I have a good friend (who lurks this forum) who has a '06 MKO wrote to me on kinda of weird situation where he had a water leak from the underbelly and it turned out to be a leak under the bathroom sink!!! I'll let him tell the story. Thought I would share just in case one of you ran into it and help save you some time and trouble. We need to share our experiences and help one another out. Here goes....
I thought we had a leak last week from the black tank flush because water starting dripping from the underbelly when we ran the flush. When I took down the plate in the middle of the belly cover under the tank/interior dump valve area, I could not find any leak, but could track water running down the water line. AFTER I unloaded the basement (I'm sure you already see where this is going) and searched unsuccessfully - I did finally find the water was coming from under the bathroom sink. The line in from the side of the trailer into the vacuum break was loose, just a quick couple of twists of the screw-on connection and everything was fine. It was dripping back down the exit line from the vacuum break back down to the tank rinser, so it didn't really leak inside, just ran down the line, dripped onto the underbelly and then on the ground. I left the panel off for a day to let the insulation dry. If I had looked under the sink first it would have been a five minute job, not an hour spent unloading and looking.
rockin's notes: Lesson learned, on a water leak - start your checks high and move down as you go.
If you could see this guy's basement.....that was a major under taking!!!! Now that's mean, right there. I'll pay for this one!

P.S.S. It's no wonder nobody invites me over to take a peak at their rig....it get broadcasted all over the web!!!

Now I get it!!