... steel with painting, or aluminum alloy, or stainless steel.4. Water tank heat insulation layer: 50-60 mm polyurethane foam.Working ... . Solar vacuum tube is plugged into the bottom of water tank. This water is filled inside the solar vacuum tube transmit solar ... both at home and abroad, including the US, Germany, Poland, India, Pakistan, Singapore, Vietnam, Korea, Turkey, Syria, the Middle East, Europe ...