... water in 24hours solar water heaterComponent of Production: Material of Inner Tank: SUS304-2B Stainless Steel, thickness: 0.4mm, 0 ... .6mm Material of Outer Tank: Color steel, thickness: 0.4mm Copper Coil: diameter : 12mm, thickness: 1mm Heat Preservation : polyurethane foam ... pressurized solar water heater is our newest products, adopt the copper coil , it improves the problem of traditional solar water ...