PURPOSE: To provide a maximum range of water spray, pressure control circuit is provided between pressure pump and solenoid valve so that water is sprayed at the upper pressure limit of the electromagnetic valve.

CONSTITUTION: A valve 7 closes when water spray is finished and a pressure pump 2 stops, otherwise the valve 7 remains to be fully opened. At the start of the pump 2, a valve 6 is opened to allow water to pass the valves 6, 7 to return to the water tank 1, thus eliminating the need for no-discharge operation pressure of the pump 2. After that, a solenoid valve 10 is opened and the valve 6 is closed to allow water to pass through water feed pipe 9 and the electromagnetic valve 10 to be sprayed from a water discharge nozzle. At this time, the pump 2 is operated at its maximum efficiency of delivery pressure and quantity, allowing the delivery pressure is to be utilized as upper pressure limit of the solenoid valve 10. When water spray is finished, the valve 10 is colosed. The operation acts to relax pulsating pressure in the pipe 9 due to abrupt closing of the valve 10 and stop of the pump 2, and controls the pressure in the pipe 9 to less than the upper pressure limit of the valve 10.