The low pressure gravity feed complete system consists of a vacuum glass tube collector, an insulated storage tank and optional stand parts (make up tank). The evacuated glass tubes are filled with water and exposed to sun, thus heating up the water in the glass tubes.

As the specific gravity of cold water is heavier than hot water, the hot water in the glass tubes starts rising in the insulated water tank, and the cold water in the insulated water tank sinks into the glass tubes. As this cycle is repeated, water in the solar water heater gets heated. This process is known as Thermosyphon and is based on natural convection.