It’s a Low pressure gravity feed system that consists of a vacuum glass tube collector, a storage tank, feeder tank and a flat roof stand. The evacuated glass tubes are filled with water and exposed to the sun, thus heating up the water in the evacuated glass tubes. As the 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 tank sinks into the glass tubes. As this cycle is repeated, water in the solar tank is heated. This process is known as Thermosiphon and is based on natural convection.