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Garbage disposal not to interceptor?

jim baird

jim baird

Silver Member
Joined
Oct 17, 2009
Messages
490
Location
Comer, GA
Among plumbing notes on plans, MEP engineer's plans say "Waste from garbage disposers shall not drain to grease interceptor." Ergo double sink has one side going to grease trap, other side (w/GD) to sanitary drain.

Plumber says it's crazy, I am scratching my head.

What's the rationale for this?
 
Welcome,

Is this a under the counter grease trap? If so and you are under the UPC section 1015 states Unless specifically required or prmitted by the AHJ, no food waste disposal unit or dishwasher shall be connected to or discharge into any grease trap. Now if it is the outside interceptor then the garbage disposer and dishwasher can run to it.

If it is a under the counter type I would not let the garbage disposer go to the grease trap it will plug up really quick.
 
Thanks Moscow.

This is IPC land. Grease trap is sized according to EPA formula.

EPA 1 Procedure Formula (# of meals X (4.5) X kitchen loading B KL = trap volume (gal)

Kitchen Loading KL

Food Grinder & Dishwasher 2.50

Without Food Grinder 2.00

Without Dishwasher 1.50

Without Food Grinder & DW 1.00

Engineer specs 1500 gal outside tank, as formula calls for 1100+gal.

(Formula is contained in local ordinance, which curiously mixes up the terms Interceptor and Grease trap)
 
I am not up on the IPC however I would say there is no problem running everything but the bathroom to the 1500 gal out side tank. We do this all the time here that is why I try and talk them into installing an out side tank much easer to plumb.

Good Luck

Justin
 
This is from IPC'06:

1003.3.2 Food waste grinders. Where food waste grinders

connect to grease interceptors, a solids interceptor shall

separate the discharge before connecting to the grease interceptor.

Solids interceptors and grease interceptors shall be

sized and rated for the discharge of the food waste grinder.

Emulsifiers, chemicals, enzymes and bacteria shall not discharge

into the food waste grinder.

IPC defs say, however, that an interceptor is part of the sanitary drain system:

GREASE INTERCEPTOR. A plumbing appurtenance that

is installed in a sanitary drainage system to intercept oily and

greasy wastes from a wastewater discharge. Such device has

the ability to intercept free-floating fats and oils.

IPC says the sanitary drain system extends only to a point 30" outside the building, at which point the label changes to "building sewer".

Best I can tell the big grease trap is more than 30" outside.
 
If the dicharge into the waste grinder is required to discharge into a grease interceptor per 1003.3.1 it cannot discarge into the sanitary drain system ahead of the grease interceptor. In addition it must first go through the solids interceptor as you have shown in Secton 1003.3.2. It appears that the MEP engineers note is incorrect, unless I'm missing something.

GPES
 
Thanks GPE.

My reading of 1003.3.1 does not tell me that the GD would be necessarily included among the fixtures that section requires to pass through grease trapping.

In a common sense vein, also, if whatever content does pass through a waste grinder, how "solid" is it then?

In another wrinkle regarding this design, the proposed kitchen is called a "catering" kitchen, where no actual "cooking" goes on, just "food warming". (This labeling relieves designers from calling for full commercial hood setup)

My question is why we have a waste grinder at all, since I associate that with food prep more than with dishwashing.
 
I'm just saying that if it has been determined that one side of a double sink is required to discharge into a grease intercepor, it stands to reason that the other side of the double sink would have that same requirement.

The fact that a food waste grinder has been installed would not negate the requirement that it discharge into the interceptor, only that it must pass through a solids interceptor first.

Hey! This is my 100th posting. I must be a Senior Member!

GPES
 
Congrats on your upgrade in status, GPE. Nothing like another feather for the cap, huh?

I am copying below part of the project architect's reply to my query about this design. It appears to me that some of the kitchen features were added despite the architect's recommendations.

Most catering kitchens that we have installed have microwave ovens but no

stoves or standard ovens. A double bowl sink, without a garbage

disposal, would exist to provide water for service and operation but

typically no dishwashing capability is provided. The food for the

catering kitchen is brought in to a facility in warming/cooling carts

that are plugged in to maintain desired temperature. All waste is

scraped into waste bins and removed from the site and all dishes are

removed by the catering company for cleaning at their facilities.

The choice between catering kitchen versus cooking kitchen has typically

been a choice for the Owner between upfront financial expense and a

potential operational limits of a property. Most Owners typically

choose the catering kitchen option as the frequency of big food events

is typically limited.
 
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Sounds like the MEP engineer and the project architect need to get on the same page
and design according the adopted code in your AHJ.

With all of the different kinds of communication forms available these days, it seems
like there is less and less and less actual communicating going on, ...at least in the
construction industry. D`OH !!
.
 
Moscow wrote: "Is this a under the counter grease trap? If so and you are under the UPC section 1015 states Unless specifically required or prmitted by the AHJ, no food waste disposal unit or dishwasher shall be connected to or discharge into any grease trap. Now if it is the outside interceptor then the garbage disposer and dishwasher can run to it."

