Sink in another room sharing drain and vent from bathroom?

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Hemi345

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Good morning,

I'm finishing my basement of my Colorado home built in 2007. The builder roughed in the drain and vent for a bathroom. I don't know what the configuration is under the basement floor slab, but we have three pipes in the floor: one horizontal pipe down in a section of the floor that was left open for shower/tub (that I'll need to add a p-trap), one for the toilet, and one that is the drain for the lav and I'm assuming will also wet vent the shower since there aren't any other pipes coming up. There is a 2" pipe coming out of the ceiling that is capped off that is the vent. Here's a drawing of the floor plan and how I think the pipes are laid out under the slab and how I want to plumb the lav and sink in the room adjacent.

20211210_100542.jpg

Our county uses IPC 2018 with the following amendment for wet venting:
pp. IPC Section 912.1 Horizontal wet vent permitted Add a new exception to read: Exception: Fixtures other than those considered to be bathroom group fixtures, of equivalent drainage fixture units, may be included in the wet vented section provided the total number of drainage fixture units does not exceed the total number included in two bathroom groups and the fixtures not considered bathroom fixtures are valued at one drainage fixture unit or less.

Can we add that sink in the other room to this?
 

wwhitney

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What type of sink is the sink in the other room?

If that sink is a lavatory, it could be considered part of the bathroom group, so you don't need that amendment, it would comply without it.

Otherwise, I don't think that amendment helps you, as all other sink types are considered more than 1 DFU:

https://up.codes/viewer/colorado/ipc-2018/chapter/7/sanitary-drainage#709.1

Although I suppose if you can find a bar sink that uses a 1-1/4" tailpiece and trap, you have a case that it is only 1 DFU per Table 709.2

Cheers, Wayne
 

Hemi345

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That sink would be in a craft/hobby room. Something stainless that's easy to clean to get water for water colors, wash out the paint brushes, grab a glass of water, etc. We were wanting to use something around the size of a bar sink, maybe a little bigger. I saw that DFU table earlier and when I saw the amendment saying only 1 DFU, that's when I figured I probably better ask. I'm not finding anything that looks like a bar sink that says it has a 1-1/4 tail piece. Most sinks look like they can accept a garbage disposal so I'm assuming 1-1/2 since they don't specifically mention it.

I guess something like this might work, but defiantly not ideal for how we'd be using it...
https://www.homedepot.com/p/Ruvati-...t-Rectangular-Bathroom-Sink-RVH6110/302944987
:(
 

wwhitney

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Seems like your choices for the utility sink are:

1) Open the slab to connect your utility sink drain downstream of the WC connection.
2) Find a utility sink that will take a 1-1/4" tailpiece (or a reasonable way to downsize) and call it 1 DFU.
3) Violate the IPC.

Cheers, Wayne
 

Hemi345

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WorthFlorida, Thanks for the link. That's pretty much what we want to put in there. I'm having trouble finding a 2" drain fitting with a 1-1/4" tailpiece though. I thought I found one... the "Elkay LK9" at https://www.prodrinkingfountains.com/elkay-lk9-commerical-sink-accessories/
but when I look it up on Elkay's site, they say it has a 1-1/2" tailpiece. I've emailed Elkay to see if they can confirm what it is.
 

Hemi345

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Seems like your choices for the utility sink are:

1) Open the slab to connect your utility sink drain downstream of the WC connection.
2) Find a utility sink that will take a 1-1/4" tailpiece (or a reasonable way to downsize) and call it 1 DFU.
3) Violate the IPC.

Cheers, Wayne
1) is a no go, we'd rather go without the sink.
2) is looking more promising. Would this work to adapt a 1-1/2" tailpiece to 1-1/4" trap?
https://www.amazon.com/Keeney-46WK-Straight-Extension-Coupling/dp/B000BO8EE4/
3) I'm having everything inspected, so probably can't do that. :)

Thank you both for your help.
 

wwhitney

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I meant to add that I can't tell if that part has the nice conical interior transition, which is why I said "maybe."

