Solar water heater frame 1.EN12975 solar keymark 2.Anti-freezen & pressurized 3.10 years warranty Solar water heater frame Material of Model:1.the heater pipe is made of red copper TU1+water,transfer power>150w,working pressure:4MPa,welding pressure:4MPa2.vacuum tube :tri-element,high boron and silicon content3.3,structure:gradual change SS-AL-Nx/Cu selective absorption coating;life:15 year3. ...