basement sink to share drain?

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rphw318

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The 1.5" pipe for the kitchen sink runs into the basement, then wye connects to a 2" pipe (with access cap) before going under the concrete slab. The kitchen sink is vented to outside. I'm interested in putting a small sink nearby, and I was wondering if it would be acceptable to connect the new sink's 1.5" to the 2" pipe shared with the upstairs sink. As for venting, could this new sink be vented with an AAV under the cabinet? Also, I'm concerned that a full sink of water from upstairs might tend to push back up into the basement sink.

Any advice would be greatly appreciated. If this is feasible, I'm likely to hire someone for this project, but am looking to understand things before starting the process.

Thanks,
Russell
 
Last edited:
It could connect there and should be fine unless the line becomes obstructed.

I'm not a fan of aav's and this application is not the best used for one.

the basement sink could see pressure which an aav cannot vent.
 
Hi Redwood,

So, if I understand you correctly, the basement sink should only see pressure if the 2" pipe becomes restricted? Is there some sort of check valve that could be put into the basement sink drain to prevent the kitchen waste from going into the basement sink?

As for the venting, is running to the pre-existing vent the only option here? If that's the case, I might need to re-think this whole thing, as the cost of running the new vent might be too high.

Thanks again,

Russell
 
rphw318 said:
So, if I understand you correctly, the basement sink should only see pressure if the 2" pipe becomes restricted?
Click to expand...

No the water falling from above may sometimes generate pressure which will make popping noises with the water in the trap of the basement sink.

rphw318 said:
Is there some sort of check valve that could be put into the basement sink drain to prevent the kitchen waste from going into the basement sink?
Click to expand...

Yes but the reliability of the basement drain will probably suffer and maintenance would be required

rphw318 said:
As for the venting, is running to the pre-existing vent the only option here? If that's the case, I might need to re-think this whole thing, as the cost of running the new vent might be too high.
Click to expand...

Consult your locally used code and ask what is allowed. The best choice is always a vent through the roof.
 
why would you worry about venting the new sink when the drain line you are tapping into is already vented?
 
Daryl in Nanoose said:
why would you worry about venting the new sink when the drain line you are tapping into is already vented?
Click to expand...

Because if there is waste coming from above it is a drain not a vent.
So therefore it is not vented.
 
But that would be only when the kitchen sink is being used at the same time right?
 
The purpose of venting is to protect the trap seal.

The water from above coming down the line from above is the very thing you are trying to protect the trap seal from.
 
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