Too many things to read on the internet on this subject. I've talked to several people in our travels. Some succeed with no more than insulation on the hoses and leaving a tap running as mentioned above, and some have heat tape and other things in place. For us, for the times we have been in the teens, we just fill the water tank, disconnect and drain the water hose and reconnect in the morning when the sun comes out. A pain, yes it can be, but it beats a frozen line. If it's going to get so cold my enclosed tanks start freezing, even with the heat pads, I'm moving elsewhere to a warmer area, if possible. Of course with this year's winter, I think everybody got a dose of major cold, and there weren't many places to go that weren't below freezing at one point.
John and Rebecca Dickson
Emma-7 / Little John-5 / Iva-1
Full Timing Again, Rev B
2013 Ford F-350 Lariat CC LB PSD
2015 SOB TT - With OC's Awning Poles (#8)
At least in Heaven, RVs will be perfect, and I won't have to keep fixing them.