We frequently camp when it gets below freezing in the early spring and late fall. It is usually above freezing during the daytime, but sometimes only a few degrees. We have never had any problems, but we do run an electric heater and furnace at night. I like it cool to sleep, but not cold. We have a Duraflame quartz heater that we purchased at Sam's a few years ago that we carry with us for those times of cool weather. When it gets below about 40, we also run the furnace. We do have enclosed underbelly.
If it is projected to get below or about freezing, we unhook the fresh water hose because that is the first thing that will freeze due to the exposure to the cold air all around. We will open the sink doors before going to bed to make sure there is good warm airflow around the inside plumbing and the heat from inside will escape down through some of the holes in the floor to the underneath plumbing areas. With just a few hours of cold, it's not going to completely freeze the plumbing, maybe a little bit of ice, but nothing that will harm the pipes. Now, note that I said a few hours, not several days of below 32. We do not run water through our outside faucet until all threat of freezing temps are gone. It will still have the pink stuff in it in June when we first use it.
