PURPOSE: To facilitate the change-over of hot and cold water by connecting a hot water channel and cold water channel to mixing valves, providing a three way valve to the hot water channel, and connecting the three way valve and a two way valve of the cold water channel before connecting them to the mixing valves of each channel.

CONSTITUTION: When hot water is run at a set temperature, the y-x direction of a three way valve 6 is only opened and, at the same time, a two way valve 7 is opened, hot and cold water separately run into a hot water channel 2 and cold water channel 4 respectively at flow corresponding to each set temperature, the hot and cold water are mixed with a mixing valve 5 and are discharged from a discharge port 9. After that, when the cold water is discharged, the valve 6 is opened in the z-x direction, and the valve 7 is opened. Then, the hot water is stopped by the valve 6, the cold water runs into the channel 4 through the valve 7 and, at the same time, it runs into the channel 2 through a linked passage 8, and it runs out to the discharge port 9 through a hot water side opening of the mixing valve 5. According to the constitution, the change-over of the hot and cold water can be easily and positively made without changing temperature setting.