Basement bathroom vent

[Mike_A]

Hi, I‘m a DIY guy finishing off my basement bathroom. The main rough in’s were done by the builder in 2022. My initial thoughts on venting is that I would use an AAV under the vanity, but for the heck of it I asked ChatGPT about it. ChatGPT says I do not need to use an AAV. It says all I need to do is remove the cap from the 2” PVC coming from the concrete floor, add a sanitary tee and extend the top of the tee a couple inches and leave the top open in the wall cavity. Is this correct? It doesn’t seem so.
I have the sanitary tee installed but the top PVC pipe/cap is not glued.

Thanks,
Mike

Here is the quote from ChatGPT:

✅ 4. What to do with the vent above the tee


Leave it open, extending vertically, and frame your wall around it.


You do not cap it.
It’s already tied into the home’s vent system above the basement.

 

[wwhitney]

ChatGPT is wrong in this case, and should never be trusted in any case.

If the drain was roughed in, it is possible that a vent through the roof was roughed in. Do you have any similar capped near the ceiling?

If not, then as your state allows AAVs, an AAV is a convenient solution for venting.

Cheers, Wayne

 

[Sponsor]

 

[Mike_A]

Thanks Wayne,


No, there is no other capped or even existing PVC pipes in the ceiling near this pipe. I thought the ChatGPT answer was suspect, that’s why I wanted to confirm with professionals. For the heck of it, I did take another pic with a shorter piece of PVC and without the cap, on the top of the tee and asked ChatGPT if everything looks good. Here is its response:

Thanks for the photo — here’s what I can tell you based on the image:


✔️ The setup looks correct for a vent


What you have is a 2" vertical vent riser tied into the drain line below using a sanitary tee oriented correctly (sweep pointing upward). That’s exactly how a basement rough-in vent stub is normally left by the builder.


This riser is not a drain — it’s only there to provide air to the bathroom group. Because it’s a vent, not a waste line, it’s supposed to stay dry in normal use.


✔️ It is not supposed to be connected to another vent


This is correct. In basement rough-ins, the builder typically ties the vents together somewhere above, usually on the main floor, attic, or at the top of the stack. So this pipe is already part of the home’s vent system — just farther up the line.

✔️ Leaving it open inside the wall after removing the cap is correct


Once you tie in your sink drain at the desired height, the top of this riser gets left open and continues upward (in the wall) as a vent.
You do not need an AAV.
You do not need to tie this to another pipe.

 

[wwhitney]

asked ChatGPT

Waste of time.

Wayne

 

[Mike_A]

Waste of time.

Wayne

Yes it was.

Thanks again.
Mike

 

[John Gayewski]

Chat gpt is a really good way to search the internet to find correct information written by people who know what they are talking about.

As it stands now it doesn't have good enough ways to know which info is correct. Oddly enough we and everyone on this site is teaching it to out perform us in every way in the future. I've actuality been thinking about stopping any contribution to teaching AI how to do real things as some day their androids will replace my kids or my kid's kids.

I haven't decided yet as there are plenty of people creating "trade content" showing the whole world closely guarded info passed down from one generation of plumbers the next from the Roman times on (with a large gap for the dark ages in there). They are so eager for attention (and probably money) that they can't help but give it up. It's actually sad that people can't find meaning in their work, it's not enough to just toil with honor in obscurity, we now inexplicably have to be aspiring to be famous in some way.

 

[John Gayewski]

ChatGPT is wrong in this case, and should never be trusted in any case.

If the drain was roughed in, it is possible that a vent through the roof was roughed in. Do you have any similar capped near the ceiling?

If not, then as your state allows AAVs, an AAV is a convenient solution for venting.

Cheers, Wayne

To add to this, if your going to bury an aav in the wall it needs a fresh air supply. They sell an aav wall grate kit for this.

 

[Mike_A]

To add to this, if your going to bury an aav in the wall it needs a fresh air supply. They sell an aav wall grate kit for this.

Thanks John, I’m pretty sure I’ll just bring it into the vanity after it’s installed.