A plumbing mystery...Main line backup?

[RyantheNeophyte]

I've had a problem for some time, and i'll recap the best I can:

-owner in an end-unit of a string of 4 condos (built in 2006)
-plumbing system includes usage of AAVs
-2 stacks, and a shared vent that releases above one of the other condos
-condo is 2 stories, and includes a basement

Issues:
-Since 2011, toilets gurgling- sometimes without any other water appliances running. No other issues until late 2019. The gurgling initially occurred on the toilet on the main floor (tied to Stack #2) as well as one of the 2 bathrooms upstairs (Stack #1)
-December 2019 we had our first leak from our floor drain. Company#1 determined it to be a main sewer line flush that was needed, so we did that. They ran a camera, checked the clean-out, etc. Nothing else in particular. We believe the washing machine on basement floor was running at that time.
-Soon after, the gurgling returned but no immediate issues.
-January-February, minor flooding out of our drain pipe again. Toilets gurgled and, when flushed, water would stay and very slowly go down. The washing machine was running, but no other major activity. Company #1 (a well-known firm) came, which included a group of 5 individuals, and they walked out telling me they couldn't help me. I toyed around and was able to create another leak by running the washer- although this may not be pertinent (perhaps any major appliance would have set it off by then).

Company#2 came, identified a very noisy AAV and how it was likely not working. I don't believe he did anything down the pipes other than check the clean-out. I replaced 4 AAV's.

-The problem seemed to pass (without intervention), but i noticed the toilet still gurgling soon after.

-One factor of note during these incidents so far- the element of time delay between the occurrence and the plumber's arrival

-3 months later, starting in May of this year, we had a collection of about 10 minor floods out of the drain pipe in a 3-day span. The toilet upstairs had the same symptoms, however the toilet linked to stack #2 was fine (and has not had a single problem in months). By the time the plumber arrived, we could not run ANY water tied to the main stack (#1) without almost immediate flooding downstairs. Visit #1 by Company #2 included snaking the clean-out which he said had standing water. He ran the kitchen sink for a while, no issues, no flooding. We did not think to test upstairs for some reason. After he left, we were able to run the kitchen sink and 1 load in the dishwasher, and then gurgling and flooding occurred again. We were once again unable to touch a water appliance (except for bathroom on stack #2). As soon as we ran something, water would spill out of the floor drain, including what looked like toilet paper. Mostly clear water beyond that, and never in an amount more than we were using.

A couple pieces of information during this phase that may be relevant:

-After the first couple floods i decided to replace the AAV i had missed (in the kitchen). Upon removing the AAV, the toilets upstairs (which had been filled to the brim) dumped and a had another flood. I suspect that's just a product of gravity and negative pressure.

-After the plumber had left (and before the flooding had commenced), i went to the upstairs bathroom. I ran the sink- and the toilet gurgled immediately. I took a 2 minute shower- and the toilet gurgled the entire time.

-I see no issues with the AAV pipes being set to code, etc.

-No other neighbors appear to be having problems

-Company #2 came back a second time, snaked from the second bathroom upstairs, and so far, we have been able to run water since. There have been no notable issues- except that the toilet upstairs has gurgled a couple times since...

I'm hoping to isolate this problem to a possible main stack issue, and hopefully get a serious response from my condo association. The last plumber suggested it was a clog (and we are now treating with a safe product to help clear the lines), but I don't necessarily agree unless we had multiple clogs. If we had one above the main floor, then why would the washer (which is 8 feet from the cleanout in the basement) trigger flooding as well?

Hoping for some advice. This problem cannot continue. We don't put anything down our drains, so I don't know why this has become so incrementally bad in the past 6 months...

Ryan

 

[Terry]

Hi Ryan,
Has anyone run a camera down the main line that is having the issues? It sure sounds like a main line problem. The condo, built in 2006 is now 14 years old and there could be settling of the lines, perhaps a low spot that was not there before. The washer at some point also ties in, so having that add to the problem is not a big surprise.

Nobody puts anything down the lines? Common things that are problems are flushable wipes. They should never be flushed. Toilet paper will break down, but wipes don't. The people that come out, what kind of snaking equipment did they use, if any.

A floor drain doesn't flood unless you are having serious problems, and it's not the venting.

 

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[Jeff H Young]

Drains are clogged, on underground , You need to see the video inspection. Could be pipes dont have proper slope . where does sewer go after exiting condo? Private sewer serving the other buildings?, out to street? Main in street clogged? could be a lot of causes there are a few

 

[Jeff H Young]

Terry put it better than me just minutes befor me . Totaly agree it aint the aav its something like Terry and i said and yes one moron homeowner can cause it because they think anything is flushable and then it finds a spot thats not quite perfect and lays there stuck until something else comes along and presto you got the gurgling etc. sometimes it will wash clear and problem goes away on its own but comes back. Anyway like I said could be a lot of things . You need to hire a pro perhaps company 3 Im not there cant tell you they all are incompetant or not but its continual . its going to cost money to figure out no free estimate on this its time and money .

 

[RyantheNeophyte]

Thanks so much for the replies, it's great to hear from experts and those experienced in the field. Responses to your feedback:

-we had a camera inspecting into the main sewer line in December, which is when they flushed the sewer line. I'm the end unit, with the sewer line running away from me. there's an access point on the opposite side of the condo furthest from me. During that camera inspection, no one footnoted any odd debris in the main line, just that it was a bit cruddy.

-It is definitely possible that other neighbors are putting things down the drains that don't belong- and i'm the end unit who is first to suffer. I know in our household we're very careful about that. We're careful about what we flush- it's just the wife and I, which helps.

Thanks so much for reading such a long post. I'll pay attention through the clean-out (and maybe even buy an inspection camera) to help identify problems when they pop up. The problems aren't always at their worst by the time plumbers make it out.

Thanks again!
Ryan