Moscow, It states in the 2006 UPC section 1014 that these items are not to drain into a grease interceptor, which would include the kind outside the building.

I've always thought that the grease trap under the counter was more of a concern with the grease being heated by the dishwasher, than would a large interceptor outside the building. However, the interceptor is not to receive from dishwashers or garbage disposals.
 
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This just in re OP.

Job was past design and into bid process by time of my arrival on scene.

Seems person in charge (now retired) had insisted over architect's warnings, on residential cooking appliances, residential DW, and waste grinder to be included in "catering kitchen".

Architect, when poked re problem, recommended eliminating all three items and grease trap, with reminder that in catering kitchen mode, sink is for handwashing and service only.

BTW, I can find no reference to "catering kitchen" as a definition in I-codes.

Anyone here know of a code that does?
 
Thanks for the link, Jmorrison.

The mystery lies, however, not in grease traps but in the def of the term, "catering kitchen".

Does it deserve a new thread?
 
Glennman CBO said:
Moscow wrote: "Is this a under the counter grease trap? If so and you are under the UPC section 1015 states Unless specifically required or prmitted by the AHJ, no food waste disposal unit or dishwasher shall be connected to or discharge into any grease trap. Now if it is the outside interceptor then the garbage disposer and dishwasher can run to it."Moscow, It states in the 2006 UPC section 1014 that these items are not to drain into a grease interceptor, which would include the kind outside the building.

I've always thought that the grease trap under the counter was more of a concern with the grease being heated by the dishwasher, than would a large interceptor outside the building. However, the interceptor is not to receive from dishwashers or garbage disposals.
Click to expand...
I sorry I should of told you we are still under the 2003 UPC and that is were I pulled the section out of. I have and still will allow as long as you install the right size out side grease interceptor to have all but the bathrooms to go through the interceptor, we have some that are 10 to 15 years old no problem yet.

Justin
 
Talk to the MEP engineer since he will need to modify his drawings if you want to do it different. I know this is heresy but some times an engineer knows more that an inspector or the building official.

It seems like the owners representative gave instructions that resulted in the current design. Thus if you now acting as the owner's representative wants to change it at this time and if what you want to do is code compliant you will need to pay the Architect and the MEP engineer to modify their designs and you will need to pay the contractor to make the changes. You will also need to pay the jurisdiction any fees to modify the permit documents.
 
Mark K said:
Talk to the MEP engineer since he will need to modify his drawings if you want to do it different. I know this is heresy but some times an engineer knows more that an inspector or the building official.

It seems like the owners representative gave instructions that resulted in the current design. Thus if you now acting as the owner's representative wants to change it at this time and if what you want to do is code compliant you will need to pay the Architect and the MEP engineer to modify their designs and you will need to pay the contractor to make the changes. You will also need to pay the jurisdiction any fees to modify the permit documents.
Click to expand...

That's funny, I need to pay to get the designer to produce code compliant documents.....
 
The only thing that should enter the grease interceptor or trap is water with: fats, oils and grease.
Food scraps belong in the trash.

Using hot water, 120 degrees F or higher to rinse the dishes or if a dishwasher is connected, keeps the grease in suspension and does not allow for separation. If the trap does not have sufficient capacity to allow for cooling grease (such as a grease trap) it will again be discharged into the sewer. Even if the grease amount isn’t a lot as it cools it accumulates on the interceptor pipe walls and causes a plug. Hot grease cools quickly in a sanitary sewer.upload_2020-4-21_6-45-42.png
 
Unfortunately I don't have a picture but you can take my word for this: I have seen receptacle and switch outlet boxes packed with grease in a commercial kitchen.
 
jim baird said:
Thanks GPE.

My reading of 1003.3.1 does not tell me that the GD would be necessarily included among the fixtures that section requires to pass through grease trapping.

In a common sense vein, also, if whatever content does pass through a waste grinder, how "solid" is it then?

In another wrinkle regarding this design, the proposed kitchen is called a "catering" kitchen, where no actual "cooking" goes on, just "food warming". (This labeling relieves designers from calling for full commercial hood setup)

My question is why we have a waste grinder at all, since I associate that with food prep more than with dishwashing.
Click to expand...

Caterer's often "prep" foods, especially salads and veggies and fruit plates.
 
2019 CALIFORNIA PLUMBING CODE
1014.1.3 Food Waste Disposers and Dishwashers
No food waste disposer or dishwasher shall be connected to or discharge into a grease interceptor. Commercial food waste disposers shall be permitted to discharge directly into the building's drainage system.
Exception: Food waste disposers shall be permitted to discharge to grease interceptors that are designed to receive the discharge of food waste.

International Plumbing Code 2015
1003.3.2 Food Waste Disposers
Where food waste disposers connect to grease interceptors, a solids interceptor shall separate the discharge before connecting to the grease interceptor. Solids interceptors and grease interceptors shall be sized and rated for the discharge of the food waste disposers.
Emulsifiers, chemicals, enzymes and bacteria shall not discharge into the food waste disposer.
 
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