# Need Help Plumbing A Utility Sink...



## drummereef (Jan 22, 2008)

Looking to install a utility sink in an unfinished area of our basement. I'd like to install the sink between the clothes dryer and the master bath shower/toilet drain. All existing plumbing is PVC. 

My question is... Where would be the best place for the sink to drain and vent? Is it against code to plumb the drain into the washing machine standpipe? Any advice would be great. 

Thanks!

Pic of washing machine standpipe, sink placement, and master bath shower/toilet drain.











Pic of traps from the master bath drain.











Pic of master bath shower/toilet drain (left) and master bath sink drain (right)











Pic of washer/dryer, standpipe drain, and sump pit.


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## Termite (Apr 13, 2008)

I'd just tap into that 3" stack to the right for the drain. It would not be hard to cut in a wye fitting above the floor. As long as the 1-1/2" trap is no more than 6' from the stack, you can probably get away with wet venting it. 

Alteration of the washer drain pipe would be a no-no!

If you get it all piped and determine that it isn't draining/venting as well as it could be, an air admittance vent on a vertical run of pipe could easily be cut in and secured to the wall.


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## Tommy Plumb (Oct 7, 2006)

You certainly can cut the waste into the 3" stack. It wouldn't pass an inspection but you can probably get away without venting it. An AAV would probably be the best way. Is their a vent down there that you could pick up though?


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## mstplumber (May 3, 2008)

It is against code to connect to the washing machine standpipe, but it will work fine if you use a wye on the standpipe. You would not need to vent it at all if you use the standpipe.

If you want to meet code here's how:

Cut a 4 x 2 sanitary tee into the waste stack about 1' above the floor, run a 2" horizontal line to the laundry sink ( you can use 1 1/2" but laundry sinks catch a lot of crud so I like 2"), install a 2 x 1 1/2 sanitary tee on it's back and put an AAV in top or a short pipe from the tee, and last if all install a 2 x 1/12 bushing and 1 1/2 p-trap for the laundry sink. Make sure the pipe has 1/4" per foot slope and you will be both legal and functional. 

The sanitary tee on it's back is a possible source of contention with some inspectors but, since there is no flow through the branch, I think it's legal and I know it works.


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## drummereef (Jan 22, 2008)

mstplumber said:


> It is against code to connect to the washing machine standpipe, but it will work fine if you use a wye on the standpipe. You would not need to vent it at all if you use the standpipe.
> 
> If you want to meet code here's how:
> 
> ...


Wow, that's a lot to swallow... :laughing: Is there any way to mock up a drawing of this for me? You are saying to cut into the standpipe from the master bath, correct?


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## Termite (Apr 13, 2008)

drummereef said:


> Wow, that's a lot to swallow... :laughing: Is there any way to mock up a drawing of this for me? You are saying to cut into the standpipe from the master bath, correct?


That's what he means all right. It will be stinky but easy enough to do. Start by taking a look at a 4x2 wye fitting. I think it will start to make sense when you see that fitting. :thumbsup:


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## Termite (Apr 13, 2008)

mstplumber said:


> .
> The sanitary tee on it's back is a possible source of contention with some inspectors but, since there is no flow through the branch, I think it's legal and I know it works.


I'm not seeing how the sanitary tee would be on its back in this installation. It would be oriented vertically. Or am I missing something here???


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## drummereef (Jan 22, 2008)

thekctermite said:


> That's what he means all right. It will be stinky but easy enough to do. Start by taking a look at a 4x2 wye fitting. I think it will start to make sense when you see that fitting. :thumbsup:


So it's kind of like this picture, but instead of the 90 elbow on the right, that's where I would use the 4x2 sanitary tee into the main standpipe?


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## mstplumber (May 3, 2008)

Exactly. Except that looks like all 1 1/2" pipe, but the configuration is the same. 

KC-The sanitary tee to the AAV is technically "on it's back", which is not allowed in the drainage system. Since the branch of the tee receives no flow, I consider it part of the vent system, but the ICC code is not clear on this. I've had some inspectors agree with me and others not.


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## Termite (Apr 13, 2008)

mstplumber said:


> KC-The sanitary tee to the AAV is technically "on it's back", which is not allowed in the drainage system. Since the branch of the tee receives no flow, I consider it part of the vent system, but the ICC code is not clear on this. I've had some inspectors agree with me and others not.


Gotcha. I was picturing the 4x2 into the stack and wasn't thinking about connecting the AAV for some reason. If the branch of the tee were carrying waste, I'd call it, but it is silly to make an issue of it on something that is strictly serving a vent. Thanks for clarifying, since I didn't correctly read your post!


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## drummereef (Jan 22, 2008)

mstplumber said:


> Exactly. Except that looks like all 1 1/2" pipe, but the configuration is the same.
> 
> KC-The sanitary tee to the AAV is technically "on it's back", which is not allowed in the drainage system. Since the branch of the tee receives no flow, I consider it part of the vent system, but the ICC code is not clear on this. I've had some inspectors agree with me and others not.


Ok, great. Doest the AAV need to be within a certain height to the sink to avoid violation? Can it be 'hidden' underneath right at the p-trap?


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## mstplumber (May 3, 2008)

It needs to be at least 4" above the trap so it should fit under the sink.


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## drummereef (Jan 22, 2008)

mstplumber said:


> It needs to be at least 4" above the trap so it should fit under the sink.


Well, I got some more information.... I called around to some local plumbers and depending on the municipality I live in, it might be code to simply tee into the washer drain riser (as long as the overall height is maintained). I'm going to call the local gov and make sure I can do this. Thanks for the help, everyone! :thumbsup:


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## Termite (Apr 13, 2008)

drummereef said:


> Well, I got some more information.... I called around to some local plumbers and depending on the municipality I live in, it might be code to simply tee into the washer drain riser (as long as the overall height is maintained). I'm going to call the local gov and make sure I can do this. Thanks for the help, everyone! :thumbsup:


Baaaaaaad idea. But good luck. :no:


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## drummereef (Jan 22, 2008)

thekctermite said:


> Baaaaaaad idea. But good luck. :no:


:laughing: I just spoke with the chief plumbing inspector for my municipality. He said I can sanitary tee into the washer riser, as long as the original height of the riser is kept. The sink drain must also be within 30" of the riser. 

Why do you think this would this be a bad idea?


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## mstplumber (May 3, 2008)

I think it will work fine. Just remember, you don't need a trap on the laundry sink, the washer standpipe should already be trapped under the floor. If not, you would have smelled sewer gas by now.


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## drummereef (Jan 22, 2008)

mstplumber said:


> I think it will work fine. Just remember, you don't need a trap on the laundry sink, the washer standpipe should already be trapped under the floor. If not, you would have smelled sewer gas by now.


Ok, great. Yeah, I can see water at the bottom of the washer standpipe so I'm assuming it has a trap already. 

By adding an additional trap to the sink, would it potentially be a violation? Is there such think as double trapping?


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## mstplumber (May 3, 2008)

It's against code for anything to be double trapped and it serves no purpose to do so. There purpose of a trap is to prevent sewer gas from escaping the system and you already have one. Adding another one just creates more joints to leak and wastes money. Just use a trap adapter and tailpiece to connect to an 1 1/2" drain pipe.


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