Snowman...too many variables to come to a system of protecting the water system in all conditions...lots of posts/threads on this forum to give advice and some "food for thought"...
In my opinion there are not any campers or trailers insulated sufficiently to protect the water systems under really severe cold for any length of time without internal heat source...think northern Canada; heck this winter I checked on temp at top of Whitefish ski lift and at 0900hrs it was -22F w/16mph wind.. what are temps and how long are they "low"...
Even my full 7 gallon water jug froze solid this winter on my ski trip [lowest I remember was -8 F]...as for anti-freeze....not my cup of tea, enough chemicals out and about that I don't want to put any in my drinking water system..but to each their own.
If you have a 110v hook-up and a small electric heater, all good. In boils down to sufficient propane or 110v...this of course doesn't work if you are driving for hours is sub-zero temps...
In the end you do your best and it still remains a crap shoot.
Phil
Edited by Wallowa, 08 April 2021 - 04:21 PM.