... can be used in the rain area Manufacturer non-pressurized solar water heater 1,vacuum tube length:47/1500mm,58/18002,vacuum tubes ... .31mm5,Insulation:foaming polyurethane thickness:50mm or 55mm6,Optional electric heater:220v-240v 1500w/3000w7,frame material :202 stainless steel8,we ... freely .it is suitable for the many residentbuildings. non-pressurized solar water heater