to work as a heat collector. As the sun shines on the collector, the water inside the collector tubes is heated. As it heats, this water expands slightly and becomes lighter than the cold water in the solar storage tank mounted above the collector. Gravity then pulls heavier, cold water down from the tank and into the collector inlet. The cold water pushes the heated water through the collector outlet and into the top of the tank, thus heating the water in the tank. The water tank preserves the heated water and decreases energy loss by layer of warmth preservation, while it stores water.