1st Floor Toiler Bubbles when 2nd or 3rd Flushes Toilet

ntl1991

13 years ago

Since I've moved into the first floor apartment of my 3-family, I've noticed that about twice a day, I'll get a large bubble coming up from my toilet bowl. It seems as though this only happens when the 2nd or 3rd floor flushes the toilet or turns on the shower, as I can hear water running through the pipes to go to the upper bathrooms.

The bathroom plumbing is on a "Philadelphia Single Stack" type of setup. The main stack (cast iron) goes through the roof. The main stack is 4 inches. At each cast iron toilet elbow, there is a cast iron vent line that travels up to the attic and ties into the main stack above the 3rd floor toilet.

What could this problem be? I'm think that if there's some sort of restriction in the main stack or the bend at the bottom of the stack where the main drain ties into it to send the waste horizontally through the foundation wall, then the falling waste in the main stack would cause air pressure to build up, which would find it's way to or toilet, where the pressure is released. Is this a proper guess?

Thanks!

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Comments (4)

homebound
13 years ago
No idea, but here's a link for some general reading on that set-up:

Here is a link that might be useful: Philly Single Stack
brickeyee
13 years ago
"What could this problem be?"

Blocked vent line.
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ntl1991
Original Author
13 years ago
Could it be in the main 4" vent through the roof? I wouldn't expect it to be in the smaller 1-1/2" vent lines that run through the walls and up to the attic where they connect back into the main stack... Maybe a birds nest?

I was thinking about having a plumber come by and run a scope through my mouse to the sewer, along with cleaning the pipe walls out to the street. It seems like it would be a smart $250 investment to be sure everything is in tip top shape...
brickeyee
13 years ago
Outside of out and out holes in pipes or roots in the line it is actually pretty hard to judge condition from the inside.

You can find 'bellies' (low spots that do not drain) and blockages, but the line could be leaking at the joints and you are very unlikely to see it from the inside.

If the vent is blocked you are only going to see it if you feed the camera down from the roof (and manage to enter the blocked vent0 or up from below (and manage to enter the blocked vent).