New kitchen sink in island

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Iubkb

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Please excuse the rough drawing but we are tearing out our kitchen sink that is along the wall and moving it to a new island. The drain is in the crawlspace directly underneath the new sink in the island. Can I just cap off the old sink drain line where it enters the wall and hook a t into the drain line under the island sink and it will still drain as it is connected to the old drain and vent line?

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BobinTN

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The sink in the island will need it's own vent. The venting is on the high side of the trap arm to the p-trap, not below.

An example below

FH03OCT_ISLANSI_01.JPG
I used this same photo to do a similar vent in a friend's kitchen remodel -- there was no way to vent in and up into a wall -- it went down to a basement and I was able to vent through the exterior wall and run the vent stack on the exterior wall up two stories to vent to air.
 

Reach4

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Under IPC, you can use an AAV.

From https://terrylove.com/forums/index.php?threads/will-this-drain-aav-in-island.56853/

The AAV could be set lower than in this photo, for easier access. But this photo shows the general concept for your island.

aav-kitchen.jpg


That venting that Terry showed is top notch, but the AAV is easier and is going to be more popular where allowed. If you will have a disposal, then the trap will go lower. The cleanout can be above the trap, or if it will be accessible, you can unscrew the AAV and use the opening as a cleanout.

AAV 4 inches above the trap is sufficient.
 

BobinTN

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Under IPC, you can use an AAV.

From https://terrylove.com/forums/index.php?threads/will-this-drain-aav-in-island.56853/

The AAV could be set lower than in this photo, for easier access. But this photo shows the general concept for your island.
aav-kitchen.jpg


That venting that Terry showed is top notch, but the AAV is easier and is going to be more popular where allowed. If you will have a disposal, then the trap will go lower. The cleanout can be above the trap, or if it will be accessible, you can unscrew the AAV and use the opening as a cleanout.

AAV 4 inches above the trap is sufficient.
Not a big fan of using AAV's
 

Dielectricunion

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Modified in 2018ish, the IPC also allows combination waste/vent to be used at kitchen sink, which is even simpler but would require 2" to the trap arm.
 

Dielectricunion

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Interesting. Page 16 of https://www.iccsafe.org/wp-content/uploads/20-18927_GR_2021_Plumbing_Venting_Brochure.pdf discusses the Combination Waste and Vent System.
It was previously limited to floor drains and sinks receiving only liquid (aka no disposals, dishwasher gross food scrap shit) under the assumption that solids could impact the ability to vent but some further research showed no impact. The other requirement, if I'm remembering right, is that horizontals slope 1/2" per foot
 

Reach4

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It was previously limited to floor drains and sinks receiving only liquid (aka no disposals, dishwasher gross food scrap shit) under the assumption that solids could impact the ability to vent but some further research showed no impact. The other requirement, if I'm remembering right, is that horizontals slope 1/2" per foot
That would be a maximum:
"For this reason, the horizontal portion
must not exceed a slope of one-half
unit vertical in 12 units horizontal,
or 4-percent slope. The horizontal
length of a combination waste and
vent system shall be unlimited."
 

Jeff H Young

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Combo waste and vent? are we talking putting a floor sink in, an S-trap or a trap below floor on a kitchen sink?? weird new code you got there
If I was in IPC I'd go with an AAV or an Island vent in UPC.
 

Reach4

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Combo waste and vent? are we talking putting a floor sink in, an S-trap or a trap below floor on a kitchen sink?? weird new code you got there
If I was in IPC I'd go with an AAV or an Island vent in UPC.
We are talking about a kitchen sink, using a method originally limited to floor drains.
So the tailpiece gets increased to 2-inch, and there is a 2-inch trap under the floor.
 

Reach4

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I guess 3 foot long tailpieces is how they roll in IPC? ok if that's your code
Shocking enough, but they also do that in Canada. What is really shocking is "As long as both
the horizontal drain and vent system and the maximum 8-foot riser to a fixture drain are sized in
accordance with Table 915.2.2, the flow of free air will be sufficient for the propped design."

So the real shock is 8 ft!!!, if I read that right.
 
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Dielectricunion

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We are talking about a kitchen sink, using a method originally limited to floor drains.
So the tailpiece gets increased to 2-inch, and there is a 2-inch trap under the floor.
Does the trap have to be under the floor? I thought it could still have a typical trap arm in the cabinet before dropping to a vertical
 

wwhitney

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We are talking about a kitchen sink, using a method originally limited to floor drains.
So the tailpiece gets increased to 2-inch, and there is a 2-inch trap under the floor.
Not a trap below the floor, IPC 1002.1 still limits the "vertical distance from the fixture outlet to the trap weir" to 24" maximum. But with CW&V, IPC 915 allow a vertical pipe connecting the trap arm to the combination waste and vent to act as a vent, per 915.2.

So the geometry ends up like an S-trap, but the vertical drain is oversized. And the minimum trap arm length of 2 pipe diameters would still apply, to my understanding. I would expect often the elbow turning down would be inside the wall, just replacing the usual san-tee.


Cheers, Wayne
 

Reach4

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Then you interpret the 8 ft to apply to the combination vent/drain above the santee, or what?
 

wwhitney

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Then you interpret the 8 ft to apply to the combination vent/drain above the santee, or what?
What san-tee? The 8 ft would be the maximum allowable riser between the combination waste and vent (which all has to be horizontal at a maximum pitch of 4%) and the elevation of the trap arm. The trap arm would connect to the riser with a quarter bend.

Cheers, Wayne
 

Jeff H Young

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What san-tee? The 8 ft would be the maximum allowable riser between the combination waste and vent (which all has to be horizontal at a maximum pitch of 4%) and the elevation of the trap arm. The trap arm would connect to the riser with a quarter bend.

Cheers, Wayne
Thanks for pointing that out Wayne . A real foreighn concept to allow venting in such way and I missed that, kinda steered Dilectricunion wrong by saying trap would be under floor .
 
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