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Code Context: Colorado. City jurisdiction has adopted the 2018 International Plumbing Code

My house was built in 2015 and stubbed out for a full bath in the basement.

I am now finishing the basement and wondering what additional venting may be required or if the original build being stubbed would have already addressed the venting aspect.

Does that existing 3" stack running up to the 1st and 2nd floor cover it? Or should I add an AAV as shown in red? Or do I still need anything more?

DWV Design

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  • If you don't have a vent pipe up in the ceiling, or coming down from the ceiling, that was evidently not addressed at build time.
    – Ecnerwal
    Commented Mar 7 at 18:22

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Does the 3" stack have (seems very likely given what it serves) any toilets entering it above?

If so, it stops being a vent stack (and becomes a soil stack) below the highest toilet entry, and a separate vent stack is needed to bypass around them, under current codes. As far as I can tell that was not a consideration when the cast iron plumbing in the house I grew up in was installed, but things do change with regards to what's considered acceptable.

Or the AAV option for venting. Looks like you are at least planning to put that high, which will improve the odds for it working over time with minimal failures and replacements required.

Under the likely applicable codes for a 2015 build there should be a separate vent for the first floor powder room sink (and toilet, usually via the sink), due to the second floor bathroom above, which you might be able to tie in to, if it's big enough.

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  • Yes, directly above is a half bath on the first floor and a full bath on the second floor. What I can see from the basement is 3" closet bend for the first floor half bath toilet. A 2" branch going up to the 1st floor sink. And another 3" branch going up inside the wall which I'm guessing is then going up to serve the 2nd floor full bath. So to confirm, it sounds like you're saying the AAV up high in the wall in the basement is sufficient to vent all 3 basement fixtures?
    – crichavin
    Commented Mar 7 at 18:20
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    If it (and the pipe serving it) is of the appropriate size (in terms of DFUs,) yes.
    – Ecnerwal
    Commented Mar 7 at 18:29
  • The Oatey Sure Vent says it supports 160 DFU branch and 24 DFU stack. Not sure what that means, but on the top of the box it says the max DFU on a branch of 2" is 6. They have another chart that shows a private full bath (Sink, Toilet, Shower) as beign 5 DFUs. The vent pipe the AAV will be attached to will be 2". So it seems this AAV should work. Thank you for your help! AAV: oatey.com/products/…
    – crichavin
    Commented Mar 7 at 19:18
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    IPC is very handy, because you can check it out online to understand those details. codes.iccsafe.org/content/IPC2018P5/chapter-9-vents
    – Ecnerwal
    Commented Mar 8 at 1:48

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