1. Non-pressure solar water heater of all glass evacuated tube collector integrated with storage tank, are ideal for use in houses and other applications where cheap, reliable hot water supply is required. They are simple, economic and practical. 

2. As the specific gravities of hot water and cold water are different, cold water goes downward and hot water goes upward. 

3. When cold water in evacuated tubes is heated, it becaomes lighter and goes to the water tank, while cold water in the tank goes down to the evacuated tubes 

4. Through this circulation, the cold water in the water tank will be gradually heated