Here are two ways I do it in the winter.> Method 1 is prefered by me for logistic reasons.
A tank of water lasts me up to 3 weeks. perhaps longer.
I fill the on-board 80 gallon fresh water tank, then disconnect and DRAIN THE HOSE Tanks on this class A have a couple different heat methods so are good down into the teens.... Park can take care if it's problems (in your case you would need to see method 2: WHen I change parks (2 weeks later) I top off again drain hose and do my week out.
If the outside lines freze. Who cares they are not my problem .. You however DO have a problem.. ONE TIME When I* went to leave here last summer I was unable to take on water.. Park was froze.
Method 2:
Some years ago it hit 11 degrees here in the upstate. The "Week out" park froze solid. Broken pipes all over. the office building was so damaged they had to bulldoze it and build a new one. (Now that's water damage) they also re-did all the park plumbing.. NICE when the park is actually owned by the local greedy rich power company (man made lake runs both a hydro dam and cools an atomic plant)
They put in all FROSTPROOF hydrants.. These the valve is actually feet down in the ground where it never freezes. When you shut off th water flow (A lever) it causes it to DRAIN BACK into gravel around the pipe.. NO freezing happen (Vacuum breaker needed on spigot) again I hook up. fill up. unhook drain.
Side story: The water authority put in way too much bleach one year to sanitize the system. Letting it sit in teh fresh tank for a bit.... Dissapates the bad taste.. Filters help but did not totally get rid of it. TIME did. Only takes minutes.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times