PURPOSE: To eliminate perfectly the danger of receiving electric shock in he bathroom having high humidity by a method wherein hot-water in a bathtub is circulated through heat exchanging panel by hydraulic power provided in a hot-water path.

CONSTITUTION: A circulating device 4, supplying the hot-water in the bathtub into the heat exchanging panel 2, is consisting of vane wheels 9, 9', accommodated in mutually independent two chamber 8, 8' and connected coaxially. The vane wheel 9 is rotated by the hydraulic power when city-water enters through an entrance 10 and flows to an exit 11 through one of the chambers 8 while the other vane wheel 9' is also rotated simultaneously. According to this constitution, the hot-water in the bathtub 1 may be sucked from the entrance 12 of the other chamber 8' and discharged from the exit 13. According to the other method, city-water may be circulated by a method wherein it is flowed into the system through the entrance 20, a vibration valve 22 is pushed down to vibrate a diaphragm 26 into left-and-right and suck the hot-water from a suction port 28 through a non-return valve 27' while the hot-water is discharged through a discharging port 29.