... Solar vacuum tube is pluged into the bottom of water tank, The water is filled inside the solar vacuum tube, Solar vacuum ... : galvanized steel with painting,or Aluminium alloy, or stainless steel.4. Water tank heat insulation layer: 50~60 mm polyurethane foam.5 ... bar.P.S.1. Controller can display the temperature, water level, automatically water loading etc.2. Electrical heater, which is backup fitting ...