Dave: water freezing at 0 degrees never measured it.Well my tank did not freeze and my hoses were not frozen but the heater froze due to been lower The heater due to been steel its a better conductor of cold and next to the skin of the van. Drain is the only way or heat the van, I have never had anything freeze in my area. But last thursday was ffffffshhhhhhh rrrrrr cold. Its bust at 12 o clock is the morning while I had a lunch break.