Master plumber Dave Yates likes the simplicity of a gravity-fed system when it’s applicable. A gravity-fed system relies on thermosiphoning, in which hot water rises to the top of the system and denser cold water falls to the bottom. For such a system to work, the water heater needs to be located below the hot-water taps it will serve. While pipe insulation and short plumbing runs help to reduce standby heat loss and energy consumption, this system uses more energy than others because it is operating 24 hours a day. However, because there are no pumps to install or maintain, this system is arguably the most user-friendly.
1. Hot water rises to the top of the system, closest to the fixtures.
2. Water that cools in the system is heavier and denser than the hot water being supplied and falls through a return line to the lowest point in the system, the water heater.
3. A check valve keeps water in the water heater from flowing back into the return line.
4. Cool water is heated and circulated through the hot-water supply lines, starting the thermosiphoning process over again.