PURPOSE: To remove the positional restriction of hot-water feed taps and to enable to install the hot-water feed taps even on the second floor, by providing a pressure detecting means in a hot-water feed pipe branched from a heat collecting pipe, and obtaining a pump starting signal from the output of said pressure detecting means.

CONSTITUTION: When a heat collector 1 is heated by the solar rays and the temperature difference of the heat collector 1 and a heat accumulating tank 2 is increased, it is detected by a high-temperature sensor 17 and a low-temperature sensor 18, and a pump 5 is set into operation by the aid of a control means 19. Here, since a two-way valve 8 is opened and a three-way valve 6 is communicated with a lower portion of the heat accumulating tank 2, water in the tank 2 is supplied to the heat collector 1, where heat is collected. On the other hand, when hot-water feed taps 13 is opened for feeding hot water, pressure in a pipe 4 is lowered and the two-way valve 8 is closed through operation of a pressure switch 10. At the same time, the three-way valve 6 is shifted to communicate with a by-pass pipe 7, so that hot water at the upper portion of the tank 2 is supplied to the taps 13 by the pump 5. Here, fluctuation of pressure caused, for instance, at the time of starting the pump 5 is absorbed by a tank 12.