Sewer smell, not sewer
Recently had this happen, and figured I'd share to maybe help someone else down the road.
We were out camping at a location with full hook ups so we had sewer hooked up. During the trip we were occasionally getting whiffs of sewer smell / rotten eggs. Couldn't see an obvious answer, and just decided to keep an eye on things.
Next trip a week later, at a campground with no hookups, and we hadn't even used the bathroom yet, we once again got occasional smells of sewer. We moved sites the following morning to be closer to family for this family reunion we were on, and for a bit no sewer smell, then once again, hit us again.
I started poking around the basement area, again looking for any signs of leaks with no apparent solution. That is when I heard the fizzing sound....
Turns out our battery (which I knew was on its way out and was planning to replace in the next month or so) must have boiled off most of the distilled water and the sulfur aka rotten eggs/sewer smell we were getting whiffs of was coming from the battery box vent holes both on the front and underneath the trailer.
A simple turn of the switch to kill charging to the battery (we were on shore power anyways) stopped the issue and we enjoyed the rest of the week vacation without smells/incident.
So there you have it. If you smell sewer, and can't find a sewer issue, check your battery!! Hope this helps someone.
5th Wheel: 2013 Denali 262RLX
Pull Vehicle: 2006 Chevy 2500HD Duramax, CCSB
Hitch: Reese 16k