A pneumatic pump control system for sequentially switching on and off an electrically operated pump disposed in a waste water liquid storage tank The pneumatic pump control system comprises a pneumatic pressure accumulator that is disposed within the liquid storage tank at a predetermined level. The pneumatic pressure accumulator is a dome-type that defines an interior air chamber for containing air, and a lower opening disposed at an elevation that represents a zero reference level within the tank. The lower opening is in communication with the liquids in the liquid storage tank when the level of liquid is as high as the lower opening. A pressure transducer is operatively connected to the pneumatic pressure accumulator for communication with the interior air chamber to measure the differential air pressure between the air within the interior air chamber and the upper layer of air within the liquid storage tank. A first activation means responds to the output signal of the pressure transducer so that the pump is activated for a period of time to discharge a predetermined quantity of liquid. Following this, a clearing activation means responds by activating the pump for a period of time to discharge a predetermined quantity of liquid to lower the liquid level to a level below the zero reference level so that the air captured within the pneumatic pressure accumulator is recharged.