Bubbles = bad ventilation, right?

I've got a 1st story toilet which has air bubbles on every flush. It does not bubble after/before and water is not siphoned out/in when other plumbing is used.

I'm in the middle of re-doing my 2nd story bathroom right above it, so I thought this was a good opportunity to determine if poor venting was the issue behind this toilet I inherited. I am at the stage where all of the plumbing in the 2nd story is removed. After removing my old plumbing and seeing how small and clogged the air vent used to be, I really thought that would've been the culprit for my air bubbles. I have the stack temporarily running straight up and out of the roof right now.

So, as of right now there are 3 drain pipes running into my entire stack: the kitchen sink, the 1st story bathroom sink, and the toilet. That's it. That stack goes right up and out of the ceiling, in new piping, that I know is not obstructed with anything.

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The toilet is fairly new so I doubt there's anything obstructing that or in it. My only guess is that because the kitchen sink + bathroom sink are vented off of the same stack and the toilet is further down, they are somehow diluting the air the WC should get. From what I've read, I thought the sinks should have venting but this is what I inherited. I put a studor vent on the 1st story bathroom sink when it was replaced which helped the sink drain but never really addressed the air bubbles in the toilet.

Now that I know my actual stack vent is opened up, what would that be a reason for the air bubbles? Could it actually be the toilet? Is the 1st story plumbing improperly routed and not vented correctly?

Many thanks!

  • Could you better explain your bubbles. If nothing else affects the toilet i would be looking at the tank. But it is not clear what you are asking. – Ed Beal Feb 25 at 17:14
  • When I flush, bubbles come up from the bottom of the bowl as water is exiting the bowl. No bubbles before or after. If I slowly pull the handle and open the flapper slower, there are no air bubbles. – RCNeil Feb 25 at 17:24
  • That sounds like the wax ring may be blocking the flow but some sort of restriction I would agree. – Ed Beal Feb 25 at 17:48

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