Kitchen Sink Vent Problem

[Schubert M]

Hello all,

So I replace part of my Sink drain yesterday. It's was old cast iron and it got replaced with new PVC. I noticed my vent line coming off the Tee was not attached to anything. It appears to terminate in the wall behind my kitchen cabinets. I saw no sign of it going into the attic or out of the roof. I initially assumed it tied into the washer drain vent which is located about 10 feet away along the same wall. The kitchen sink vent pipe was freely moving in the wall and not very accessable. Will sewer gases vent into my wall space. It may have been this way for years and I've not noticed any smells.

I've uploaded before and after images of the repair. The right of the Tee leads to the sink. Top is vent. Bottom is drain.

Thanks

 

[Geofd]

if you have it all tied in or capped off you should be ok

 

[Schubert M]

Im almost positive it's not tied in though. Just a pipe that's open in the wall. If I cap it, won't my sink p trap siphon out and cause odors from the sewer?

 

[Jeff Handy]

This is pbly a quick and dirty and non-code solution.
Put a cheater vent (air admittance valve) on the top end of your “vent to nowhere”.
As high as you can go, above the flood level rim of the sink.
So that water can’t flow out of the vent if the valve fails and the sink drain line is plugged.

The air valve opens and admits air when negative pressure from draining water pulls it open. Helps drain water flow along.
Then it shuts again, keeping gases from getting out.

I am not a pro, and I suspect that closing up the air admittance valve in the wall is likely a no-no.
So you might want to create a hidden access panel right there, for future inspection and servicing of that valve.

Maybe all this would be code, a pro here can jump on and advise.
Obviously, getting a real vent to go up and out of the house is ideal.

https://www.amazon.com/Oatey-39017-Sure-Vent-Admittance-Adapter/dp/B0069KCZO4

 

[Jeff Handy]

Vent lines, and even drain lines, sometimes get left unfinished by mistake.
The drywall guys might have been on schedule to close up the wall, so they did.
Then the unfinished vent got forgotten about.

I had a client who had an expensive house built.
After taking her first shower, she came down to find a flooded living room, and half the ceiling drywall was down.
Plumbers had never finished tying in the shower drain, there was a missing wye and several feet of pipe missing that just got drywalled over.

 

[Jeff Handy]

Also, shouldn’t that pvc drain pipe and tee be 2”?
I think 1 1/2” is ok for vent, not for drain?
Not a pro, so not sure.

 

[Schubert M]

Also, shouldn’t that pvc drain pipe and tee be 2”?
I think 1 1/2” is ok for vent, not for drain?
Not a pro, so not sure.

The main drain below the Tee was 2 inch but the original sink drain was 1.5 inch. I didn't think about making the Tee 2inch. Our sink fixture is low flow so I wouldn't think it would have any issue. Here in Kentucky, AAVs haven't been approved yet but in states where they are, they must be in open spaces or have a wall vent box. Any issue putting it under the sink. It should not allow water to back flow if the drain got stopped up somehow. Is that correct?

 

[Jeff Handy]

AAV valves are installed under a sink in an kitchen island, as high as possible.

But your situation is messy, damned if you do and damned if you don’t.

I don’t know about codes, but it would likely work. Just be aware to check for leaks, especially if the sink drain line ever backs up.
The AAV has a spring operated mechanism, it could stick open then leak drain water if the real drain line was plugged.

Meanwhile, putting the AAV on there is better than leaving it just open in the wall, putting out sewer gas.
Or better than capping the vent, then your sink drain would be slow and gurgley and will be likely to clog from slow drainage.

Best course is to get a cheap snake camera from Harbor Freight or Amazon.
I got one for about $90.00.
They can go about 9 feet up, longer with optional extensions, you can look behind the wall and see if your vent is cut off or maybe it really does go up and out of the house.

 

[Jeff Handy]

The Amazon ad shows it being installed just as you need.
You would have to cap the vent riser in the wall, or gas would go up there.

 

[Schubert M]

That seems like the best work around to me. Thanks for the info!

View attachment 21608 The Amazon ad shows it being installed just as you need.
You would have to cap the vent riser in the wall, or gas would go up there.

 

[Matt30]

An AAV can be installed there and still meet code as long as it’s made accessible. Defiantly better than being left open ended.