[bryguymi]

Bryan,

My toilet is in middle of coach and the waste tank is directly under the toilet.  The pipe from the toilet goes essentially vertically into the top of the tank.  In my case the seal between that pipe and the tank was not airtight.  The square tanks that were used on our vintage coaches seem to sag in the middle of the top and this pulls the tank away from the pipe.  It seemed that I always had a bit of a smell.  A little clear silicone around the pipe did the trick for me.

bill

Bill,

So I've looked atop of my holding tank, and ALL of the pipes that are supposed to be attached to the top are loose.  I suspect this very well may be my problem.  Thanks for the direction. 

Bryan