Plumbing luddite here, first-time condo owner with a problem that's developed in last 2 days. I live in a top floor unit and my bathroom shares walls (and I assume vents/outflow pipe) with two other units' bathrooms. Whenever I hear a neighbor running the shower, after a while big bubbles start coming up in my toilet bowl, from the sewer side (not the high pressure water input). Then the bowl level starts to fluctuate, going down to nearly empty and then partly refilling. This isn't my doing -- I'm not running any water or trying to flush. All my sinks and my bath drain fine during this time.

During these neighbors' showers and for about an hour after, my toilet doesn't drain when I flush or pour down a bucket of water. After a while though it starts to drain slowly on its own and after an hour or so I can pour down water to get a full, normal flush. (I've turned off the toilet's water intake for now.)

I ran a snake down the toilet (mine goes only 3 feet) and found nothing. I should also add that twice now during neighbors' showers I've had a little backflow come up my shower drain, <1 gal. I posted a note and asked around but nobody else in my building reports any problems.

1) What's going on and, 2) why isn't this affecting anyone else? I've alerted the condo management co but I'm not sure if this is everyone's problem or just mine.

Lining on the top floor makes it more interesting, because you apparently have a blockage in the line AFTER the neighbor's connection, but before it gets to the lower floors. You need a plumber to snake that portion of the system, NOT the main lines under the lower levels. I hope you have an elevator to carry the plumber's equipment up there.



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