Solar water heaters to solar energy into heat, from low-temperature water heated to high temperatures, to meet people in life, the production of hot water use. Solar water heater is a collector, storage tank and related annexes, to rely mainly on solar energy conversion into heat collector tube. Collector surface by the sun high temperature, tube surface temperature is low back positive, while the tube temperature reaction of water will produce, use cold water sinking floating principles to produce micro-circulation of water to achieve the required hot water.