... WATER HEATER COST, SOLAR WATER HEATERS, SOLAR HOT WATER HEATERS, SOLAR HOT WATER, SOLAR WATER HEATER PRICE, SOLAR WATER HEATING, EVACUATED TUBES, VACUUM TUBES, HEAT PIPE SOLAR WATER HEATER, HEAT PIPE SOLAR ... heated. it becomes lighter and goes to the water tank .while cold water in the tank goes to the evacuated tubes4.Through this circulation ...