Sink in another room sharing drain and vent from bathroom?

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Hemi345

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The drawing below is what I am planning to do:

20211215_170621.jpg



But then I saw this thread with the following photo. Is this because that person's pipe is 1-1/2 for drain and vent so the lav on the left needed a separate path for the vent?

index.php


I don't think I need this because the distance between the bath lav and the stack is only about 4 ft and the stack is 2" diameter, correct? Or was the revent added so the trap connections can be at the same height due to having two tees stacked on top of each other?
 
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Hemi345

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Any input on if a revent is necessary or more beneficial for my setup or should it be good as I have drawn it?
 

wwhitney

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If your bath lav trap arm length is within the limits (including the portion outside the wall), your drawing is fine. Main reason to choose one over the other is to get the lav/sink drain stub out heights you want. Or if you're opposed to wet venting one sink from the other. [Obviously you'll be wet venting the downstream WC either way.]

Cheers, Wayne
 

Hemi345

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Yes, it should be. IPC 2018 says 1-1/2" max distance is 6ft from vent to trap. The length of the arm including in the wall and coming out to the trap adapter would be right at 4ft. So using 1/4" of slope on the trap arm, the trap weir will be 1" higher than where it tees off the stack. Since the distance center to center of the two tees is 4-1/2", that'll make the bathroom trap adapter 3" lower than the one in the craft room.

What height do you all normally rough these in at? I've seen heights between 16-21" but cannot find anything in the IRC or IPC so I was thinking 17" to match a few of the existing bathrooms in my home. But that would mean the bathroom height will be 14" if the craftroom height is set to 17". Is 14" too low? If so, should I raise the two tees so the craftroom lav is a little higher to get the bathroom height >16" ? If not, is it acceptable to use a 90deg elbow to get the height a little higher, like in my photo below?

upload_2021-12-16_17-25-38.jpeg
 

Hemi345

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Oh right, because that would siphon the P, thanks Terry. So I'd need to revent that trap arm if I want the trap adapter to sit at the same height as the one in the craftroom.
 

wwhitney

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More specifically, the drop on a 1-1/2" trap arm from the trap to the vent connection can be at most 1-1/2".

You could put the craft sink lower than normal, with the lav just a little above normal (make sure you don't get it too high, ideally by having all the finished plumbing on hand and checking). That would accommodate any future change of the craft sink from a lavatory to a deeper sink. The only downside is a taller tailpiece under the craft sink, reducing storage, perhaps.

You can save a bit of height by making the upper san-tee a street san-tee.

Cheers, Wayne
 

Hemi345

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More specifically, the drop on a 1-1/2" trap arm from the trap to the vent connection can be at most 1-1/2".

You could put the craft sink lower than normal, with the lav just a little above normal (make sure you don't get it too high, ideally by having all the finished plumbing on hand and checking). That would accommodate any future change of the craft sink from a lavatory to a deeper sink. The only downside is a taller tailpiece under the craft sink, reducing storage, perhaps.
That's a good idea of putting the craftroom tee below the tee for the bathroom lav and making one slightly higher and the other slightly lower. That should work well.

You can save a bit of height by making the upper san-tee a street san-tee.

Cheers, Wayne

Yeah, I tried to find 2 x 2 x 1-1/2 street sani-tee at a couple big box stores. They offered a 2 x 2 x 2 street sani tee at HD. Thanks again Wayne.
 

wwhitney

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Yeah, I tried to find 2 x 2 x 1-1/2 street sani-tee at a couple big box stores. They offered a 2 x 2 x 2 street sani tee at HD. Thanks again Wayne.
If that's all you can find, you can put a 2 x 1-1/2 bushing in that.

Cheers, Wayne
 
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