Radius Corner Water Heater Door Colonial White Water heater doors are exposed to the environment and get frequent use. So Suburban makes the door of galvanized steel finished in a tough, high solids baked enamel, making it especially chip and corrosion resistant. The standard door frame is installed without bending flanges or installing corner gussets, so installation is easier and the seal is better than competing units. The flush mount door is pulled tight against the sidewall without using screws that penetrate the exterior, giving it a neater appearance and reducing the possibility of leaks.