# grease traps commercial venting



## ciropat (Jan 25, 2014)

I will thank in advance anyone who replies to my question if u have a double comp. sink for dish washing. and u are using the grease trap as the trap for the fixture.do u need a vent ,on the outlet side ,of the grease trap if,their is a vent on the inlet side for the fixture plus the air intake on the flow control valve all,getting tied into a dry vent. on intlet side of the grease trap.


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## Tommy plumber (Feb 19, 2010)

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## redbeardplumber (Dec 4, 2012)

^^^


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## MTDUNN (Oct 9, 2011)

If you're a plumber please introduce yourself. If not, I see a Padlock in your future


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## ciropat (Jan 25, 2014)

now I have always put one in on the outlet side but im having a debate with someone they say no I say yes cause u always vent before the trap and the grease trap is considered a trap


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## Ghostmaker (Jan 12, 2013)

A grease trap is a interceptor. It is mis named by old plumbers.


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## Ghostmaker (Jan 12, 2013)

Also the flow control air intake is not a plumbing vent.


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## ciropat (Jan 25, 2014)

Yea i know if u read the post i di think i called it the intake so the grease dont cogulate i was talking about a vent on outlet side if there is one on inlet a vent not the flow control intake


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## plbgbiz (Aug 27, 2010)

Ghostmaker said:


> A grease trap is a interceptor. It is mis named by old plumbers.


It believe it was originally misnamed by the manufacturers and code books.


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## Plumb Bob (Mar 9, 2011)

ciropat said:


> I will thank in advance anyone who replies to my question if u have a double comp. sink for dish washing. and u are using the grease trap as the trap for the fixture.do u need a vent ,on the outlet side ,of the grease trap if,their is a vent on the inlet side for the fixture plus the air intake on the flow control valve all,getting tied into a dry vent. on intlet side of the grease trap.


Where I come frome they use a three compartment snk for dishwashing. Two compartment would be a prep sink.


Something seems not right....


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## MTDUNN (Oct 9, 2011)

Plumb Bob said:


> Where I come frome they use a three compartment snk for dishwashing. Two compartment would be a prep sink. Something seems not right....


I was thinking the same. Why are you using grease trap on a 2 compartment?


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## plbgbiz (Aug 27, 2010)

The inspectors here will require the interceptor based on likely use rather than number of compartments. I have been required to install them even on single compartment sinks when it was to be used for food prep.


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## MTDUNN (Oct 9, 2011)

Then I would think a fixture vent before the GT then flow control. And vent on outlet


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## Ghostmaker (Jan 12, 2013)

plbgbiz said:


> It believe it was originally misnamed by the manufacturers and code books.



Both:laughing:


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## Caduceus (Mar 1, 2012)

Intended use, as plbgbiz stated, is the most important detail. Generally a 3 compartment sink is implied as needing an 'interceptor' by design. Y'know....rinse, wash, sanitize, by food service standards which influences plumbing downstream.
In my area, each compartment must have a trap.
Each trap must be vented independently. 
The diffuser before the inerceptor must have a vent.
After the diffuser a vent must be installed.
All of the vents can connect to a common vent if the lowest connection is no less than 6" above the flood level rim of the fixture being served (the two compartment sink in your case).
If it is an automatic or semi-automatic grease interceptor, the vent will be after the outlet valve.


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