Stumped with sewer smell

[Cassix]

Im trying to figure out this customers sewer smell problem. Background is his downstairs bathroom is periodically getting sewer smell coming from his shower is where they mostly notice it after a shower. The bathroom is all tile sitting on a slab so theres no way to get to it. It didnt start until they remodeled the upstairs bathroom. They didnt touch the downstairs during the remodel. They have a studor vent downstairs but looked fine. I checked all p-traps and they are good, the toilet is caulked all the way around so its not there, I didn't check the sewage ejector I'm not even sure if there is one. The home owner wants to do a smoke test but I'm not sure how to even do one. Can anybody give me some pointers on what to look at next cuz I'm stumped

 

[CT18]

Did they change any of the drain layout during the upstairs remodel. Are you sure the studor is working correctly.

 

[Cassix]

Yes studor vents are working and when they remodeled the upstairs, the downstairs wasnt touched

 

[breplum]

Smoke test.
Hire a leak-detection company who owns the equipment.
Not worth the investment in smoke testing equip. for rare need.

 

[frodo]

depends on your house lay out
you might have a down stairs vent that was cut off in the wall, or between floors during the remodel
smoke test the system
go to a supply house and buy some smoke bombs
drop it down the kitchen sink vent...cap the vents

 

[CT18]

Yes studor vents are working and when they remodeled the upstairs, the downstairs wasnt touched

Not saying they touched the downstairs but did they change any drainage during the remodel. They may have tied in a new drain that may have effected the venting below