Cheers, Wayne
 

Hemi345

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I meant to add that I can't tell if that part has the nice conical interior transition, which is why I said "maybe."
Cheers, Wayne

It doesn't look like it has much of a taper from 1-1/2 to 1-1/4, but I wouldn't think it would cause any crud to collect on the transition either.

After thinking about this some more, if I'm adapting a 1-1/2" tail piece to 1-1/4" anyway, doesn't that open up the possibility to use sinks with 3-1/2" drain openings? Like this sink ( https://www.elkay.com/products/details/ectru12179t ) with the LK35 drain piece ( https://www.elkay.com/products/details/LK35 )
 

wwhitney

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I don't know. Table 709.1 specifies "sinks" as 2 DFUs without further clarification. Table 709.2 specifies that for other fixtures, 1-1/4" trap means 1 DFU. Since sinks are listed in Table 709.1 I think it's a bit of a stretch code-wise, but quite reasonable physics-wise, to say that a non-lavatory sink with a 1-1/4" trap is only 1 DFU.

So if you use a sink you can call a lavatory, I think you're on solid ground. If you use some other sink that accommodates a drain with a 1-1/4" tail piece, hopefully the inspector will be agreeable to applying Table 709.2 instead of Table 709.1. If you have to adapt down from a drain with a 1-1/2" tailpiece, I don't know if that will make the inspector less agreeable or not.

Cheers, Wayne
 
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Hemi345

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Yeah, I get what you're saying, thanks for the sanity check Wayne :D I think we'll stick with a stainless lav that accepts a 1-1/4 tailpiece. Elkay says their bar sinks or the sink WorthFlorida mentioned is made to accept the drain with 1-1/2 tailpiece. My wife found this one that looks up to the task:
https://www.homedepot.com/p/Karran-17-25-in-Bathroom-Sink-in-Stainless-Steel-UV-1816/318029771

One additional question. I was planning to plumb the drain pipe in this order from floor up...
1) 2" cleanout
2) 2 x 2 x 1-1/2" sani tee to 4.5' of 1-1/2" pipe to 1-1/2" long radius 90deg elbow to 1-1/2" x 1-1/4" hub x slip-joint trap adapter for the bathroom lav
3) 2 x 2 x 1-1/2" sani tee to 1-1/2" x 1-1/4" hub x slip-joint trap adapter for the craftroom lav
4) 2" pipe up to connect to vent

Does that order look good?
 
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wwhitney

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With a 1-1/4" trap you are limited to 1-1/4" of fall and 5' of length on the trap arm, so I would suggest it makes more sense to use a 1-1/2" trap for the bathroom lav. Otherwise you'd be cutting it close.

On the craftsroom lav, since it is close to the stack and since its status is uncertain, sticking with the 1-1/4" trap makes sense. If possible a trap adapter than has the reducing to 1-1/4" built into the slip joint nut would give you most future flexibility. [Maybe they all do, I don't know.]

Cheers, Wayne
 

Tuttles Revenge

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flanged tail pieces used for vessel sinks have a nut that threads onto 1.5" drain bodies such as a Jr Basket strainer commonly used for Bar Sinks. The flanged tail piece is 1.25" which would fit the description.

Delta pop up assembly


1.25 tail piece.jpg
 

Tuttles Revenge

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And likely if you chat with your inspector about exactly what you want to do, they will likely grant you a waiver/exemption to the code. If the sink is going to be used as described and not turned into a kitchen or laundry.
 

Hemi345

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@Tuttles Revenge What you show is elusive in all my searching. I spent a few hours trying to find such a beast last Friday. I'm probably not using the correct search terms. But good point about talking to the inspector about what we want to do when I get the rough inspection.
I was planning to just glue in a length of 1-1/2" pipe out of the tee that I'll cap (do the same in the bathroom coming out of the 90deg elbow) so I can do the pressure test. Then I'll ask the inspector about craftroom sink. Then I can cut down the pipes and put on the recommended fitting to connect the traps.

@wwhitney : So one of these then:
https://www.homedepot.com/p/Charlotte-Pipe-1-1-2-in-ABS-DWV-Trap-Adapter-ABS00104P0800HD/313834571
 

wwhitney

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