... steel,Such thick steel, to endure more pressure in the tank, 50-55mm polyurethane foam, guaranteemore hours for the water ... solar water heater Solar collector : adopt sectional metal heat-pipe vacuum tube, manifold box (SUS304-2B stainless steel for outer ... box),copper header pipe; support (1.2mm thickness stainless steel profiled bar) Pressure water tank : porcelain enamel Inner tank; with a copper ...