PURPOSE: To perform the supply of hot water and water to a bathtub and the drainage of the bathtub to prevent the freezing of the water according to the heat receiving state by providing a water plug at a water supply tube to a solar heat collector and a hot water operation valve at a hot water exhaust tube to the collector.

CONSTITUTION: A water supply tube 7 and a heat collecting tube 6 are connected through a switching water plug 2 to a water tube 1, and a hot water operation valve 10 is provided at the hot water outlet of the tube 6, thereby supplying hot water from a tube 8 to a bathtub 3 by opening at higher than a set temperature of the hot water. The switchig water plug 2 has a cock 15 at the outlet side of the water plug 13 and an outlet 17 connected to the tube 7. Accordingly, an outlet 16 is confronted with the bathtub 3 to supply water to the tube 6, to supply water to the bathtub by turning a plug unit 18 and to drain hot water from the tube 6 to the bathtub 3 by closing the plug 13.