I disconnect the water supply hose from the RV and drain the hose, run off on-board water for the night. All the water plumbing is within the insulated and heated interior so they are fine. One exception is the outdoor shower, it is in an outside compartment that is only protected by the plastic door. There may be enough heat from the interior to keep that faucet from freezing, but I usually will put a small towel or crumpled newspaper inside the door to help insulate from the outside temps - so far no problems.
Make sure the waste tank heaters are on. Keep the waste tank valves closed and run the macerator pump to drain as much water out of the pump as possible.
Also, we keep an electric heater running all night so that the noisy gas furnace does not need to be used at night.
This has worked for us in lower temps than you are expecting to see, good luck and have fun,
Bob
