PURPOSE: To prevent water from being supplied with a drain valve open by a method wherein switching devices are provided to cut off the power supply to a driver every time the driver changes over the connecting state of a four- way valve, and an operation switch is furnished between the switching devices and a power source to perform change-over between water supply and drain.

CONSTITUTION: A power source 15 and a driver 10 are electrically connected by two lines of wires through a remote operation switch 16, and two drain side switches 14a and 14c and two water supply side switches 14b and 14d are respectively grouped and connected in parallel in the middle of the lines. Therefore, the driver 10 is brought in operation every time of on or off operation of the remote operating switch 16, and a rotary body of a four-way valve and rotors of the switches are turned for 90°, causing the rotors to press one of four switches 14a-14d to stop a motor of the driver 10. Thus, as a hot-water supply apparatus and a drain pipe are controlled by the sole four-way valve, water is prevented from being supplied with the drain pipe open.