I have a 2016 Cruiser Aire. I can verify that it goes up through the wall in the bathroom behind the toilet. I tore into the wall to run solar wiring down beside the vent pipe.
We found it. The original owners of our camper (we're the 3rd) glued and screwed it down so it wasn't venting properly & it had a clog a few inches above the tank opening. We got it unclogged and have a new temp cap on until we can buy the 360 siphon vent cap.Thank y'all for helping us find it. We don't have deadly levels of fumes anymore. Now I just have to get have to get a D series A/C unit fan because we had a B series fan. Thank the gods it didn't tear up the coils