WATER SUPPLY DEVICE

PROBLEM TO BE SOLVED: To provide a water supply device which is excellent in pressure responsiveness without using a flow rate detection means, has little change of discharge pressure in the same water quantity even if suction pressure changes and is capable of performing a fixed control of predictive estimated terminal pressure. SOLUTION: This device is provided with a pressure sensor 16 detecting suction pressure of a pump 13, a motor 14 driving the pump 13, an inverter 19a making this motor 14 perform a variable speed operation and a control part 19 controlling the operating frequency of this inverter 19a. The control part 19 is provided with a calculation means changing a maximum frequency of the operating frequency according to suction pressure of the pump 13 detected by the pressure sensor 16 and controlling discharge pressure of the pump 13 so that estimated terminal pressure may be constant.