Vacuum Tube Solar water heater: CE certified, high efficiency, TIG welding, easy installation, reliable quality, ... certified, high efficiency, TIG welding, easy installation, reliable quality Solar Water Heater Vacuum Tube: Dia. 47/1500, Dia. 58/1500, Dia. 58 ... , 360mm, 500mm;Inner tank welding: Double sides argon protection welding. No corrosion;Outer tank shell: Stainless steel, Al-Zn zinc steel ...