hj
If, and this is a big IF, the piping is run properly, i.e., the supply to the last fixture slopes constantly upward, and the return to the water heater flows constantly downward, then a gravity system will work as good as a pump system and use less energy since less water is being returned to the tank to be reheated. However, it is often difficult to install the piping correctly, in which case a gravity system will not work at all and a pump has to be installed.
