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Old 01-18-2008, 05:46 PM   #1
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Two drains, one trap?


Im working on finishing my basement. My bathroom vanity drain will be run in a 2X6 wall. Directly on the other side of the wall from the vanity I would like to put a kitchenette. First, can I? Second, how would I connect the two sink drains (bathroom sink, kitchenette sink) to one drain pipe?

Do I put a trap under each sink and then put a T in the wall to connect to the two after they are trapped? Or have both sinks connected first, then T down to one trap, then to the drain?

Currently, the roughed-in drain for the sink runs vertically from floor to ceiling 2 feet to the right of the vanity with a capped off T facing the direction of the bathroom vanity.


THanks.


Last edited by tigerbalm2424; 01-18-2008 at 05:49 PM.
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Old 01-19-2008, 11:28 AM   #2
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Two drains, one trap?


Caveat: I am not a professional plumber and you are getting into areas of venting which may require at least some guidance from one.
-----------

It sounds like you are trying to install back to back fixtures.

The UPC (704.2) specifies the use of a double fixture fitting for this purpose. It is a special kind of cross designed for the connection of back to back drains. A double sanitary tee used to be used for this purpose but at least as per the UPC the double fixture fitting is now required.

The remaining issues here (that I see) are that your trap arm lengths aren't too long, that the drain pipe is sized appropriately for your two fixtures and then there is the issue wet venting. Are there fixtures that use this drain pipe above it? I may be a bit confused on this point. The UPC doesn't seem to allow wet venting between floors. I'm not quite sure about the IPC.

If the fixtures are approximately back to back then trap arm length won't be an issue. If it is a two inch drain pipe then drain pipe size probably won't be an issue but this depends on what other fixtures are draining into this pipe.

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Old 01-19-2008, 05:03 PM   #3
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Two drains, one trap?


Quote:
Originally Posted by davefoc View Post
Caveat: I am not a professional plumber and you are getting into areas of venting which may require at least some guidance from one.
-----------

It sounds like you are trying to install back to back fixtures.

The UPC (704.2) specifies the use of a double fixture fitting for this purpose. It is a special kind of cross designed for the connection of back to back drains. A double sanitary tee used to be used for this purpose but at least as per the UPC the double fixture fitting is now required.

The remaining issues here (that I see) are that your trap arm lengths aren't too long, that the drain pipe is sized appropriately for your two fixtures and then there is the issue wet venting. Are there fixtures that use this drain pipe above it? I may be a bit confused on this point. The UPC doesn't seem to allow wet venting between floors. I'm not quite sure about the IPC.

If the fixtures are approximately back to back then trap arm length won't be an issue. If it is a two inch drain pipe then drain pipe size probably won't be an issue but this depends on what other fixtures are draining into this pipe.
There is one bathroom sink drain in the upstairs bathroom on this drain, the drain is 2" PVC. So there would be the one upstairs and the two downstairs (back to back) on this 2" drain, thats it. I guess I need to look into the double fixture fitting.
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Old 01-19-2008, 06:25 PM   #4
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Two drains, one trap?


To do this correctly you will need to cut the 2 inch pvc down toward the floor. Install a wye fitting toward the openings on bottom floor. If your back to back sink/kitchen is close enough you may install a cross to catch both openings. Code in our state says to than put a cleanout tee above the cross.
Then you must run a 1-1/2 pipe above this and tie it 6 inches above the spill rim of sink on next floor (this is considered your vent).
If your bottom floor sinks are not close enough to each other then a second wye will be needed to catch both drains. Then you can tie the vents on both these sinks back together and make a single vent terminate above upstairs sink.
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Old 01-19-2008, 06:52 PM   #5
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Two drains, one trap?


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To do this correctly you will need to cut the 2 inch pvc down toward the floor. Install a wye fitting toward the openings on bottom floor. If your back to back sink/kitchen is close enough you may install a cross to catch both openings. Code in our state says to than put a cleanout tee above the cross.
Then you must run a 1-1/2 pipe above this and tie it 6 inches above the spill rim of sink on next floor (this is considered your vent).
If your bottom floor sinks are not close enough to each other then a second wye will be needed to catch both drains. Then you can tie the vents on both these sinks back together and make a single vent terminate above upstairs sink.
Could you provide a diagram of this, possibly? THat would be awesome.
Sink/Kitchen drains will be within 2 feet. What is a WYE fitting? Thanks!
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Old 01-19-2008, 10:51 PM   #6
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Two drains, one trap?


