Kitchen sink/disposer DWV with two san-T's

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Earl

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Hi - I don't know if this should appear here or in 'Plumbing Code Question' forum so let me know.

I'm doing a kitchen remodel and am planning the DWV plan. The standard appears to be to use one san-T in a vertical vent drain configuration and one p-trap connected to the two basins and disposer. This is what the old sink location had and I've seen plenty of on these forums.

For the new location I was thinking of using two san-T's, one right above the other, say at 13" and 16". This would allow a seperate p-trap for one basin and another for the disposer and second basin. Is this allowed? I did an extensive search here and on the internet and didn't find much. Although it is possible to use a double TY and spread the to drains horizontally (which I did see posted here by Terry) there really isn't room for this and I'd just as well revert to one san-T. It just seems have each sink with it's own trap would be more reliable and easier (after the rough-in is done).


A secondary question as well: I've been searching for the code requirements regarding the kitchen DWV pipe size. Is 2" required? This is somewhat OBE since I think I'll use 2"" anyway to be safe - but it would be good to know. What about a 2" drain and then necking down to 1 1/2" about 6" above the fixture flood line?

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I had trouble logging into my old handle (Earl001). I didn't know where the password reset was sent to so I had to create a new account.
 

Kiton

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P.S.
I had trouble logging into my old handle (Earl001). I didn't know where the password reset was sent to so I had to create a new account.

Hi Earl,
it is in a soft blue font just below the password box.
 

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Asktom

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I would just use one trap. A one trap set-up works fine and, technically, under the UPC, if you stacked san tees then the bottom trap would have an undersized wet vent in violation of code. Would it work? Sure, but why reinvent the wheel using a code infraction?
 

Earl

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I would just use one trap. A one trap set-up works fine and, technically, under the UPC, if you stacked san tees then the bottom trap would have an undersized wet vent in violation of code. Would it work? Sure, but why reinvent the wheel using a code infraction?

This is what I was wondering about and perhaps the reason I only saw the configuration only once in all the web searching I did (see attached from carnationconstruction). However, to follow up. If the wet vent is 2", as I plan, and the trap is only the standard 1 1/2" shouldn't the wet vent be large enough? In practical terms one would think the code would recgonize that the two san-T's are servicing the same water source so flow is limited. Just curious to understand the logic behind the code. Usually there are good reasons behind every requirement.

HJ - Glad you mentioned that as I was wondering about it. I should have mentioned that I am piping with an arrangement similar to the attached island plan. Does that change the thought to go to 1 1/2" above the top tee? 1 1/2" is a lot easier and one would think that would supply plenty enough venting for one kitchen faucet. But, I've learned to listen to the wisdom of this forum... and I try to be conservative in my implementation.

One thing I was wondering about in the attached sketch was the rational for using of the long TY and "long turn" on the bottom vent branch. Any thoughts on why? I was going to use a standard T fitting since it is for venting purposes. I also was not planning on a cleanout on the wall vent since that would be behind cabinetry. I did plan on adding a cleanout instead of a 'long turn' where the dran merges to the main drain at the bottom.

Kiton - I did try that. What I meant is that I was unable to access the sent email with the new password. I think it was sent to an account I don't have any more.
 

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Asktom

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The wet vent is the short section between the two san tees. A sink uses a 1 1/2" trap and arm but requires a 2" drain. That short section needs to be one pipe size larger (UPC 908.2).
 

Earl

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So, if I understand this correctly I'd have to transistion to a 3" between the two san-T's? ... That is, have my (now) 1 1/2" vent line transition to a 2" san-T, then transition to the 3" section, then transition back to a 2" san-T, and finally follow through with 2" piping to the main line later in the run??

This touches on my earier question about a kitchen 2" DWV requirement. I gathered from hj that ist's not required but recommended. Lets assume I went with 1 1/2" san-Ts. Then would it be within code to have a 1 1/2" vent connected to a 1 1/2 san-T, then transition to 2" and another 1 1/2" (or perhaps going with a 2") san-T and rout the rest in 2" to the main line?

Now I'm really curious as to others ideas on how to do this within code. Has it been done with inspector approval? Certainly I wouldn't be able to fit the 3" line very well in my 2x4 framing.
 

Asktom

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Nope, you cant jump up to 3" then drop back down. You would need to use a 2 X 1 1/2 X 1 1/2 X 1 1/2 double fixture tee then 90 out of the wall in two places at the same level.
 

Earl

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This is what Terry showed in one of the plans on this site (don't recall where). So your saying a vertical orientation can not work? I though that was the whole idea of the wet vent with 'one pipe size larger'!
Sorry - I'm confused.
 

Earl

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Come to think of it, in a kitchen scenario if each basin is attached via p-trap into a two vertical san-T configuration, one could argue that this isn't a wet vent scenario. That is becasue both basens are serviced by one faucet. Practically speaking, only one or the other san-T is in use at a time. However, I don't know if the UPC can recgonize this.

In any case, I'd really like to know if there are any real-life implementations or thoughts out there to get a two vertical san-T configuration within code.
 

Kiton

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On second reading I got that, sorry.



Kiton - I did try that. What I meant is that I was unable to access the sent email with the new password. I think it was sent to an account I don't have any more.
 

Asktom

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If you want to use two san tees and you want to meet UPC requirements you would need to put a wye down low then put a street 45 in the branch looking up. Use 2 x 1 1/2 x 1 1/2 san tees on both the branch and the barrel and run two 1 1/2 vents up until they are at least 6" above the countertop. At that point the vents can be hooked together and run through the roof.

Your set-up stacking san tees would be approved for to lavatories which only require a 1 1/2" drain but not for sinks because they need a 2" drain. The section between the two san tees (vertical wet vent) is required to be one pipe size larger than the minimum drain size for the upper fixture. For a lav one size largers is 2" but for a sink it is 3" (technically 2 1/2 - but there are no drainage fittings) and you aren't allowed to reduce the drain size so it would need to be 3" all the way to the main.
 
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