# 3 compartment sink in restaurant -DFU count?



## UALocal1Plumber

Hi everyone I'm just doing the load takeoff for a restaurant...

I have a three compartment sink that will be used for washing dishes. Although the code says that I can tie them together using a single trap, as long as the bowls are not more than 30" apart, my DFU count has to take into account all three bowls being dumped at the same time, yes no? In other words, each bowl would have the value of a 2" sink, which is two, for a total of 6 DFU for the three compartment sink?

Or given that there is only one faucet that could be running in any bowl at any time, would you say that the faucet is the limiting factor, and the DFU count should just be 2?

Thanks,
Keith


----------



## MarkToo

If it's trap sizing you're trying to figure, code here reads 2" trap after you gang the third compartment in. That's it. Your code is likely very specific in this manner as well - should be easy to look up.

You may need to size an interceptor for grease though.


----------



## PrecisePlumbing

Probably not relevant to your code but i have asked the same exact question here and the answer i was given was count each individually. The dishpig could load each sink to capacity individually. Better to be over engineered than under imo


----------



## swedishcharm21

UALocal1Plumber said:


> Hi everyone I'm just doing the load takeoff for a restaurant...
> 
> I have a three compartment sink that will be used for washing dishes. Although the code says that I can tie them together using a single trap, as long as the bowls are not more than 30" apart, my DFU count has to take into account all three bowls being dumped at the same time, yes no? In other words, each bowl would have the value of a 2" sink, which is two, for a total of 6 DFU for the three compartment sink?
> 
> Or given that there is only one faucet that could be running in any bowl at any time, would you say that the faucet is the limiting factor, and the DFU count should just be 2?
> 
> Thanks,
> Keith


Use to be asked this ALL the time when I was an Inspector. Here it would be 2 DFU, but if you have a 2 inch outlet, than you already know how to run it from there. This is one of those things that need more clarity in the code book (IPC) As we all know, there are many things in the code book that leaves too much to interpretation.

Somewhat similar situation I would be asked for example would be a 2 valve, 2 head shower rough in, only one drain (2 inch trap) but how was it sized. That scenario, it would be 4 DFU, as long as the flow of each head was not over 5.7 GPM each.

Back to your 3 comp sink....check to see if your plumbing code and/or health dept requires you to have a solids interceptor BEFORE the grease interceptor if your 3 comp sink is calling for a commercial disposal.

Make sure you know exactly how you are going to run your wash, rinse and sanitize compartments. Usually the health dept has their own set of rules pertaining to 3 compartment sinks (at least here they do)

As we all know...every state and just about every municipality has different code and requirements.


----------



## plbgbiz

PrecisePlumbing said:


> ...The _*dishpig*_ could load each sink to capacity...


That was mean.


----------



## NYC Plumber

Should be indirect into a 3" FLoor sink.


----------



## Michaelcookplum

NYC Plumber said:


> Should be indirect into a 3" FLoor sink.


That's the ONLY way I would do it


----------



## Tim`s Plumbing

UALocal1Plumber said:


> Hi everyone I'm just doing the load takeoff for a restaurant...
> 
> 
> 
> I have a three compartment sink that will be used for washing dishes. Although the code says that I can tie them together using a single trap, as long as the bowls are not more than 30" apart, my DFU count has to take into account all three bowls being dumped at the same time, yes no? In other words, each bowl would have the value of a 2" sink, which is two, for a total of 6 DFU for the three compartment sink?
> 
> Or given that there is only one faucet that could be running in any bowl at any time, would you say that the faucet is the limiting factor, and the DFU count should just be 2?
> 
> Thanks,
> Keith


 By my code it would have to dump into either a 2 1/2" or 3" drain that goes into a grease intercepter if it is for washing pot and pan`s. Into a floor sink if it is a prep sink.


----------



## DesertOkie

Hell, I think we were first bay to Grease trap 2nd & 3rd to floor sink to main. It never made sense to me. But it was always what they wanted, not what was in the book or what made sense. It even varied on different sides of town.


----------



## TX MECH PLUMBER

By UPC. U tie them together with 2" and drain into floor sink. If the developed length of pipe is 5' or more you must have a trap and at or before 5' in the run. The trap doesn't need a vent and u must put clean outs at an Chang of direction and have an air gap at discharge You cannot tie it into any indirect waste pipe that is used for anything other then cleaning dishes and if u do vent it, the same rule applies !! If it's new construction or remodel. Install a 3 floor sink at one end of sink and tie all compartments together with 2"and use a combo on the high end for a clean out. It will drain like a champ !!