Hope this helps
A wye is like a tee but the branch comes off at a 45 degree angle scan0002.jpg (7.5 KB)
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Old 01-19-2008, 11:21 PM   #7
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Two drains, one trap?


Quote:
Originally Posted by Fitter View Post
Hope this helps
A wye is like a tee but the branch comes off at a 45 degree angle scan0002.jpg (7.5 KB)

Just like the picture is how it's done under UPC.
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Old 01-20-2008, 01:36 AM   #8
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Two drains, one trap?


Fitter, that was a nice drawing. Thank you. This is an area that I have been trying to understand better and your drawing helped.

It seems like the need to prevent a wet vent almost precludes the use of a cross fitting in this situation? Is that correct?
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Old 01-20-2008, 08:57 AM   #9
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Two drains, one trap?


Ok, now I am slightly confused after looking at the drawing. Below is a pic I just snapped to show what rough-in im dealing with.

Left Pipe with the fitting currently capped off is the sink drain coming from upstairs that I want to tap into. THe sinks will be 2 feet to the left of the currently tapped off fitting. Center pipe is the toilet drain from upstairs, and the right is the vent.


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Old 01-20-2008, 09:19 AM   #10
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Two drains, one trap?


There are other ways this can be done, this is UPC code
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Old 01-20-2008, 09:37 AM   #11
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Two drains, one trap?


Quote:
Originally Posted by Fitter View Post
Hope this helps
A wye is like a tee but the branch comes off at a 45 degree angle scan0002.jpg (7.5 KB)

This work?



ok, if I understand whats going on , my venting in this diagram wont work, right. Or would this work?

Last edited by tigerbalm2424; 01-20-2008 at 09:49 AM.
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Old 01-20-2008, 09:40 AM   #12
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Two drains, one trap?


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There are other ways this can be done, this is UPC code
The one in your drawing that say NEW VENT TIE TO UPPER, where does that actually go? The vent pipe, if I understand it correctly, is the third pipe on the right on the picture.
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Old 01-20-2008, 09:49 AM   #13
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Two drains, one trap?


Is there a sink on the upper floor?

Talking UPC here, third pipe from right including what I draw in, if that is a drain from the upper floor and you try to use it for a vent on the lower floor fixture it's not allowed, you can only wet vent on the same floor level, so this means you have to add a new drain off the lower end as shown, then take the vent back to the upper floor and tie back into the existing 6" abouve the flood lever of the upper fixture.

Confused, I bet, codes can get that way.
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Old 01-20-2008, 10:27 AM   #14
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Two drains, one trap?


Tiger
if the pipe in your picture on the far right is strictly a vent (nothing upstairs drains into it) you can tie your vent from the 2 new sinks (left) into it.
It looks like the toilet waste stack (middle ) is in the way to connect it thru the wall , so if there's room above the ceiling take the new vent outside the wall, around the waste stack ,and tie back into the existing vent.
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Old 01-20-2008, 10:28 AM   #15
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Two drains, one trap?


Quote:
Originally Posted by Ron The Plumber View Post
Is there a sink on the upper floor?

Talking UPC here, third pipe from right including what I draw in, if that is a drain from the upper floor and you try to use it for a vent on the lower floor fixture it's not allowed, you can only wet vent on the same floor level, so this means you have to add a new drain off the lower end as shown, then take the vent back to the upper floor and tie back into the existing 6" abouve the flood lever of the upper fixture.

Confused, I bet, codes can get that way.
First, I want to say thanks for the continued help with this!

Ok, so lets do it this way. Here is a diagram of what I can see for the plumbing in this area of the house. The upstairs is finished so I cant see whats in the wall. I went outside and the only vent stack coming through the roof in this area looks to be 3" or 4" diameter.

All I need to do to finish the bathroom is figure out the sink drain. If I understand Ron correctly, this red would be what I would need to do to add a back to back sink(correct me if I am wrong). Is there any way to do the back to back sink without needing to tie back in above the upstairs sink drain?

Thanks again guys!


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