... vacuum tubes and spare parts for free Integrated Pressurized Solar Water HeaterSpecification:inner tank: food grade sus304-2B ... hail resistance: 25mmOptional: heat exchanger (red copper), electric heater (1.5kw, 2kw, 2.5kw, 3kw), assistant ... pressure, so do the water it produces.It uses the heat pipe to deliver the heat energy ... occasional tube breakage. Parameter Compact Pressurized Solar Water Heater