Depends on your definition of cold and how your RV is set up...
I consider 40° cold
I have camped in sub zero temperatures, we slept with out canteens to keep them from freezing.
In really cold weather (low's20's) or God forbid colder, your best bet is to drain the water system completely and use water coolers or gallon jugs.
Hopefully someone with a similar unit to yours will be able to give you some more specific advice.
Aaron