PURPOSE: To eliminate inconvenience in handling and prevent the loss of natural resource by a method wherein a valve is opened by the operation of an operating unit while the valve is closed by detecting full-water and the elapse of time.

CONSTITUTION: When automatic hot-water supplying operation is effected by an operating unit 6, an automatic hot-water supplying signal is sent to a hot-water supplier 2 and a command generating circuit 10 and a command is sent from the command generating circuit 10 to a valve driving circuit 9 to begin with hot-water supplying. Simultaneously, a timer circuit begins time count. When the device is filled with water and a detector detects it, the command generating circuit 10 sends a full-water signal to stop the command, the valve 4 is closed by the valve driving circuit 9 and the hot-water supply from the hot-water supplier 2 is stopped. When the time count in the timer circuit 11 has exceeded a given time T, the command generating circuit stops to generate the command in spite of the signal of a water level detecting circuit, the valve 4 is closed and the hot-water supplying is stopped. The hot-water supplying may be effected fully automatically by only the operation of the operating unit.