----------



## smoldrn

TX MECH PLUMBER said:


> By UPC. U tie them together with 2" and drain into floor sink. If the developed length of pipe is 5' or more you must have a trap and at or before 5' in the run. The trap doesn't need a vent and u must put clean outs at an Chang of direction and have an air gap at discharge You cannot tie it into any indirect waste pipe that is used for anything other then cleaning dishes and if u do vent it, the same rule applies !! If it's new construction or remodel. Install a 3 floor sink at one end of sink and tie all compartments together with 2"and use a combo on the high end for a clean out. It will drain like a champ !!


That's how I do mine, works great.


----------



## justin

oh yeah, and be sure u put santees on there back , or pressure tees since they are basically same on there back. lol. 

use combos , only!!


----------



## UALocal1Plumber

NYC Plumber said:


> Should be indirect into a 3" FLoor sink.


The code pretty clearly states that an air gap is only needed for food prep. Is cleaning dishes considered prep? If I do dump into a floor sink, can I triple the three bowls together with no trap?

Keith


----------



## mccmech

Tim`s Plumbing said:


> By my code it would have to dump into either a 2 1/2" or 3" drain that goes into a grease intercepter if it is for washing pot and pan`s. Into a floor sink if it is a prep sink.



If you would, please educate me a bit. When you install your 3-bay into a 3" trap which then goes through a grease-trap, do you utilize the cast-iron flow regulator which comes with the grease trap? I have found that the regulator ( the one with the vent off the side of it ) chokes the flow down so much that my 3" trap will still get overwhelmed if any more than 1 fully loaded bowl is let go at a time. I never had had any problem on my prep sinks which indirectly drain full flow into a floor sink with 3" trap directly to waste. Just trying to learn how others deal with that traffic-jam that is the flow-regulator fitting. Thanks for any input.


----------



## jimmyb21

In WSSC's territory (Washington Suburban Sanitary Commission, PG & Montgomery counties, MD) we have to reduce each tailpiece on each compartment to 1/2" & provide an airgap where it dumps into the main trunk line. This in theory slows the water going through the grease trap along with the flow restrictor. The main trunk line can be 2" or 3" depending on the size of the compartments & how the inspectors feeling that day :laughing:. Typically, we'll pipe everything into a floor sink if one is available but it can be piped directly into a drain at the wall & they will not allow a commercial disposal at all. They're also strict about grease abatement so a trap or outdoor interceptor is a must.

They've been giving out FOG violations left & right to everybody, restaurants, churches, etc. I think it's kind of messed up that they treat a church that cooks 2 meals a year the same as KFC

DC on the other hand, you don't need to reduce the tailpieces & can tie directly to each compartment. You can have a commercial disposal as long as it doesn't go through grease abatement equipment. DC's like the wild west in comparison to WSSC :yes:


----------



## TX MECH PLUMBER

UALocal1Plumber said:


> The code pretty clearly states that an air gap is only needed for food prep. Is cleaning dishes considered prep? If I do dump into a floor sink, can I triple the three bowls together with no trap?
> 
> Keith


 By my code yes as long as the run isn't longer then 5'. If it us u must have a trap !!


----------



## user7551

Just about everywhere in the state of Texas you will have an air gap on any indirect waste it help's protect the equipment from sewer back up. Its not just in our plumbing code but is actually in the state health code.


----------



## PrecisePlumbing

plbgbiz said:


> That was mean.


Too true biz. Too true. I should have been less specific. The apprentice dishpig might get a shot too!


----------



## Tim`s Plumbing

mccmech said:


> If you would, please educate me a bit. When you install your 3-bay into a 3" trap which then goes through a grease-trap, do you utilize the cast-iron flow regulator which comes with the grease trap? I have found that the regulator ( the one with the vent off the side of it ) chokes the flow down so much that my 3" trap will still get overwhelmed if any more than 1 fully loaded bowl is let go at a time. I never had had any problem on my prep sinks which indirectly drain full flow into a floor sink with 3" trap directly to waste. Just trying to learn how others deal with that traffic-jam that is the flow-regulator fitting. Thanks for any input.


