# Grease trap help...



## Plumbducky (Jun 12, 2010)

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Grease trap help... *

Just installed a new Schier grease trap today for a dishwasher. Had inspection and everything is sized properly. When the dishwasher drains after its cycle it overflows the receptor. The recepter is a 2" standpipe and is 14" tall per code. If I were to reduce the outlet size of the dishwasher to 1 1/4" do you think that it will slow down the drain enough to keep it from overflowing? Any help would be appreciated. The standpipe increases by means of a 3x2 coupling and the drain is air breaked.​


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## SlickRick (Sep 3, 2009)

If it is a commercial DW, The flow restrictor will have a hard time keeping up. The velocity of the flow rate is going to create turbulence in the restrictor. If the DW is very close to the restrictor, I can't see it keeping up.


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## plbgbiz (Aug 27, 2010)

SlickRick said:


> ...If the DW is very close to the restrictor, I can't see it keeping up.


I'm with Rick on this one. It would take a pretty good sized interceptor to keep up with a commercial DW close by. Maybe even a long way away. The GPM's hit pretty hard and heavy on discharge.


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## Plumbducky (Jun 12, 2010)

It is a comm DW and the amount of pipe on the inlet side is 1 lt 90, vent tee and trap. Total amount of pipe is 5".


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## plbgbiz (Aug 27, 2010)

That's pretty close. If you restrict the DW flow enough to make a difference, you may be causing some damage down the road to the pump (maybe).


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## SlickRick (Sep 3, 2009)

Plumbducky said:


> It is a comm DW and the amount of pipe on the inlet side is 1 lt 90, vent tee and trap. Total amount of pipe is 5".


Houston, we have a problem.


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## Redwood (Sep 8, 2008)

Sounds like the intercepter is too small... :whistling2:


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## SlickRick (Sep 3, 2009)

Redwood said:


> Sounds like the intercepter is too small... :whistling2:


Sounds like a required retro-fit that meets city requirement, but won't handle the flow rate, then the flow restrictor is removed ,and then you have a useless POS.


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## easttexasplumb (Oct 13, 2010)

If the dish machine dumps into a tray and then to the interceptor, restricting the drain flow may make the tray overflow. I installed 12" by 12" 18" deep floor sinks for a dishmachine, and it would barely keep up with the flow. Good luck.


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## Widdershins (Feb 5, 2011)

easttexasplumb said:


> If the dish machine dumps into a tray and then to the interceptor, restricting the drain flow may make the tray overflow. I installed 12" by 12" 18" deep floor sinks for a dishmachine, and it would barely keep up with the flow. Good luck.


 I've run in to this before. I 'corrected' the problem by installing a 4" floor sink and an oversized dump tray.

I still had access from the parking garage below, of course.

Your mileage may vary.


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## Evolve (Jan 2, 2011)

Did you make sure you had a flow control device?

It's a fitting that is installed on the inlet side of the interceptor to limit the velocity of the water through the interceptor. It also helps to ensure that the grease doesn't flow through the interceptor and into the drainage.
Or like Redwood mentioned, the interceptor maybe too small.


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## Eric (Jan 10, 2011)

When we have to install a trap here we use the formula of 2-LB of grease retention for each GPM of flow. I don't know what you guys do on the other side, maybe that, maybe something else. So with that in mind, I would have gotten the GPM rating of the DW from the spec sheet or manufacture, and sized the trap by that number.

Now you have to look at the temp of the water discharging out of the DW. If it's over 150°F, is the grease inteceptor doing anything?


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## U666A (Dec 11, 2010)

Evolve said:


> Did you make sure you had a flow control device?
> 
> It's a fitting that is installed on the inlet side of the interceptor to limit the velocity of the water through the interceptor. It also helps to ensure that the grease doesn't flow through the interceptor and into the drainage.
> Or like Redwood mentioned, the interceptor maybe too small.


Was thinking the same thing... Is it gravity drainage from a pan or is it pumped?

If pumped, I would try to loop the discharge up as high as possible, and install a secondary flow control fitting on the vertical leg of the gravity discharge side...


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## Plumbducky (Jun 12, 2010)

The dw is chemical based and not temp based. The grease trap is a 15 gpm trap. The diswasher water discharge is 1.2 gpm per the manufacturer. I am going back today and will figure out a solution.

The dw is gravity discharge, not pumped.


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## plumb nutz (Jan 28, 2011)

Can this particular interceper be used as a trap? If it could then you could just tie in directly from the dish washer.

