Plumbing vent roof penetrations-'70s vintage
On my 70's vintage trailer, the plumbing vent pipes come up through the roof, through a rubber "gasket", and into the pot metal chimney/protector. I just replaced the rubbery gaskets, and as I haven't reinstalled my interior skins yet, I can see that I am getting leakage in a hefty rainstorm through this assembly. I have a hole cut in one gasket with a vent pipe going out of it, and the other is currently just a blank piece of rubber with no hole. Both leak. My understanding is that this set-up allows the pipes to move as the rest of the shell is rattling around on the road, and so you wouldn't want a "hard" connection of the pipe to the shell with a more capped metal vent top.
I have seen the little mushroom shaped vent tops that several forums members have put on their trailers, but the question is, do you still use the rubber gasket set-up, or a hard connection from pipe to metal cap? Also, How are the modern trailers built? This seems like a very marginal, leaky, and maintenance intensive design. I am sure a good portion of my rear floor rot was due to this design.