas space on the other side of the pumping member. A liquid-supply communicates with the liquid space for responding to movement of the pumping member along its suction inlet stroke to deliver liquid to the liquid space. A liquid discharge also communicates with the liquid space for responding to movement of the pumping member along its pressure discharge stroke to discharge liquid out of the liquid space. A passage communicates with the gas space for placing the latter in communication with a source of vacuum, while a valve cooperates with this passage for alternately placing the latter in communication with the source of vacuum and in communication with the outer atmosphere.