I suspect a foul odor in the middle part of my house may be due to a break in one of the sewer gas vent lines running up to the roof. It’s a 70 yr old house & I did find after breaking into a well a rusted pipe & void at one of the thread joints. I put a rubber hub over it & fixed the odor problem in that closet.
However, I suspect another section inside a wall somewhere (2 story house) has a similar problem
Is there any way to trace a break in a vent pipe system without breaking into walls at random points?