During the stage of no use, the temperature is the same between the inside and outside of the water, the water will expand when the temperature reaches 32°F（0°） even breaking the water pipe. This is a normal phenomenon and not a quality problem. Open the drain plug to drain off the residual water in the water heater and then screw it tightly if the environment where the water heater is installed drops below 32°F(0°C). This can prevent the cold from damaging the water heater.