... -1800mm co-axial structure high borosilicate 3.3 glass vacuum tube with tube wall thickness of 1.6mm.Inner tank materialSUS304 ... resistanceDia=25mmGuarantyWater tank for 5 years, tube and frame for 15 years1,vacuum tube length:47/1500mm,58/1800.2,vacuum tubes:15pcs, ... ,the tap water flow in the tank ,if the water is full,it will close the valve automatically evacuated glass tube for solar water heater