Leaking plumbing vent reveals weird configuration.

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dlukas

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I have a 100yo house with 3 floors including unfinished basement. About 5 years ago, I put a bathroom in the 3rd floor--the only plumbing on that floor. I hired someone to do the rough-in plumbing, and did the rest myself. I used Studor vents for that bathroom.

Fast-forward to this year. I noticed that a plumbing vent in my basement (lead pipe) has a hole and is leaking water into the basement anytime water runs in the 3rd floor bathroom, but doesn't leak when a fixture runs on the main floor or basement. Luckily there is a floor drain right next to the leak, so it doesn't have an opportunity to flood. But it leaks toilet water as well as grey water, which is super gross, if not a full-on plumbing emergency.

I did some investigation, and discovered that the plumbing vent ties into the main waste stack about 3' above the floor on the main floor with an upside-down wye. So clearly some of the waste water from the 3rd floor bathroom is diverting to the plumbing vent and then leaking out the hole in the basement. The system was clearly never designed to have plumbing on the 3rd floor, and I guess the guy I hired to do the rough in either didn't notice this when tying into the main stack, or he figured he would be long gone by the time I discovered the problem.

So now I'm trying to determine how to solve this. Here are the options I can think of:
  1. Just repair the leaking vent pipe in the basement and be done with it. It worked fine for almost 5 years until the lead pipe started leaking, so maybe it will keep being fine after the leak is repaired.
  2. Where the vent ties into the main stack, replace the upside down wye with a right-side-up wye. This should prevent any wastewater from diverting into the vent. And I think this is how it would have been configured if the house had been designed from the beginning to have plumbing on the 3rd floor, but maybe I'm wrong about this?
  3. Replace the wye with a straight coupling, extend the vent pipe up into the 3rd floor crawl space, and put a Studor vent on it.
Option 1 involves jackhammering concrete; options 2 and 3 involve cutting 4" cast iron pipe. And option 2 involves trying to replace fittings in a very tight space with respect to the framing of the house. I don't love any of these options, but I want to pick the option that ensures I only have to deal with this once.

Thanks in advance for any wisdom you can impart :)
 

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frodo

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I can not tell anything by your pictures. BUT if the vent from the 1st floor is tied into the waste on the 2nd like you show in the meme
then the vent needs to be run up and out through the roof
or..tie it into a vent on the second floor
 

dlukas

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I can not tell anything by your pictures. BUT if the vent from the 1st floor is tied into the waste on the 2nd like you show in the meme
then the vent needs to be run up and out through the roof
or..tie it into a vent on the second floor
Thanks--that makes sense. Where that upside-down wye currently is, do I need to just cut that out and replace with a straight coupling? There isn't really a way to cap an upside-down wye in that spot without inviting future clogs, is there?
 
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