# Backflow preventer instead of air gap



## Rider Rick (Mar 9, 2010)

[attachment]3-8-2010 001.jpg1.jpg[/attachment]New restaurant with food prep sink drain to backflow preventer to grease trap to floor sink.I think the sink needs an air gap between the sink and pee-trap.Whats your take?Thank you,Rick

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## Mule (Mar 9, 2010)

Re: Backflow preventer instead of air gap

1002.1 Fixture traps. Each plumbing fixture shall be separately

trapped by a water-seal trap, except as otherwise permitted

by this code. The vertical distance from the fixture outlet to

the trap weir shall not exceed 24 inches (610 mm) and the horizontal

distance shall not exceed 30 inches (610 mm) measured

from the centerline of the fixture outlet to the centerline of the

inlet of the trap. The height of a clotheswasher standpipe above

a trap shall conform to Section 802.4. *A fixture shall not be*

*double trapped.*

Exceptions:

A *grease trap *intended to serve as a fixture trap in

accordance with the manufacturer’s installation

instructions *shall be permitted to serve as the trap *for a

single fixture or a combination sink of not more than

three compartments where the vertical distance from

the fixture outlet to the inlet of the interceptor does not

exceed 30 inches (762 mm) and the developed length

of the waste pipe from the most upstream fixture outlet

to the inlet of the interceptor does not exceed 60

inches (1524 mm).

I've never seen a set up like this.

I guess you could consider this setup as being double trapped??

Why do they have a backflow preventer on there anyway?

What does the specs say about the installation?


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## Mac (Mar 9, 2010)

Re: Backflow preventer instead of air gap

Funny - I'm more used to seeing backflow prevention on the supply side than drainage...


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## skipharper (Mar 9, 2010)

Re: Backflow preventer instead of air gap

No     If using the IPC:

1) that is a backwater valve

2) IPC is very clear on this:802.1.1 Food handling.

Equipment and fixtures utilized for the storage, preparation and handling of food shall discharge through an indirect waste pipe by means of an air gap.

Rip it out and do it right!!!


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## pwood (Mar 9, 2010)

Re: Backflow preventer instead of air gap

I believe that is a flow control device and i don't think the trap is necessary here!


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## skipharper (Mar 9, 2010)

Re: Backflow preventer instead of air gap

Regardless of what it is, this does not come close to complying, again, see 802.1.1 if using the IPC


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## MarkRandall (Mar 9, 2010)

Re: Backflow preventer instead of air gap



			
				skipharper said:
			
		

> 2) IPC is very clear on this:802.1.1 Food handling.Equipment and fixtures utilized for the storage, preparation and handling of food shall discharge through an indirect waste pipe by means of an air gap.
> 
> Rip it out and do it right!!!


Although I'm not qualified to answer this:

Skipharper, there is an air gap at the floor sink. Wouldn't that count?

I've only done a couple commercial kitchens in my career, but my memory is that we always had the air gap at the floor sink. Is not that the intention?


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## skipharper (Mar 9, 2010)

Re: Backflow preventer instead of air gap

No sir, the language of the code states:

802.1.1 Food handling.

Equipment and fixtures utilized for the storage, preparation and handling of food shall discharge through an indirect waste pipe by means of an air gap.

AIR GAP (Drainage System). The unobstructed vertical distance through the free atmosphere between the outlet of the waste pipe and the flood level rim of the receptacle into which the waste pipe is discharging.

Think about this. If the pipe over the floor sink is from the discharge side of the grease trap, what about odors in the kitchen from that outlet. If you get the cut sheet on that (or any) grease trap, it will mandate a direct connection to the sanitary from the discharge of the grease trap.


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## texasbo (Mar 9, 2010)

Re: Backflow preventer instead of air gap

Skip is absolutely right, and this is potentially a very serious health hazard. The tailpiece from the 3C sink needs an air gap. Without it, food being prepped in the sink could very easily be contaminated from waste in the drainage system. Should be corrected ASAP.


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## MarkRandall (Mar 9, 2010)

Re: Backflow preventer instead of air gap

Well, I was correct on one thing. I'm certainly not qualified in this area. What you say makes perfect sense. Thanks for giving me a little knowledge today.

Now that you explain it, I'm not sure (probably not) I've had a floor sink at a grease trap. The floor sinks I can remember were at a prep sink and dishwasher area.


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## Dr. J (Mar 9, 2010)

Re: Backflow preventer instead of air gap

pwood is correct about the grey thingy being a flow control fitting.

This arrangement is the result of incompatible requirements (the white p-trap is a result of incompetence).  Section 802.1 requires an indirect waste.  As pointed out above, the waste from the sink needs to be a straight shot from the sink outlet to an indirect waste receptor (floor sink).  No p-trap is needed or desirable in this pipe.  The waste from the indirect drain receptor then needs to go through a grease catcher (I am not using the terms "grease interceptor" or "grease trap" on purpose).

