ThermoFire heats up all the water in a nearby external tank, such as a solar water tank, conventional water heater, or water storage tank. The water is heated in the ThermoFire, then flows into the storage tank and back to the ThermoFire. The water continues to flow around the loop until all the water is heated. You build a fire once a day to heat up the volume of water.

The hot water is moved through the ThermoFire by using a small in-line circulating pump. Unlike thermosiphon, ThermoFire can be located away from the tank. The circulating pump produces the flow between the ThermoFire and the storage tank.