The thermo-siphon system is a kind of non-pressurized solar water heater. It is SANGLE's most straightforward, low cost and energy efficient solar system. It requires low maintenance. Its high efficiency provides hot water after just a few hours of sunlight.

　　This simple and economic system is an Open-loop system . It relies on warm water rising, a phenomenon effect, to circulate water through the tubes and to the tank. Mains Water flows into to the tank and then to the lower part of the vacuum tubes where it is heated. The water ascends in the tubes as it is heated and flows on to the tank, and from there on to the user.