Is this the gray tank vent in the bathroom vanity?

[Steve Morris]

Like @csevel I've been tracing down a faint sewer/sour odor. One place I wanted to check was in the vanity to see if I have any leaks or loose pipes under there. So today I pulled off the bin on the front. Fortunately, everything is tight and dry. All the joints are glued and I checked all couplings to make sure they are tight.

But while I was in there, I wanted to do a test fit on the alternate shower components that I bought back in May after looking at Mike's  @mossemi system. Much to my surprise, there is a block glued to the inside of the cabinet with what appears to be a check valve and two PVC pipes going to it. Is this the gray tank vent? Or is there one on the fresh water tank? I thought the vent was under the kitchen sink. Mike's trailer is a fair bit older, and didn't have anything mounted there.

If it is a vent, any suggestions on how to check to see if it is functioning properly, and not letting smells from the tank get through?

Claudia, did you figure out where your smell was originating?

 

[Galway Girl]

That brass fitting is the vacuum breaker valve from your black tank flush.  One pipe comes in from the black flush hose bib inlet on the street side of the trailer.  The other side runs back to the flush head on the black tank.  It’s auto draining so the black tank flush line won’t freeze. 
 

The part is in a kit as the Swan San-T-Flush SFS150. 

In the diagram from Oliver it’s the red square on the left.

 

 

I also remember having a smell once because we hadn’t used the shower and the grey tank odor came up the dry p-trap for the shower pan.   We put a couple cups of water in and no more smell.  

Edited October 11 by Galway Girl

[csevel]

I spent some time under the sink trying to locate any loose fittings and found nothing.  I did find out that the black tank from under the dinette seat was a contiguous open area (which I simply did not know) so any smell I had under the dinette was in the sink area too except not as pronounced.   I decided to just leave well enough alone and spray OdorBan everywhere as per Ronbrinks suggestion in my original post, including the valves.  I put some https://bit.ly/3BLgPdG in there and haven't had smell since.   Not sure if warm weather will reactivate it next year but I'm really glad I opened the area up!  I may want to change out my faucet someday, check p-traps etc.. and it was pretty simple to do.   

Thank you for the gasket material you gave me at the rally, however,  I didn't end up using it as I thought it might be too hard to place around the perimeter of the cubby.

I used this instead:  https://bit.ly/3A0quwj   It's channel shaped and easy to route.

Everything went well.  I used the original screws and snap caps even though I had bigger ideas in the beginning.  For the number of times I'll actually go in there, it wasn't necessary to use plus nuts and get all crazy.   So far no leaks and it looks stock.

Good Luck Steve!  Let me know if you find anything more.

Regards,

Claudia