I live on the 1st floor of a 5 story apartment building and I am getting a sewer smell entering my bathroom from above. It's not coming from my unit, at least nothing in plain sight. My P traps and drains seem to be just fine. My bathroom has a low ceiling where the plumbing and other utilities are housed. There is a square hole in the center of the ceiling where there once was an exhaust fan. The fan had been removed and now just has a vent cover over it. It is here where the sewer smell enters the room. The smell seems to originate from the area where the bathtub drain from above comes down. It also could be coming down from where the toilet drain comes down, although that is right by the vent hole that I am inspecting through and it doesn't seem to be that bad there.

Here is my question: Is it possible for a bathtub or toilet drain (from upper unit) to be venting gas and yet not leaking water?

Follow up: If the plumbing vent on the roof were clogged could it be venting in the wall?

Additional: What are the chances that a plumbing vent pipe cracks? I can’t imagine something like that breaking.

One more: Do sewer gases tend to vent more when there is more plumbing activity or less?

What are the chances that a plumbing vent pipe cracks? I can’t imagine something like that breaking

that is what i would look for.

It's common for cast iron vent piping to "rot" or rust out. I worked in a 1949 building in the mid to late 1980s. It had 99 public restrooms, all cast iron-piped. We had a plumber there for over a year, full-time, gradually replacing vent stacks. He was still working on it when I left. I remember this well because he would periodically set off a smoke alarm with his torch.

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Links to the State of Wisconsin Plumbing Code:
[docs.legis.wisconsin.gov]
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I am not a plumber.
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In properties that have congested plumbing (meaning lots of bathrooms or fixtures back to back) they tend to have more issues with sewer odors. Higher use results in more air being forced out of the venting.



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