 We tell the owners of the restaraunt that is the way it will drain because that is what are code requires to have a grease interceptor at the fixture to protect the lines inside the building from grease the interceptor out in the parking lot is for protecting the city sewer. We don`t design the interceptors we only install the according to code. 

The newest thing here is a interceptor with a built in skimmer and grease heater.


----------



## user7551

Tim`s Plumbing said:


> We tell the owners of the restaraunt that is the way it will drain because that is what are code requires to have a grease interceptor at the fixture to protect the lines inside the building from grease the interceptor out in the parking lot is for protecting the city sewer. We don`t design the interceptors we only install the according to code.
> 
> The newest thing here is a interceptor with a built in skimmer and grease heater.



Let me ask you a question do you also install the little interceptors on floor drains on all prep floors also . If not then the interceptors on the fixture's themselves would be pointless to protect the lines inside the building that are already on a grease line plus any handsinks in the prep area we all know they never get grease down them at all . What code are you under, just curious.


----------



## NYC Plumber

UALocal1Plumber said:


> The code pretty clearly states that an air gap is only needed for food prep. Is cleaning dishes considered prep? If I do dump into a floor sink, can I triple the three bowls together with no trap?
> 
> Keith


I would say yes and yes. Ive never seen a trple compartment sink direct connected.


----------



## UALocal1Plumber

NYC Plumber said:


> I would say yes and yes. Ive never seen a trple compartment sink direct connected.


10-4 thanks very much for the input.


One more question. The restaurant owner is asking for convenience that we install the grease trap a long way down from where the kitchen itself is... to give a little background, this is a restaurant tenant on the first floor of a large office facility. I plan on routing everything so that it joins up in the ceiling of the basement, and it will travel about 85 feet down a hallway where an adequately sized stack is located to drop into. The stack is also located by a loading dock door. 

The restaurant is asking me to locate the grease trap at the end of the 85 foot run, just as it ties into the stack so that it will be easier to clean the trap during working hours, and so it's closer to the loading dock where they can put the grease out for pickup. It makes sense and one of their biggest concerns is from experience at another restaurant - the trap was in the kitchen and stunk out the whole place whenever they tried to clean it. 

So long story short, we would have a grease bearing line traveling 85' to a grease trap. Does anyone see a problem with that?

Thanks so much,
Keith


----------



## TX MECH PLUMBER

Hmm. I'd have to check my code but I know I've seen grease lines longer then that !! Check ur local code


----------



## plbgbiz

UALocal1Plumber said:


> So long story short, we would have a grease bearing line traveling 85' to a grease trap. Does anyone see a problem with that?


Not if they own a jetter.


----------



## user7551

We put in grease systems that are 1000's of feet long, the issues that come to mind are cleaning and maintenance issues


----------



## UALocal1Plumber

plbgbiz said:


> Not if they own a jetter.



HAHAHA actually _I_ own the jetter and I'm sure my services will be needed deep into the future! The restaurant is more concerned about the smell of the trap than the money to maintain the line, so I'm in luck with that one. 

I checked the code and didnt' see anything amiss. But of course I'm just checking with the pros.

Keith


----------



## Tim`s Plumbing

playme1979 said:


> Let me ask you a question do you also install the little interceptors on floor drains on all prep floors also . If not then the interceptors on the fixture's themselves would be pointless to protect the lines inside the building that are already on a grease line plus any handsinks in the prep area we all know they never get grease down them at all . What code are you under, just curious.


 I am going by the Massachuetts plumbing code. Their thinking is the majority of the grease comes from 3 bay sinks and dish washers. I don`t make the code I only install according to code.


----------



## NYC Plumber

UALocal1Plumber said:


> 10-4 thanks very much for the input.
> 
> One more question. The restaurant owner is asking for convenience that we install the grease trap a long way down from where the kitchen itself is... to give a little background, this is a restaurant tenant on the first floor of a large office facility. I plan on routing everything so that it joins up in the ceiling of the basement, and it will travel about 85 feet down a hallway where an adequately sized stack is located to drop into. The stack is also located by a loading dock door.
> 
> The restaurant is asking me to locate the grease trap at the end of the 85 foot run, just as it ties into the stack so that it will be easier to clean the trap during working hours, and so it's closer to the loading dock where they can put the grease out for pickup. It makes sense and one of their biggest concerns is from experience at another restaurant - the trap was in the kitchen and stunk out the whole place whenever they tried to clean it.
> 
> So long story short, we would have a grease bearing line traveling 85' to a grease trap. Does anyone see a problem with that?
> 
> Thanks so much,
> Keith


Ive seen that its actually pretty common, sometimes they heat trace the grease waste lines.
Only thing code says is you cant dump into public sewer, as long as it doesn't cost the city money they dont care how you maintain it.


