To prevent malfunction by securing a stable inoperative flowing water amount even at a high pressure for a wide using pressure range acting on the primary side.

The flowing water detector 10 is provided in the middle of piping for supplying pressurized water from a pressurized water feeder to a head, a valve body 18 is turned to a closing position by gravity in the same pressure state of the primary side and the secondary side, the valve body 18 is opened with the primary side pressure by the pressure decline of the secondary side piping to continuously supply the pressurized water from the pressurized water feeder, and a flowing water detection signal is outputted after the prescribed delay time from the opening of the valve body 18 by a pressure switch 28. Bypass piping 32 which bypasses the primary side and secondary side of the flowing water detector 10 is provided with a constant flow valve 34 for supplying, to the secondary side piping, the inoperative flowing water amount to be a prescribed fixed flow rate to the supply of the pressurized water for elevating the pressure of the secondary side piping to a prescribed pressure.