PURPOSE: To eliminate the generation of water hammering by moving gradually a flow rate control means and an ON/OFF means so as to open when a drive means drives in a forward direction and closing the ON/OFF means at a speed slower than a drive speed at which the ON/OFF means is opened when the drive means drives in the backward direction.
CONSTITUTION: When an attempt is made to depress a hot water supply switch to a bath tub 25 installed to a controller 43, a valve shaft 33 moves left slowly so that a bath valve disc 31 may be opened, thereby starting the supply of hot water to the bath tub 25. At that time, an attempt is made to control the flow rate with a flow rate control means 28 so as to adapt the supply temperature of hot water with a preset temperature of the controller 43. The flow rate control is carried out based on a change in the area of a gap between a cylinder section 45 on the side of a water quantity control valve 21 and an enlarged section 34 of a valve disc 36. When the supply of a fixed amount of hot water is completed, the valve shaft 33 moves right at a speed slower than the speed at which the bath valve disc 31 is opened so that the bath valve disc 31 may be closed, thereby suspending the supply of hot water to the bath tub 25 and hence eliminating the generation of water hammering.