# How to vent a floor sink when the nearest wall is ~10' away?



## Michael.L

I'm laying out the floor plan for a small cafe. There will be a coffee bar at the service counter with a 3-compartment sink. The 3-comp sink's drain will be indirectly plumbed to a floor sink below with a required air gap. But the closest wall is 9.6 feet from the location of this floor sink. Is it acceptable for the vent to be that far from the floor sink trap? Do I just upsize the fixture arm drain pipe to ensure that the vent connection opening remains above the trap weir?


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## Keystone

Why not use an Auto Air Vent?


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## Sifu

Combination waste and vent.


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## mtlogcabin

If the 3 compartment sink is also being used as a food prep sink then it should be going to a grease interceptor 

3 " drain will allow 12 feet from the trap to the vent


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## Michael.L

mtlogcabin said:


> If the 3 compartment sink is also being used as a food prep sink then it should be going to a grease interceptor


It's not a food prep sink, but it will be used to wash out milk steaming jugs and blender jars. It *will* be drained to our grease interceptor.



mtlogcabin said:


> 3 " drain will allow 12 feet from the trap to the vent


Are you sure? According to this graphic, a 3" drain will only allow a max trap arm length of 6 feet, and that I'd need a 4" or larger to get the max trap arm length to 10 feet.


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## Michael.L

Keystone said:


> Why not use an Auto Air Vent?


One reason is that they tend to make a noise like a "whoopie cushion." Not exactly what you want customers to hear at your cafe's service bar.


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## Michael.L

Sifu said:


> Combination waste and vent.


Like this?





I don't know if the existing sewer line under the slab is deep enough to allow this type of configuration.


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## Keystone

Michael.L said:


> One reason is that they tend to make a noise like a "whoopie cushion." Not exactly what you want customers to hear at your cafe's service bar.



I can understand that. 

mtlogcabin is spot on, if your using local jurisdiction uses IPC then you will be okay.  Chapter 9, Venting from the IPC allows up to 12ft when using 3" drain at 1/8" slope.


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## Pcinspector1

2012 IPC TABLE 909.1


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## Michael.L

Pcinspector1 said:


> 2012 IPC TABLE 909.1


Thank you for the code reference. That's always better than random images culled from the interwebs. 

My apologies to Mtlogcabin for doubting you!


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## ADAguy

What you show is an island vent, commonly used on residential kitchens.


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## Michael.L

ADAguy said:


> What you show is an island vent, commonly used on residential kitchens.


Our service bar will essentially be an island. I'm curious: why plumbers would install an island vent like that rather than just upsizing the trap arm pipe to 3" (or 4")?


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## mtlogcabin

Michael.L said:


> My apologies to Mtlogcabin for doubting you!


My apologies for not including the code reference table


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## HForester

Keystone said:


> Why not use an Auto Air Vent?



AAV = Air Admittance Valve


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## James Davis

HForester said:


> AAV = Air Admittance Valve


the majority of inspectors don`t like/allow AAV`s


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## mtlogcabin

James Davis said:


> the majority of inspectors don`t like/allow AAV`s



The UPC does not allow the use of an AAV. However they can be permitted under alternate materials and methods which we have done on a case by case decision for existing buildings

 The IPC does allow them so unless the AHJ amended that section of the IPC to not allow them then inspector is not following the code and acting upon his personal wants and desires


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## RJJ

MT is correct on both accounts. The IPC does allow AAV, but you have to have access. The 3" drain should work just fine, if you want to be on the safe side go to 4" and you will have plenty of air.


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## Keystone

I'm not a fan of upsizing that small of a  fixture count due to less pipe wash, leaving a greater potential for dried particle build up within the pipe.


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## mark handler

AAVs are not included in the UPC or the CA Plumbing Code But does not prohibit the use. 
Just because they are not included does not mean they are prohibited.

CA allows the AHJ, to use discretion, on a case by case basis. This however, does not extend to commercial use.


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## ICE

Air admittance valves let air in but do not let air out.  A plumbed vent will prevent air pressure from pushing the water out of the trap.  Now I don't know if that is reason enough to ban them but I get the feeling that my jurisdiction is less than impressed.

As an aside, I don't know but I've been told that they do fail.....there was a mold buildup....some colorful stuff of the genus IMUS (It'll Make Us Sick).
I wonder what became of Don.


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## HForester

GEEZ. Commercial kitchens with floor sinks have been connected to combination waste and vent systems for decades.  You are making this toooo complicated. A single sink can be on a CWV system. The horizontal pipe of a  CWV is unlimited in length.


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## Rick18071

Doesn't the manufacture directions for the AAV override the UPC?


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## Bill Ernst

We have a drinking fountain in CA that we were supposed to run a loop vent for and forgot/overlooked. The 1.5” drain line cannot be vented conventionally because of a window directly above it’s structural steel building posts on either side. We submitted an RFI (Request For Information) asking for an AAV to be plumbed above the flood plane with an access panel (We’ll see if the architect interprets the “Not for commercial use” in this application).
Saw cutting concrete is sometimes more preferable than a discussion and hen party with the brass...
As a side note, ICE / Sawhorse (because I like your smart-ass frank responses in the few forum threads I’ve read here), how often have you checked for these while inspecting plumbing:
1. Weir of trap to vent wye distances?
2. Vent wye roll to 45 degree offset from waste line?
3. And trap weirs being below the centerline of vertical san-tee inlet?
I can only recall one inspector with knowledge of these items in 20 years ...


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## ICE

Bill Ernst said:


> As a side note, ICE / Sawhorse (because I like your smart-ass frank responses in the few forum threads I’ve read here), how often have you checked for these while inspecting plumbing:
> 1. Weir of trap to vent wye distances?
> 2. Vent wye roll to 45 degree offset from waste line?
> 3. And trap weirs being below the centerline of vertical san-tee inlet?
> I can only recall one inspector with knowledge of these items in 20 years ...


