Unless the coach is left unattended for a period of time in below zero temps, it is doubtful that the WH will freeze. Usually it is water in the lines that feed the hot and cold water systems that freezes. If the coach is being used, like our is sometimes in zero temps, I only needed a 100 watt light bulb in the wet compartment to prevent any freeze issues. The fresh water tank was kept full and used instead of hooking to park water.