Non-pressure Solar Water Heater Features; 1) Inner water tank shell is made of SUS304-2B food grade stainless steel plates, 2） Outer tank shell is made of coated color steel plates or Zinc-Aluminium coated. Water is pure and drinkable 3) Heat insulation of water tanks adopts polyurethane foam and the thickness is 55mm 4) Silicon rings to connect and seal them 5) Capacity: 100L, 150L, 200L, 250L,300L 6) The life of the water heater can be 20 years. 7) Whole strong borosilicate vacuum tubes adopt super hard borax and silica glass 8) Absorption rate: =93%, thermal radiation rate: =6% 9) It resists 25mm hail 10) Temperature when exposed to sun without water: 250°C, 2 hours to boiling point if using single tube 11) If you use electrical appliances, it will begin to work when the temperature of the water is below 60°C, and will switch off automatically when the temperature reached 60°C. 12) You have to test the water temperature before using, in order to avoid scalding