When the burner fires, the thin layer of water heats to an abnormally excessive temperature that deteriorates the tank's glass lining, speeding up its rusting process. A small drain valve is on the surface of the water heater tank's jacket close to the underside. The end of the pressure and temperature relief valve extension pipe (usually operating down the aspect of the unit) on any kind of water heater have to be left open and exposed as properly. This pipe has to be free of obstructions in c...