Sewage vents on 21BHS

[FastEddieB]

A Harvest Host gave us a "360 Siphon" vent cap,  saying it helped a lot with odors.

I'm in the process of replacing the existing cap which, by the way, fell apart as I removed it.

I've never been up on the roof before, and see there's a vent at the very rear - which is the one that fell apart, and another in front of the bathroom vent.

Anyone know which goes to where?  I'm betting the rearmost one, which needs a new cap anyway, is the one for the black water but I don't really know.

As an aside, I tried to post a couple photo via Flickr, but this morning I don't seem to have an option that was there before "Flickr.com", which let me dig out embedded jpg links.

[Diversteve]

The nose knows which is which.
 

[FastEddieB]

Yep! The rear one passed the smell test!

I'm guessing the front one is for the gray water?

[Merlin]

On mine it's rear black, front gray.  I assume the same for yours.