In the "learn something new everyday" area:
I have low point drains in the compartment with the fresh water connections. After owing this coach for four years, I found two more low point drains on the other side of the coach. Surprise to me! We had a combo washer/dryer in the coach, but took it out and put a small freezer in there instead.
As to winterizing, I have used just air in the past, but now, I blow the lines out with air, put pink stuff in, then blow them out again. That makes it much easier when we prep the coach for the next trip after winter breakup.
GM