I just built a new restaurant, and we noticed since we've opened the men's bathroom smells like sewage. We've had multiple plumbers come out, and it seems nobody can figure out or give me a reason where the smell is coming from. The plumbers blame the construction crew and the construction crew blame the plumbers. We've had the vents checked on the roof, but it just seems like the smell will not go away. What is the best way to figure out this issue. Any advice would be appreciated.

the most common areas would be the floor drain or the wax seal under the toilet/s.
give us a list of what tests the plumbers did to locate the leak and we can possibly add to that list.

Is the trap seal on the floor drain dry?.

How about an AC condensate drain line dripping into an open sewer branch behind the wall and there is a return to the AC handler that pulls air from the same wall cavity and blows that into your bathroom?



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It’s time to call around to find a plumber who can perform a smoke test. This is done by capping off all the vents on the roof the using a smoke machine designed for this application filling the DWV with the smoke.

It may be due to a dry trap or damaged drain line.

It could be due to :
A blocked vent.
A damaged drain line.
A dry trap.