Abstract: Provided is a water supply/drainage pump including: an air-cooled internal combustion engine section; a pump section configured to supply/drain water by being driven by the engine section; and a heat exchanger block arranged between the engine section and the pump section and configured to cool exhaust gas from the engine section. The heat exchanger block is mounted to a body of the pump section through intermediation of a first sealing plate. A fuel tank is mounted above a body of the engine section. Except a part corresponding to the pump section, parts corresponding to the engine section, the heat exchanger block, and the fuel tank are covered with a casing. The heat exchanger block is provided with a cooling passage, an exhaust passage, and a muffler passage.

Abstract: Provided is a water supply/drainage pump including: an air-cooled internal combustion engine section; a pump section configured to supply/drain water by being driven by the engine section; and a heat exchanger block arranged between the engine section and the pump section and configured to cool exhaust gas from the engine section. The heat exchanger block is mounted to a body of the pump section through intermediation of a first sealing plate. A fuel tank is mounted above a body of the engine section. Except a part corresponding to the pump section, parts corresponding to the engine section, the heat exchanger block, and the fuel tank are covered with a casing. The heat exchanger block is provided with a cooling passage, an exhaust passage, and a muffler passage.

Abstract: Provided is a pump apparatus capable of improving the performance in a wide operation range from an operation area with a low pressure and a high flow rate to an operation area with a high pressure and a low flow rate while suppressing a rated output of a motor used to drive a pump. A rotation speed of a motor 20 is controlled so that the rotation speed of the motor decreases with an increase in the load of the motor 20 driving a pump unit 10, the rotation speed thereof increases with a decrease in the load thereof, and the load does not exceed a predetermined upper limit. For this reason, it is possible to improve the performance in a wide operation range from an operation area with a low pressure and a high flow rate to an operation area with a high pressure and a low flow rate compared to a method of the related art of uniformly keeping a rotation speed of a motor.