Split level home: running new kitchen sewage line in existing downstairs bathroom plumbing

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HoltH

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Remodeling a kitchen that is on the upstairs floor in a split-level home. Moving the kitchen sink to a new location (want it under the window). The new location prevents me from running the drain into the upstairs bathroom plumbing, like the old sink did. Instead, it appears my only option is to tie it in to the downstairs bathroom drain. Below is my current plan on how to connect the drain line to the downstairs bathroom:

Screenshot_20220528-211513.jpg


Because of the window directly above the sink, I am planning to use an Air Admittance Valve (AAV) for venting the sink. From the research I have done, it appears to be in code (in Ohio), but correct me if I'm wrong.
My main concern is how I should connect the kitchen sink drain to the bathroom drain. Is the above solution allowed?
I'm not sure if I can connect the kitchen drain above the bathroom sink drain, since it is using the vent. An alternative solution is below:

Screenshot_20220528-212059~2.jpg


Still using an AAV vent for the kitchen sink, and connecting the drain line below the downstairs bathroom line. This solution uses more material, because I can't run the line to the right if the downstairs vent due to lack of space.

Are either of the above solutions a good idea? I need it to pass inspections.

Here is the current drain line and vent for the downstairs bathroom that I plan to connect to:

Screenshot_20220528-212709.jpg

Any help is appreciated. Thanks!
 

John Gayewski

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You can't wet vent from the floor above. You need to tie in below the sink connection.

dwv_b2.jpg
 
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Terry

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In a true plumbing sense, the kitchen should come in downstream of the plumbing in the floor below, not use the venting for the downstairs bathroom. Even tying in below the downstairs sink, that still winds up using the toilet venting. Will it work since the toilet has a 3' vent at that point, I suppose. I would not want to be the one to run it by an inspector though. Nope, not me!
 

HoltH

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So, if I tie in below the downstairs sink connection (like in the image below) I should be good?

Screenshot_20220528-212059~2.jpg
 

Reach4

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Sometimes it is good to run the new drain lines into the yard, and to wye into the drain line in the yard. If you don't have an outside cleanout, you can add that to the project.

So sometimes the line goes around the side of the house. You can slope the line 1/8 inch per foot with the right considerations.

I am not saying that adding the new drain indoors is not good. I am just suggesting something that makes some projects easier.
 

HoltH

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Okay, so here is another option. Using this method, I would be tying in just below all of the upstairs sewage plumbing. I would still vent the sink with a AAV vent. The picture below show where I want to tie it in:
Screenshot_20220529-090247.jpg



Would this work? Everything in this image connects to a vent that goes out the roof. I would leave the old kitchen drain vent connected as well so I don't mess anything up. Any thoughts?

I can provide a clearer diagram if needed.

Again, trying to find a solution that works and passes the mechanical inspection.
 

Reach4

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I think everybody will approve of your latest markup.

Rather than a santee at the bottom of the blue, you could have a wye. Then use a 45 into the side port to receive the waste from above.
 

HoltH

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I think everybody will approve of your latest markup.

Rather than a santee at the bottom of the blue, you could have a wye. Then use a 45 into the side port to receive the waste from above.
Thanks for the input. Just want to confirm I understand what you are saying. Is this what you meant?
Screenshot_20220529-184651.jpg
 

HoltH

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Last question (hopefully): is it code to use a rubber coupling like a fernco wye to tie into the existing drain?
 

HoltH

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now your plan looks much better!I thought you were on slab
Sorry for the misunderstanding. The house is on a slab and the kitchen is on the second floor (split level). My first plan was to tie into the plumbing on the first floor right above the slab. My second (and apparently better) plan is to tie into the plumbing right below the second floor.
 
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