Vents from the septic tank run back up through the house and exhaust on the roof. If there is a leak inside the house in the vent, or a joint in the vent, it causes our problem.
Actually, it was the ABS plastic. This house was built about 14 years ago, right about the time construction contractors were switching from PVC to ABS. However, the ABS was found to deteriorate, after ten or so years, and cause problems like our septic-vent leak.
After the one plumber, Jason, spent an entire day trying to find the leak and failing, Hubby did a ton of research, both on our construction plans for the house and about the ABS and found out what the problem was, and where it was. That was why the plumbers were able to fix it at all.
The plumbers ripped up quite a bit of the ABS, found the place where it was leaking, and replaced it all with PVC. Then they sealed the ABS/PVC joints with Neoprene and stainless steel bands with worm-gear screws.
The [cough] “aroma” has returned to normal (no septic-tank gas), and the repairs should not leak again in our lifetimes.
If your house was built before 1999, you should be all right as well.
I laid down hundreds of feet of SOLID ABS sewer system back in the mid-1980’s, and I never heard of the solid ABS pipe breaking down except from prolonged exposure to direct sunlight. You’ll find that cellular core ABS pipe exposed to UV from the Sun does eventually deteriorate, but only if it is left unpainted.
The black color of ABS pipe comes from the carbon black UV inhibitor that is part of the material, so it is very resistant to UV even if left exposed, and unpainted.
AFAIK, Building Codes typically prefer (if not outright require) SOLID ABS sewer line to cellular core ABS, and they usually require that any roof penetrations have a thorough coating of paint.
If your problem child wasn’t exposed to UV, the deterioration was likely due to another cause; maybe material incompatibility as might be encountered trying to glue ABS pipe using PVC solvent, or the other way ‘round.
Glad you’ve got it beat, though.
Thank you for your comprehensive response.