... of Outer Tank: Color steel, thickness: 0.4mm Copper Coil: diameter : 12mm, thickness: 1mm Heat Preservation : ... water heater is our newest products, adopt the copper coil , it improves the problem of traditional solar ... water is limited, few out water , heat for long time, the water quality is worse and ... worse. The technology we first research heat for twice is successful, let the connection of ...