Smell with fan on - 2009 Journey 39Z

[HollywoodGT]

I just developed a smell when running the bathroom fan sucking out. I heard tat you need to open a window to stop back pressure. For a few days I tried with a window open and it wasn't there. Today with the main door open it started again ?

[Eagle5]

Hi HollywoodGT,
I would think the forward cab heater & air conditioner would provide enough venting to allow for a bathroom fan, with a well-sealed toilet. I would suspect that the wax seal at the base of your toilet needs to be replaced.
Eagle5

[creativepart]

Also, a gray tank can smell nearly as bad as a black tank inside your RV. Many RVs have a bathroom sink drain vent under the sink that can fail to do it’s job and let gray tank smells into the bathroom with the vent fan on.

It’s worth checking.

[Morich]

As mentioned Grey can smell pretty bad! It has the air admittance valves at each sink if we look under and often there is a pipe running up with just a strange looking fitting on the end. That valve can stick open or closed at times as it is pretty lightweight, funky stuff. If open it can let fumes comes up but if stuck closed it can make a vacuum as water goes down the drain pipes and the water can get sucked out of the trap under the sinks.
Maybe worth a check to see if you can tell there is water left in the traps as that works to seal fumes coming up from the tank?
Also do I see a washer connection where water may be dried out of a trap to leave it open if not using a washer? Might be worth checking for a pipe that is open if no washer installed?