PURPOSE: To provide a pump appropriate to pump up sludge or solids, by connecting an air feed pipe to a blower, opening the pipe into the pump and regulating the pumped-up quantity by the quantity of air forcedly conducted from the blower into a sucked liquid.

CONSTITUTION: One end of the air feed pipe 3 whose other end is coupled to the blower 2 installed above the level of liquid is opened into the suction port 5 of the pump 4 or the like. An air regulating valve 6 is provided in the upper part of the air feed pipe 3. When the pump 4 is driven, air is forcedly supplied through the air feed pipe 3 and mixed into the liquid sucked through the suction port 5. As a result, the pumping action is reduced, namely, the pumped-up quantity decreases. Then, the quantity of the air from the blower 2 is appropriately controlled to enable the regulation of the pumped-up quantity in a wide range without changing the inside diameter of a duct. Therefore, the clogging of the sludge or solids in the duct and the wear of a valve can be prevented.