in this type of solar water-heater no pump has been utilized and the process of water circulation is performed using solar energy. The water is heated by absorbing energy through heat collector plates. Due to temperature fluctuations, the density of the beginning and the end of riser changes and leads to thermosiphon properties in the riser. Consequently, this process transfers hot liquid to the storage tank. If the system is direct, the heated liquid is the water to be consumed, and if the system is indirect (double-walled storage tank), the heated liquid (solution of water and anti-freeze) will be heated in the outer wall of the storage tank and subsequently will return to the collector. The principle of thermosiphon is adopted in Sunshine solar water-heaters. A double-walled water storage tank is placed on top of the solar collector, and a closed circuit is formed between the second wall and inner pipes of the solar collector. The sun shining on the surface of the solar collector, heats up the liquid inside and the natural flow of liquid between the collector and the tank heats up the water inside the main tank. the thermosiphon circulation lasts as long as the solar energy is available and it will stop as the sun sets.