The only "grease catcher" recognized by the IPC is a grease interceptor in accordance with the standards listed in 1003.3.4, which is what is show in the picture.  The problem is that those grease traps are really designed to be directly connected to a sink.  They rely on the head of the depth of the sink bowl and the tailpeice of the sink to get the proper flow through the interceptor.  See these typical Installation Instructions.  The problem is that to accept the waste from the floor sink, the grease trap needs to be below the bottom of the floor sink.

In every AHJ I have dealt with, the health department does not allow the "grease catcher" to be serviced inside the food preparation area, and so it must be located away from it's associated fixture.  The extra length of pipe and the minimal head available make a code compliant grease interceptor that meets the manufacturer's installation instructions almost impossible to install.  Fortunately, these AHJs also conviently ignore 1003.3.4 and allow the large, outdoor inground, precast concrete type of grease *traps*.  Thus, the conflict of how to install a grease interceptor after a floor sink never comes up.

This arrangement will work great at catching grease because the grease interceptor is installed the way the manufacturer intended.  One might make the argument that the intent of the IPC is to make sure that sewer gasses and back-ups from the building can not possibly get into the food prep sink, and that the pictured arrangment takes care of that.  However, the floor sink will now get the nasty effluent splashing in from the interceptor, and the food prep sink is directly connected to the nasty interceptor.


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## Rider Rick (Mar 10, 2010)

Re: Backflow preventer instead of air gap

Thank you to everyone that replied.

I am going to have the plumber remove and replace to meet code. I will keep you posted.

That you,

Rick


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## Rider Rick (Mar 15, 2010)

Re: Backflow preventer instead of air gapIMG_0053.JPG3.JPG[/attachment:2uy42kpk]Follow up: Plumber provied air gap at sink and plumbed grease trap in crawl to catch waste water from all sinks.Rick

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## skipharper (Mar 15, 2010)

Re: Backflow preventer instead of air gap

Are those glue joints between ABS and PVC?


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## Rider Rick (Mar 15, 2010)

Re: Backflow preventer instead of air gap

skipharper,

I'm not sure because I have not done the inspection yet, just received the photos from the plumber from e-mail.

Should I look for glue that can be used on ABS and PVC?

Rick


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## skipharper (Mar 15, 2010)

Re: Backflow preventer instead of air gap

I do not know of any glue that will connect the two materials


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## hlfireinspector (Mar 15, 2010)

Re: Backflow preventer instead of air gap

Access to clean out grease trap?


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## Rider Rick (Mar 16, 2010)

Re: Backflow preventer instead of air gap



			
				hlfireinspector said:
			
		

> Access to clean out grease trap?


Good question.

The plumber didn't want to install the grease trap there because it would be hard to service but that is the only place that would work as per code.

See the first photo, that was the plumbers pick.

Rick


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## Dr. J (Mar 16, 2010)

Re: Backflow preventer instead of air gap

Geeze, ya want it all don't ya?  Meet code? Access interceptor? Make interceptor intercept grease?  Keep nasty smells out of kitchen?


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## Daddy-0- (Mar 28, 2010)

Re: Backflow preventer instead of air gap

Access to the grease trap must be provided so they can clean it. Skip seems to have a good handle on the requirements here. JMHO


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## 88twin (Apr 1, 2010)

3c sink - air gap - floor sink - grease trap - backwater valve (if required)

we don't always use backwater valves.


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## DAYWALKER (Apr 2, 2010)

Just out of curiousity................how was this interceptor sized. Now that multiple sinks are connected......was flow taken into consideration?


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## DAYWALKER (Apr 2, 2010)

Just out of curiousity..................how was the interceptor sized? Now that multiple siks are connected.......was flow taken into consideration?


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## DAYWALKER (Apr 2, 2010)

Y'all be patient with me.......i'll get the hang of this.


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## peach (Apr 3, 2010)

Rick Taylor said:
			
		

> [attachment]3-8-2010 001.jpg1.jpg[/attachment]New restaurant with food prep sink drain to backflow preventer to grease trap to floor sink.
> 
> I think the sink needs an air gap between the sink and pee-trap.
> 
> ...


Shouldn't it be sink/airgap/floor sink or drain/grease trap?

The grease trap is often times located outside the building (especially with heavy frying).. so it can be serviced.


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## Moscow (Apr 5, 2010)

I am wondering why you have a grease trap on a food prep sink? Food prep sink/airgap/floor sink. Pots and pans sink/flow restricter/air gap/floor sink/grease trap


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