I also have a larger standpipe before. With a 2" trap and 2"x3" reducer and 3" standpipe to accept the volume. But that's when somebody f-ed up and didn't size according to volume.
Increasing the pipe length should help as well.


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## NYC Plumber (May 4, 2011)

Maybe it's me but why is a dishwasher discharging into a grease trap?
The pre rinse sink should go to the grease trap, not the dishwasher itself.


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## SlickRick (Sep 3, 2009)

NYC Plumber said:


> Maybe it's me but why is a dishwasher discharging into a grease trap?
> The pre rinse sink should go to the grease trap, not the dishwasher itself.


I was reading Wisconsin's reg's. Some jurisdictions require the DW to run through the GT.


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## NYC Plumber (May 4, 2011)

Why though it makes no sense. There should be no grease in the dishwasher, dishes should be rinsed before they go to dishwasher.
My opinion... your just dumping a lot of hot water into the grease trap and asking for problems.


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## SlickRick (Sep 3, 2009)

NYC Plumber said:


> Why though it makes no sense. There should be no grease in the dishwasher, dishes should be rinsed before they go to dishwasher.
> My opinion... your just dumping a lot of hot water into the grease trap and asking for problems.


I don't know if I can find the article, but the same reg. that required the DW, warned that it could impede the function of the GT.


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## Widdershins (Feb 5, 2011)

NYC Plumber said:


> Why though it makes no sense. There should be no grease in the dishwasher, dishes should be rinsed before they go to dishwasher.
> My opinion... your just dumping a lot of hot water into the grease trap and asking for problems.


 As noted earlier, it's a chemical dishwasher -- Temps shouldn't be over 120.


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## plumb nutz (Jan 28, 2011)

And even if they are slightly higher than that I was told "if the drain is run I'm metal pipe (C.I. or DWV cp.) The water temp drops rapidly as not to affect it too much.

In this backwards state is not a plumbing code but health dept. regulation, which depends on where you are at.


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## Plumbducky (Jun 12, 2010)

NYC Plumber said:


> Maybe it's me but why is a dishwasher discharging into a grease trap?
> The pre rinse sink should go to the grease trap, not the dishwasher itself.


 
It gets even better, the rinse sink before the dw has a disposer on it. So all of the dishes get sprayed off with hot water and then into the dw. When installing it all yesterday I found one blob of grease the size of a nickel. The rest of line was clear. The City required the only 2 restaurants on this section of sewer to have grease traps installed. I believe that all of the residential connections on this line should also have grease traps. This restaurant has been around 20+ years.


I found out that the flow restricter on the inlet was not cut out all of the way from the manufacturer. The dw drains just fine now.


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## Marlin (Aug 14, 2008)

Glad you solved it and it was something simple. 

We have a similar situation with the grease traps. The county took over my towns sewer department and they're now forcing all the restaurants to install grease traps on their dishwashers. They go one step further though and require a special grease trap that has a heating element and a potable water line to flush it out. I forget what it's called, it's been a year or so since we installed one. The thing runs thousands of dollars and depending on the existing setup can be a really big ordeal to install.


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## SlickRick (Sep 3, 2009)

Plumbducky said:


> It gets even better, the rinse sink before the dw has a disposer on it. So all of the dishes get sprayed off with hot water and then into the dw. When installing it all yesterday I found one blob of grease the size of a nickel. The rest of line was clear. The City required the only 2 restaurants on this section of sewer to have grease traps installed. I believe that all of the residential connections on this line should also have grease traps. This restaurant has been around 20+ years.
> 
> 
> I found out that the flow restricter on the inlet was not cut out all of the way from the manufacturer. The dw drains just fine now.


I'll have to remember that one. :thumbup:


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## Redwood (Sep 8, 2008)

SlickRick said:


> I'll have to remember that one. :thumbup:


In the trade that is known as the Grease Trap Size Multiplier.... :laughing:


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## Tommy plumber (Feb 19, 2010)

Reading these last few posts put a smile on my face, who is going to clue in the boy?..."The flow restrictor wasn't cut out by the manufacturer." That's a good one....:laughing:


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## bartnc37 (Feb 24, 2009)

Hey maybe the factories cnc machine had the wrong bit in it:thumbup:


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## plumb nutz (Jan 28, 2011)

Tommy plumber said:


> Reading these last few posts put a smile on my face, who is going to clue in the boy?..."The flow restrictor wasn't cut out by the manufacturer." That's a good one....:laughing:


Going to ask the same thing...

So he removed the restricting in flow restricter?


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