Could a blocked stack vent from a new roof cause burbling bath/toilet leak?

I've got quite a saga here so I"m going to try to break this down in a succinct timeline so that all of the details are present. Please feel free to ask any questions to help me understand the situation because we're currently left with thousands of dollars of damage and we're trying to see if it is clear what may be at fault (if not just bad luck). This is a house that is 110 years old but has had all iron pipes replaced with PVC (except the iron venting pipe going from second floor to roof).

*In January 2020*
We had our roof completely replaced. I'll get back to why this is potentially important.

*In May 2020*
We began to hear a burbling noise in the tub of our second floor bathroom when we flushed the toilet. We called out two separate plumbers that said the toilet and tub shared venting and that the venting just wasn't appropriate (even though, we haven't had this issue in the last 60 years). I noted that the roof replacement could have left a blocked vent but neither company was willing to run a snake down the vent to look for blockage. Both plumbers said "This is just an annoyance sound, there are no problems. But, we can't really diagnose the problem without opening up the wall and inspecting everything.

*In July 2020*
We noticed that there was water damage on the kitchen ceiling directly below the second floor bathroom toilet. We had the initial plumbing company come out and confirm that there is a leak from the toilet (likely a wax ring issue) that is leaking from every flush. We've since had a restoration company out to look at the damage and found black mold from the leak in our kitchen ceiling drywall.

*Today*
The initial plumbing company is coming out to pull the toilet to determine if the problem is the wax ring or a flange issue. Also, the roofing company is coming out to confirm that they did not leave anything to block the vents of the roof. Likewise, the restoration company is out to demo part of the kitchen and remove all damages.

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I know we will find out more information throughout the day but I'm curious if there are any specific questions I can/should be asking to determine if there was some negligence along the way that could move the responsibility for the damage to another party... or if these events were all unrelated and I've just been a victim of bad luck. I appreciate any and all advice or suggestions as we're trying to navigate these problems—and please accept my apologies if this doesn't feel appropriate for this forum or I didn't include enough information.. we're just trying to figure this all out as newbies. Thank you!



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The answer to the first sentence is yes.
In July 2020...most likely the wax ring. Toilets must be set solid with no rocking or movement or the seal at the bottom of the bowl to the floor is compromised.
You must remove any wall or floor coverings to completely remove any mold.
Upstairs bathrooms or kitchens always present a challenge for leaks and these fixture must be monitored continually.

Yes, a blocked roof vent could cause burbling noise, but shouldn't cause a leak. Only a bad wax ring or supply would cause a leak. Too bad the second plumber didn't suggest to video the vent to find the cause.

The plumber has come out to fix the leak—it was definitely the wax ring. Still waiting to hear back from the roofer to come out and make sure they didn't leave a cap or something on the vent. The plumber mentioned that the pressure from a blocked vent could have caused the ring to fail more quickly.

Not that internet and co-workers are always a great source of wisdom but both did mention that a bad wax ring could cause burbling. Does that seem like something the plumbers should have suggested as a possibility or is that correlation highly unlikely?

If the roof vent was capped by the roofer during your reroof, I find it difficult to explain why between Jan and May you had zero problems. Can you go up to the roof and look? If they capped it you can see it on the top of the vent. If they stuff something like a sock or rag to block it that should be very close to the top, shine a flashlight down.

Unfortunately, our roof is very tall and has a steep grade, which leaves it in accessible for us safely (and perhaps why neither plumber was willing to go up and take a look). We couldn't see a cap from the ground level so I guess we may be stuck leaning on the roofers to give us an honest response when they are out.

If u are unsure whether to trust the roofer hand him a long garden hose and ask him to stuff that hose into the vent, then you can turn water on from a hose bib below, if it's blocked water will back out of the vent. If it runs for a few minutes without backing up then your vent should be fine.

That's always something I try to get my technicians to do, and so often it gets lost. Visual documentation makes things so much easier later.

Just to follow-up and close the loop here: we were finally able to get a plumber out with a snake that identified a complete blockage in part of our venting. We were able to open up and investigate the blockage, which was from shingle and other roof debris.



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