solar hot water Working principleSolar vacuum tube was evacuated into the tank,the coating inside of tube can absorb more than 92% heat energy from sunshine,The cold water in water tank flows into the tube and become hot,because of differentdensity between cold and hot,there will be a natual circulation in the tube.Hot water will float back to tank.The polyurethane heat insulation layer can keep the water warm about 2days without any sunshine. Consumer can enjoy comfortable bathe anytime.Spesification