Hey Mike that's one dingy looking roof
But when I visited your photo page your Airstream is shining like a mirror and lookin like a million bucks!
Gotta be one of four things;
*two different trailers.
*roof photo was a before and photo page pix an after.
*your neighborhood had a bad acid rain storm.
*you're afraid of heights.
Are you in the Klein area?
Have any room for an exclusive Airstream storage lot?
Could call it the Airstream Ranch.
Hopefully Inland Andy will clarify your vent question. but I have read much about a rubber gasket under the pipe cap/cover you photoed needing replacement every 4-6 years and being the biggest source of unexplainable leaks.
Thats a good question about caps for the vent stax. I guess rain that enters the stack must end up in the holding tank eventually???
I think the leak problem is from water that enters around (but outside) the actual vent pipe, through the exit hole in the alum roof. The water then travels to anybody's guess where and finds its own exit where it is not welcome.