Deborah,
As noted by Ray, please have the RV dealer do the first winterizing of your unit. Also, have the dealer to exercise the 3-way valves in your presence so that you know that they are working properly. The 3-way valves, in the UDC, as supplied on a lot of the RV's have a problem with the plastic handle not rotating the valve stem. If there is a problem, let the dealer take responsibility for the repairs or replacement.