solar water heater 1.ISO, CE, CCC approved 2.High quality and long life span at reasonable ... .Heat Preservation: imported polyurethane 55mm thickness5.Heat exchanging coil: copper 12mm diameter, 1.0mm thicknessHeat exchanger solar water heater Descripitionheat exchange solar water ... Galvanized SteelStructure of tank:4 holes for air vent,overflow,water inlet and outlet,electric heaterWelding:Argon arc ...