To the "Pineapple Kid":
I am glad you fixed your're problem..... really, I am. That sounded like a bummer, BUT, your words somehow did not explain to me the FIX!
The smell was getting to inside trailer at "vent pipe connection" at tank, inside wall, behind toilet, and below floor?
Maybe someone else will give us an input. I'm 75 yrs old and my my mind is not as quick.
Opps..., after posting, re-read story. The "COUPLING" was "none existing", pipe popped out of tank connection. Okay.... get it.
Famous line from movie "Cool Hand Luke". "Gotta get my mind right Boss."