The curling up of the water supply hose in the night time that boatto5er mentioned is not a bad idea. We towed back to southern Iowa in late Sept/early Oct this year and initially had some great weather. One day hit 80-degrees. We were in heaven. Several days later, the temps dropped with the cold air coming across the lake, and not absolutely certain what the night time low was, but I got up at about 7AM to 27 degrees F. Went to the galley to run water for coffee,,,,,,, and there was none....... Went outside to figure out what was happening, and low and behold,,,,, the supply hose between the hydrant and the RV was full and frozen. I quickly spun off the hose connection and found the hydrant itself as also froze. Went to the UDC and flipped the water supply to the 5er water tank, went inside and turned on the water pump for coffee. Everything was fine with the pump and RV supply tank. If I would have had my witts about me, I would have measured the water temp coming out of the RV tank up through the faucet, but I didn't.
I checked the basement temp (we have a temp sensor in the basement) and it said 48 degrees. Bare in mind that the sensor is mounted on the front of the basement wall. During that night, I had the fireplace on low, a small electric running on low and the furnace set at 69 degrees for makeup.
Next move was to put the supply hose inside the RV basement for a couple hours to let it thaw; and by that time, the outdoor park hydrant had also thawed. The bottom line here (if there is one), is that the first thing that froze was the supply hose to the RV. And since I had pressure in the hydrant, the head also froze. Had it been shut off and the hose disconnected, there shouldn't have been a problem there either in so much as the shutoff is beneath the ground.
I suspect that boatto5er is right about the night time issue; disconnect your hose, put it in your basement, and run off the RV's water tank and pump during the coldest part of your day (night time). Good luck,,,,, gebills.
