Black tank odor. A well designed system shouldn’t smell. And ours doesn’t……99.9% of the time. Once in a while when it’s windy, or when driving I suspect a down draft happens into the vent and puts pressure on the tank…. (I verified that the vent is in fact working so that’s not the problem) and said pressure burps out somewhere. The most likely candidate being the seal on the ball valve in the mid-toilet. This is a weak spot and requires occasional cleaning. If you put water in the toilet and it leaks down it’s not sealing. Turn off the water, don a latex glove, take a paper towel with a healthy dose of Soft Scrub and clean the seal ring the ball rides on. Anywho, our odor disappeared rather quickly, which made it a hard problem to diagnose. So I came upon a vent that claims to always maintain suction on the system. Up on the roof I went. Two vents….hmmmm. Call below and had someone flush…. sound gave it away, the rear one.

Proceeded to remove the Dicor sealant. Note the screws torqued down so as to crack the fixture in several places. No points there Forest River.

Then the vent cap. Pipe was a little askew, and that’s after they drilled the SECOND hole…. oh well.

Glued the vent on to the pipe….

And re-sealed…..

We shall see. I will report back here.

As an aside, the sealant coming off was still nice and flexible. And, while I had the gun out I checked all the other sealant on the roof…. But it was all in good shape.

UPDATE: after one year all concerned agree….. this works and we have not had ANYMORE whiffs….. I would definitely do this again.