If you're worried about your water freezing, IMHO I don't think your water will if the only gets to just below 32 degrees for only a few hours. I've had water in my camper many times when the temp drops just below freezing all night without a problem. I don't doubt it would freeze if the temps stayed below freezing for a day or more...then I'd worry.
2000 Cherokee 29BH with 6V batteries, LED lights & 400 watts of solar power, flipped axles and raised. 2007 Tundra 5.7L DC-LB with lots of mods. C-co, 8/158th AVN Maint.