----------



## suzie

Pot or scullery sink here is 4FU/dishcarge capacity of 16 to 30 gpm. minimum trap size 2" no matter how you configure within code requirements


----------



## UALocal1Plumber

NYC Plumber said:


> Ive seen that its actually pretty common, sometimes they heat trace the grease waste lines.
> Only thing code says is you cant dump into public sewer, as long as it doesn't cost the city money they dont care how you maintain it.


Thanks for the info!

Keith


----------



## NYC Plumber

UALocal1Plumber said:


> Thanks for the info!
> 
> Keith


No problem, let us know how you make out!


----------



## Caduceus

In my area, all 3 compartment sinks in restaurants must have a 2" trap for each compartment and each trap must be vented. The drains will connect together and tie into a grease interceptor. The grease interceptor will be sized according to the dimensions of the sink compartments with a minimum 25 gpm grease interceptor. A vented flow restrictor will be installed before the grease trap as well as a vent after the grease trap to prevent vapor lock. In areas where food handling, storage or preparation occur, only semi-automatic or automatic grease interceptors are accepted. 'Prep sinks' that have a food waste grinder will have a separator and also connect to the grease trap, which will affect the sizing of the grease interceptor in addition to the 3 comp. sink. A maintenance agreement must also be obtained and contract copy provided for the servicing of the grease trap.


----------



## mccmech

Caduceus said:


> In my area, all 3 compartment sinks in restaurants must have a 2" trap for each compartment and each trap must be vented. The drains will connect together and tie into a grease interceptor. The grease interceptor will be sized according to the dimensions of the sink compartments with a minimum 25 gpm grease interceptor. A vented flow restrictor will be installed before the grease trap as well as a vent after the grease trap to prevent vapor lock. In areas where food handling, storage or preparation occur, only semi-automatic or automatic grease interceptors are accepted. 'Prep sinks' that have a food waste grinder will have a separator and also connect to the grease trap, which will affect the sizing of the grease interceptor in addition to the 3 comp. sink. A maintenance agreement must also be obtained and contract copy provided for the servicing of the grease trap.


So, if I understand correctly, you will have three 2" traps dumping indirectly into a floor sink, which then goes through a flow restrictor? How do you, given that set-up, prevent the floor sink from backing up & flooding the floor. The volume of water dumping has GOT to overwhelm the floor sink, no?


----------



## Caduceus

mccmech said:


> So, if I understand correctly, you will have three 2" traps dumping indirectly into a floor sink, which then goes through a flow restrictor? How do you, given that set-up, prevent the floor sink from backing up & flooding the floor. The volume of water dumping has GOT to overwhelm the floor sink, no?


No, there are three, 2" traps-vented. They connect into a single horizontal drain that has a vented flow restrictor before entering a floor mounted grease trap. This description was for small restaurant installation with individual grease interceptor (25 or 35 GPM, etc.)


----------



## Caduceus

I guess it was never really clear, unless I missed it, whether this is for a common grease interceptor such as in a food court or strip mall with dedicated grease lines from multiple locations or an individual restaurant with a floor mounted interceptor.


----------



## swedishcharm21

Caduceus said:


> In my area, all 3 compartment sinks in restaurants must have a 2" trap for each compartment


So are you saying that running indirect waste with 3 compartment sinks in your municipality is prohibited? Do you have any pics of the set up described above? You used the word "must" so I am looking for some clarity.


----------



## Dmaz

I got into an argument with my instructor over 3 compartment sinks when I was in 4th year. He said any 3 compartment sink with common trap should be 2". I argued that if a sink has a larger f.o.p than 1 1/2 that the trap is sized one size larger than the largest f.o.p. He still says I'm wrong. 

I still disagree. Here's the code clause, what do you guys think


----------

