I manage a bunch of rental properties, and one of the properties is complaining of sewer gas smell. I smell it too upon inspection. It is in a sort of hallway section of a master bath. Along one side of the hallway is the walk in shower, the other side is wall with a doorway to a walk in closet. Right in this hallway is where I smell it most. Occupant complains of it in the closet most, which is open to that hallway.

At first, I found 2 AAVs that were not sealing properly, was skeptical that this was the source, but asked for feedback from that fix. The smell returned.

Owner tells me that this doorway from closet to hallway area wasn't there, he cut it in when remodeling. There were a couple of vent pipes going through there, which were routed around the new door. This was decades ago, but it does indicate that there are vents right in the area where we smell gas.

I've checked all the traps (the never use the jacuzzi tub, so thought maybe the trap had just dried out), AAVs where applicable, and all toilets (2 near this area) are firmly mounted to floor with no wobble whatsoever to indicate a broken wax seal. There is laundry nearby as well, with a standpipe drain that I can't see the trap for, but I got no signs of sewer smell from the standpipe.

A new wrinkle today, after a rainstorm last night, the basement was flooded. Around here, our sewer and storm water are in a combined system (yeah, dumb), so if we get enough rain, sometimes you'll get sewage backing up into basements. I don't know if the two are in any way related, but thought I'd mention it. We're going to have the main line snaked to be sure all is clear in the line, but could a backed up line be causing sewer gas smell in one location 2 floors up? Doesn't really seem like it.

Thanks for your help