Many plumbing-related queries could be answered by understanding the Trail Manor plumbing setup. There is a plumbing diagram in my
Bill's Tech Stuff album. This diagram is quite old, but I don't think there have been any meaningful changes since it was first drawn. For example, it shows the anti-backflow valves that keep the water where it belongs. It shows why a water-heater bypass is not needed. And it shows what the drain valves under the trailer do.
https://www.trailmanorowners.com/for...&pictureid=435
Questions not answered by this diagram can be asked in the usual Plumbing forum, as always.
Bill