Kitchen sink drain vent

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PTMARC

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I am remodeling my kitchen and have a new 10 inch deep stainless steel sink to install with a garbage disposer. The current/old sink drain is too high for the new deep sink with disposer and I am working through options to lower my stub out. The drain currently runs through the stud bays in an exterior load bearing wall. To drill holes lower for new drain pipe would mean weakening these studs to a point that is dangerous....I am trying to find a solution that avoids having to replace these studs and drop my drain straight down into the basement where it could connect into the main drain out. My question is can I use this current horizontal pipe as the vent with the waste drain going straight down? If not any other ideas are greatly appreciated. I am in Virginia and under IPC.
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WorthFlorida

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Terry's take on sink drain height;

There are stud supports sold to brace the studs when holes are drilled. For your job 2-single stud braces and one thriple stud brace.

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wwhitney

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My question is can I use this current horizontal pipe as the vent with the waste drain going straight down?
No, that's not go to work, because the horizontal pipe is too low (it would need to be 6" above the sink flood rim) and because it's pitched the wrong way (your proposed 90 would hold water if it ever go in there).

I suggest you stick with the current layout and just lower the pipe. Cut out the horizontal and the stack low enough to work. You could cut it so that your new san-tee goes directly onto the cut, and then you'd end up with two banded rubber couplings on a straight section above the san-tee, or maybe just one banded rubber coupling if you are able to deflect the free end of the upper vent pipe out of your, i.e. 2" or more.

Then instead of replacing the existing full height studs, just sister them. The cripples only carry the weight of the window itself, so you could skip sistering those, or you can sister the single cripple. The tricky part is that your king stud is very close to the next common stud, so you'll need to sister that with some angled nails or structural screws. Now you can drill a new set of holes for your lowered trap arm.

I was going to suggest reinforcing the studs with Simpson HSS stud shoes, but there's a couple obstacles. One is that the stud bay between the king and the common will be too narrow to access all the fastener locations. The other is that they don't make one for a quadruple 2x, they stop at a triple. You could cut out the lower portion of the cripple against the jack, as it's doing very little, as long as there's no siding attached to it, or you can deal with the fasteners poking through.

Or your other option is to rely on an AAV for the kitchen sink venting, then you can just cut and cap the current horizontal trap arm, and drop the sink drain down through the plate and reconnect the sink drain there. If you do that and there's a 2" or larger drain down there, there's an advantage to making the sink drain in the wall 2", with a 2" cleanout.

Cheers, Wayne
 

wwhitney

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There are stud supports sold to brace the studs when holes are drilled.
Have you see any for quadruple 2x's?

I guess if the OP drops the horizontal trap arm enough to fit two stacked stud shoes, one could skip the sistering and just install the stud shoes on both the old and new holes. Still would probably be impossible to fill all the holes facing that narrow stud bay between the king and common stud.

Cheers, Wayne
 

PTMARC

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Thanks for the replies....I think I figured that was going to be the answer just was hoping that I missed something. I like idea of the sistering and maybe even stacking the stud shoes....but will be impossible to get proper fasteners in like you said...I may support the wall and remove the cripples and common stud while sistering the king and get triple stud shoes on before replacing cripples and common with fresh lumber. this may not look pretty but I think it should be strong enough....probably stronger than what's there currently.
 

wwhitney

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Problems of buying the sink before opening up the walls....
The sink you have is a sunk cost (so to speak), which means it's just a question of which is cheaper/less hassle, changing the DWV and framing or changing the sink.

Cheers, Wayne
 

PTMARC

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If i could get the garbage disposal drain to be one inch above the center of the current drain pipe is that going to be enough to make sure water all runs out of the disposal? or am I cutting it too close? thanks
 

Terry

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I would plumb down to the basement, and then add an AAV for the p-trap venting.
That also might allow you to bring 2" pipe up, a 2" cleanout, then the santee for the p-trap above that.

For a 10" deep sink, I figure the trap arm should be 16"above the floor.
Above the trap arm, you can 90 back out of the wall for the AAV, which should be at least 4" higher than the trap arm.

Is that a code legal way in your state? I don't know. Many places allow it though.
It would also allow you to sister some 2x4 studs alongside the others after you remove the horizontal piping. That would certainly strengthen the wall there.
 

PTMARC

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I would plumb down to the basement, and then add an AAV for the p-trap venting.
That also might allow you to bring 2" pipe up, a 2" cleanout, then the santee for the p-trap above that.

For a 10" deep sink, I figure the trap arm should be 16"above the floor.
Above the trap arm, you can 90 back out of the wall for the AAV, which should be at least 4" higher than the trap arm.

Is that a code legal way in your state? I don't know. Many places allow it though.
It would also allow you to sister some 2x4 studs alongside the others after you remove the horizontal piping. That would certainly strengthen the wall there.
Thanks Terry
Any issues using an AAV with Disposal and Dishwasher? I do like the idea of AAV and 2" drain, but feel like I "should" use vent stack to fresh air.....not sure if thats just because it was how it was done before and not necessarily any better than using an AAV.
Would you just cap off the old drain at the Tee and leave the vent attached? Not sure if that vent connects to vents upstairs so don't want to cap that off especially since could carry rain water and would need it to drain out possibly.

Virginia uses IPC which do allow AAV use, I have one in my laundry room.
 

Terry

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An AAV works fine for a kitchen sink with dishwasher and disposer.
Keep the existing vent in the wall intact going up to the next floor. You don't need the horizontal over to it. It's also too low for a revent which should be 6" above the counter height.
 
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