hot water in this embodiment the inlet pipe 113 is a cold water supply pipe that is connected to a water pipe and provided to a shower and the outlet pipe 114 is a cold water pipe that is provided for a showerhead that has undergone heat exchange with waste hot water the inlet pipe 113 and the outlet pipe 114 can be made of a stainless material to prevent corrosion the height of the tub 110 is set larger than the diameter of a heat collecting pipe or heat transfer pipe 121 of the heat exchange unit 120 such that the heat exchange unit 120 including the heat collecting pipe 121 can be completely submerged in the waste hot water filled in the tub 110 it is preferable that the tub 110 is made of a material having corrosion resistance such as stainless steel because it contacts with water for the characteristic a cover support portion 119 that protrudes is formed at a predetermined distance from the upper end inside the side 112 of the tub 110 the cover support portion 119 supports the upper cover 130 covering the tub 110 in this embodiment the distance between the cover support portion 119 and the upper end of the tub.