When you get your trailer, it will be "winterized". That means anti-freeze in all the plumbing. At the time of the walk through, there will be a chance to play with this or that. Running water through the pipes will mess with the winterization. So, what to do:
1) Don't play with that stuff.
2) Re-winterize after you have played
Why bring this up? It's worth thinking about ahead of delivery ....
One recommendation is to "camp out" at the dealer in your new toy. Things you find that evening can be addressed in the morning ( questions or issues ). There will be questions ... After that's done, the dealer probably can re-do the winterization.
We got our van at the same time of year. We opted to not mess with it at delivery. That's also a valid answer to the question.
The only wrong answer to the question is to not winterize and have the trailer stored / unheated / getting ready for a trip out in freezing temps. Since it's already into the 30's at night in Michigan vicinity ( I have data on this ....
) freezing temps in November are pretty much a certainty.
Common wisdom is not to head out on an 8 week trip in an "untested" RV. We took off for 6 months with our new van. Worked out ok for us. Do as I say ... not as I do