PURPOSE: To enable a sufficient utilization of hot water to be attained from a solar hot water heater by a method wherein there are provided a pump for feeding hot water obtained from a solar hot water heater and a changing-over valve for selectively discharging hot water through a plurality of discharging ports in response to a temperature of the hot water.

CONSTITUTION: A pressurizing device 100 is constructed such that a hot water feeding pipe of a solar hot water heater is connected to a water feeding port 13 formed at a case 10, a pressure is applied by a pump 20 to hot water obtained from a solar hot water heater so as to feed the hot water to a changing-over valve 30. At this time, in the case that a temperature of hot water is high, the hot water is discharged out of a first discharging port 11. In turn, in the case that the temperature of the hot water is low, the hot water is discharged out of a second discharging port 12. In addition, in the case that the first discharging port 11 is connected to the hot water feeding pipe of the hot water feeder and the temperature of the hot water is high, energy consumption is not carried out at the hot water feeding pipe, but the hot water is supplied to a hot water and cold water mixing plug while the hot water is being pressurized. Further, the second discharging port 12 is connected to the water feeding pipe of the hot water feeder, the hot water is heated up to a predetermined temperature by the hot water feeder in the case that the temperature of the hot water is low and then the heated hot water is supplied to the hot water and cold water mixing plug or the like.