To enable the back washing of a suction strainer of a pump mounted at a liq. spraying device without using a back washing pump.

One end of a liq. suction pipe 42 is connected to an inlet of a triple action reciprocating pump 16 and a strainer 24 is fitted at the other end. The strainer 24 is arranged in a tank 20 in which liq. 22 is stored. A discharge pipe 34 is connected to a discharge port of the triple action reciprocating pump 16, and the liq. 22 forcibly sent by the triple action reciprocating pump 16 is sent to a nozzle 30. In the discharge pipe 34, a line chamber 26 is disposed at a place apart from the triple action reciprocating pump 16 and an air chamber 36 is disposed at a base end side to accumulate pressure to the liq.. A branched pipeline 44 is branched from the discharge pipe 34 and connected to the intermediate part of the liq. suction pipe 42. At the branched pipeline 44, a solenoid stop valve 46 and a nonreturn valve 48 are disposed in turn from the discharge pipe 34 side.