If you convert those strange terms into English I'll try to answer the question.


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## Bill Ernst

Well, the most difficult thing about learning to plumb to code is plumbing drain, waste and vent to code. I just have never encountered an inspector who understood how to inspect the items above; distances before and after trap seal (weir), etc. 
I didn’t have a question, really. Just wondered if you looked for vent fittings as they were plumbed in relation to flood plain of fixture served


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## HForester

The flood level rim of a fixture has nothing to do with the elevation of a trap weir nor where the trap weir is located with reference to the fitting that provides the vent for the trap. In UPC land, they do allow horizontal dry vent piping below the flood level rim of the the fixture. (IPC doesn't allow that.) In those situations, the connection of the dry vent piping to the fixture drain must be through the branch of a fitting where the branch is rolled up 45 degrees (or more) from horizontal. Typically, the branch fitting is a wye with a street 1/8 bend in the wye branch  such that the axis of the inlet of the 1/8 bend is horizontal (with about the same slope as the run of the wye fitting.) This made-up combination fitting is frequently called an "upright wye and 1/8 bend"  (Someone correct me if I don't have this terminology exactly right.)  I have seen this (horizontal dry vent below the flood level rim)  accomplished using a sanitary tee ("on its back") although some don't consider use of a san tee on its back as a proper drainage fitting. Many WCs in UPC land have been vented this way...For a WC, the trap is above the floor and therefore, the trap is above the dry vent. A DF has its trap above the floor....,

To me, a drinking fountain is such a benign application such the there isn't enough flow to ever cause the trap to self-siphon, If there are other vented fixtures connecting to the same horizontal branch drainage piping that the DF drainage pipe connects to (and usually a UPC system is "over vented"), the chances of a positive pressure event affecting that trap will be nil. So, why do you really need the vent for that trap? Does a loop vent really do anything to abate a positive pressure event? 

OK, there are the purists..."gotta have a code legal vent.." So, hack the floor up to you get to a point where you can bring the dry vent pipe (a horizontal dry vent pipe below the flood level rim of the fixture) up in a wall and eventually connect it to the vent system. I don't think the UPC has a length limit for a horizontal dry vent pipe below the flood level rim of the fixture other than, "the closest place to enable turning up vertically." (Again, you UPCers correct me if I am wrong on this.) I also think that the UPC allows dry vents to be FLAT (no slope) so that shouldn't cause a long run of dry vent to eventually "rise up out of the floor."


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## Bill Ernst

Ok, I didn’t ask a weir flood rim question. You misunderstood. Vertically, a vent servicing a trap cannot conform to code with a combination wye and 1/8 bend due to the weir being above the vent wye... 
All this other stuff is - I guess you just pontificating?


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## georgia plans exam

May I pontificate? 2012 I.P.C.
1. 909.1.
2. 905.3
3. 909.2     GPE


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## HForester

Bill Ernst said:


> Ok, I didn’t ask a weir flood rim question. You misunderstood. Vertically, a vent servicing a trap cannot conform to code with a combination wye and 1/8 bend due to the weir being above the vent wye...
> 
> All this other stuff is - I guess you just pontificating?




You are right….I went off the rails and didn’t understand the question.  In reflection, I think what your question/issue is about is whether you can have a horizontal dry vent pipe below the flood level rim of a fixture.


Someone else was correct: IPC Section 909.2 (the last part of the sentence) prohibits a horizontal dry vent pipe for a fixture trap located below the flood level rim of a fixture. However, because you stated "We have a drinking fountain in *CA*... " you are not working under the IPC.  Under the UPC, Section 1002.4 (a 2015 edition reference) says essentially the same thing as the IPC however, the UPC (Section 905.3) also begins the section with  "Unless prohibited by structural conditions...." This appears to allow for horizontal vent piping below the flood level rim of a fixture. Indeed, looking into the 2009 UPC Illustrated Training Manual (sorry I don't have a 2015 edition) under Section 905.3, it states in the second paragraph: 


"The vent connection is always below the overflow rim of the fixture but normally there is only a short vertical piece that is below the fixture rim: however, this is not always possible. There will sometimes be obstructions in the structure of the building that will prevent this ideal condition.  Significant portions of the vent may have to be installed below the flood-level rim of the fixture. For example, there may be an installation of a floor drain where the distance exceeds the trap to weir distance. In this installation, the vent would have to be placed in a horizontal position until it could turn vertical in the wall (see Figure 9-15)"


Figure 9-15 is a photograph showing a vent running (maybe 20 _feet_) horizontally below the slab where there will be a floor drain.  In other words, under the UPC,_ apparently,_ if it is not possible to run the vent vertically above the flood level rim of a fixture before offsetting horizontally, it is OK to run horizontally below the flood level rim. 


Now I don't agree with that practice and the UPC doesn't seem to agree with that practice (UPC Sections 1002.4 and 905.5), the "Unless prohibited by structural conditions...." of 905.3 seems to allow for horizontal dry vent piping below the flood-level rim of a fixture.  

This might help you design a solution for the venting the drinking fountain.


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## north star

*$ ~ $*

HForester,

Is it possible for you provide some images of your
explanation of Post # 29 ?..........Thanks !

*$ ~ $*


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## HForester

Can anybody else put up that UPC Training Manual Figure (Figure 9-15) ?  I can't do so for another week.


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## HForester

I added the Yellow arrow to point out that this is the dry vent pipe that will obviously be below the flood level rim of the floor drain(?) in the foreground of the figure (photo).

IMAGE available for up to 14 days from Oct 30, 2018


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