# Air Admittance Valve in Basement Bathroom



## John Callahan (May 22, 2012)

New to the forum and appreciate any help. 
I am installing a full bath in my basement. As seen in pic I have a 4" cast iron vertical waste stack that goes to outside of house and also horizonal under slab along basement wall. I want bathroom to start a couple feet from stack and in this order from stack; Toilet, Sink and Shower. Where in this configuration do I put the Air Admittance Valve? Thanks so much for any advice.


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## jaydevries (Jan 29, 2012)

how far away is shower trap from sink.
also what is on the horizontal and vertical stack


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## John Callahan (May 22, 2012)

The cast iron stack is connected to a full bath on the next floor. The horizontal run from the stack under the slab in the basement is connected to a washer drain and floor drain only. The stack vents to a 3" pipe through the roof. Vent is hard to access and also I dont think it can handle the new full bath in basement. 

Thanks!


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## jaydevries (Jan 29, 2012)

how far from sink is shower going to be?


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## John Callahan (May 22, 2012)

Toilet, sink and shower will be in line (next to each other) at just a little more than minimum code requirements.

Thanks


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## jaydevries (Jan 29, 2012)

depends on code if you are worried about it. i would put aav under sink and let it be a wet vent for shower and the toilet is fine


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## John Callahan (May 22, 2012)

Jay, 

I am curious why the aav would be at middle fixture as opposed to, say at one end of the branch? I don't do much plumbing so I just dont exactly understand why the sink? Is it because the trap for the sink is the highest trap in the branch?

Thanks for your help!


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## jaydevries (Jan 29, 2012)

it would be like running the vent straight up and arming over to catch a shower then continuing up to catch sink with a t then vent going up through roof . also sink is highest fixture . you could put one for shower and then another for sink. toilet is self siphoning so it well drain through vent stack


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## John Callahan (May 22, 2012)

Jay,

Sincere thanks for your expertise.


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