... solar water heater can work in high pressure 5. It uses the heat pipe which can deliver the heat rapidly 6. The vacuum tube ... connected directly with city water. 4. No water inside the evacuated tubes; The solar water heater can still in service even with several ... Magnesium bar, T/P valve, , sensor hole, water inlet and outlet hole, electric heater. Pre-heat Solar Water Heater with Assiatant Tank