... 1% spare vacuum tubes and spare parts for free Integrated Pressurized Solar Water HeaterSpecification:inner tank: food grade sus304-2B stainless steel, ... preservation: 72-80 hours hail resistance: 25mmOptional: heat exchanger (red copper), electric heater (1.5kw, 2kw, 2.5kw, 3kw), assistant tank( 5L ... still work in the event of occasional tube breakage. Parameter Compact Pressurized Solar Water Heater