Hot water
Sizing hot water tanks, why smaller is often smarter
...water flows down the pipe, it pre-heats the incoming cold water headed for the water heater. This can raise the incoming water temperature from 50°F (10°C) to over 75°F (24°C), meaning the water heater has to do significantly less work. In many cases, a DWHR system can make a small 8-gallon tank perform like one twice ...
