# Two drains, one trap?



## davefoc (Dec 18, 2007)

Caveat: I am not a professional plumber and you are getting into areas of venting which may require at least some guidance from one.
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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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## tigerbalm2424 (Feb 28, 2007)

davefoc said:


> 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.
> ...


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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## Fitter (Jan 20, 2008)

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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## tigerbalm2424 (Feb 28, 2007)

Fitter said:


> 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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## Fitter (Jan 20, 2008)

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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## Ron The Plumber (Jun 7, 2006)

Fitter said:


> Hope this helps
> A wye is like a tee but the branch comes off at a 45 degree angle
> 
> 
> ...



Just like the picture is how it's done under UPC.


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## davefoc (Dec 18, 2007)

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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## tigerbalm2424 (Feb 28, 2007)

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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## Ron The Plumber (Jun 7, 2006)

There are other ways this can be done, this is UPC code


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## tigerbalm2424 (Feb 28, 2007)

Fitter said:


> Hope this helps
> A wye is like a tee but the branch comes off at a 45 degree angle
> 
> 
> ...


 
This work?










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


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## tigerbalm2424 (Feb 28, 2007)

Ron The Plumber said:


> 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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## Ron The Plumber (Jun 7, 2006)

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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## Fitter (Jan 20, 2008)

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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## tigerbalm2424 (Feb 28, 2007)

Ron The Plumber said:


> 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!:thumbsup: 

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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## Ron The Plumber (Jun 7, 2006)

tigerbalm2424 said:


> This work?
> 
> 
> 
> ...


Did not see this one you made, this will be fine providing there is no sink on the line coming from the upper floor.


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## Ron The Plumber (Jun 7, 2006)

tigerbalm2424 said:


> First, I want to say thanks for the continued help with this!:thumbsup:
> 
> 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.
> 
> ...



Works for me, I'd rather see you replace that lower tee with a wye, will make it easier to clean the line out if needed, a tee can cause a sanke to gp up even you you don't want it to, wye will make it go in the direction intended.


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## Fitter (Jan 20, 2008)

It looks like the pipe on the right is the vent for the lower tub/shower . If it is you could tie your new vent back into it above the bathroom ceiling (space permitting), then you wouldn't have to mess with the upstairs bathroom.


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## Ron The Plumber (Jun 7, 2006)

Fitter said:


> It looks like the pipe on the right is the vent for the lower tub/shower . If it is you could tie your new vent back into it above the bathroom ceiling (space permitting), then you wouldn't have to mess with the upstairs bathroom.


Yes you could do that if there is room inside the will past the toilet stack, or ceiling if there is room.


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## tigerbalm2424 (Feb 28, 2007)

Ron The Plumber said:


> Yes you could do that if there is room inside the will past the toilet stack, or ceiling if there is room.


So, like this?


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## Ron The Plumber (Jun 7, 2006)

Works for me


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## tigerbalm2424 (Feb 28, 2007)

Ron The Plumber said:


> Works for me


Thanks both of you guys!!:yes: Time for a HD run!


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