# Air bound vent sizing for grease interceptor



## markb (Jun 11, 2009)

What does the Ontario building code say about minimum air bound vent (vent on inlet side) size for a grease interceptor? 

I can't seem to find anything, but stack elevation drawings in the back of the OBC show some with 1.25" clean outs on air bound vents, and 1.5" anti siphon vents. Are they 1.25 on all installs, because they are only preventing the GI from becoming air bound? Or is it based on largest trap being served? 

Any help would be appreciated before I get into a discussion with an inspector.

Sent from my iPod touch using PlumbingZone


----------



## plumber666 (Sep 19, 2010)

ASPE Data Book, Volume 4, Chapter 8, Grease Interceptors. That's the only note in the appendix of the BC Code I can find, and it speaks to the design, sizing and installation of them. I've never seen or read it before.

I've installed several of them, but many more oil interceptors. Oils ones are clearly discussed in the Code. With the exception of one, I haven't done any additional venting for a grease trap, the inlet is the sink, and the outlet line is vented by the trap arm. The one time I did, it was a big bugger that was on the main leaving a restaurant. We vented it like an oil interceptor with a vet on each end, 2". I don't believe we were required to do so, we just did it.

I don't think grease interceptors or sediment traps serving individual fixtures require any additional venting other than the vent for the fixture it serves.

Of course I could be dead wrong.


----------



## Valconte (Mar 28, 2014)

One pipe size smaller than the inlet pipe. Air bound is 1.25 min. And anti siphon is 1.5 min. If the GI is outside of the building it's 3" min. vent size (hoar frost). Some inspectors will allow vent sizing based on trap size. This might help others but its a little late for your help now lol.


----------



## rjbphd (Feb 5, 2010)

Valconte said:


> One pipe size smaller than the inlet pipe. Air bound is 1.25 min. And anti siphon is 1.5 min. If the GI is outside of the building it's 3" min. vent size (hoar frost). Some inspectors will allow vent sizing based on trap size. This might help others but its a little late for your help now lol.


Late coming into the thread.. but early to get beat up without posting a introduction..


----------



## plumbdrum (Nov 30, 2013)

In Ma only 4" through foundation / exit building to sewer or an interceptor . The interceptor required a Chamber vent no less than 4" and the vent must enter the building and go through roof independently .

Sent from my iPhone using PlumbingZone


----------



## BC73RS (Jan 25, 2014)

Seems each code is different, here is what I found in my old 1996 BC code book, minimum 2" but three of them, one on the inlet, the tank and one on the outlet...


----------



## Plumbus (Aug 4, 2008)

The product's installation instructions should give you the sizing information you need. If not specifically addressed to your particular code requirements, a call to tech support might get a definitive answer. If that doesn't clear things up, you can always call those responsible for enforcing Ontario code in the area of your installation.


----------



## bct p&h (Jan 19, 2013)

Outlet of interceptor is half the pipe size, flow control is half the pipe size and the fixture itself is half the size.





plumbdrum said:


> In Ma only 4" through foundation / exit building to sewer or an interceptor . The interceptor required a Chamber vent no less than 4" and the vent must enter the building and go through roof independently .
> 
> Sent from my iPhone using PlumbingZone


I've had this discussion with inspectors before. Where in the code does it say the chamber vent for a grease interceptor must go through the roof separately? Every time I ask that question and they try to show it to me in the book they either can't find it or try to show me the code on sand and gas traps. 
I'm not trying to bust balls or anything but I don't see the point in a grease vent going independent. Sand and gas I completely understand buy we're talking about grease here, not flammable vapors.


----------



## plumbdrum (Nov 30, 2013)

bct p&h said:


> Outlet of interceptor is half the pipe size, flow control is half the pipe size and the fixture itself is half the size. I've had this discussion with inspectors before. Where in the code does it say the chamber vent for a grease interceptor must go through the roof separately? Every time I ask that question and they try to show it to me in the book they either can't find it or try to show me the code on sand and gas traps. I'm not trying to bust balls or anything but I don't see the point in a grease vent going independent. Sand and gas I completely understand buy we're talking about grease here, not flammable vapors.


Your correct, when I first posted that I misunderstood and thought it was a gas/oil separator., as for chamber vent of tank min is 4". Not sure if your ion Ma, if so 10.09 (3)248 CMR

Sent from my iPhone using PlumbingZone


----------



## plumbdrum (Nov 30, 2013)

I'm also talking about an outside interceptor, now that I'm rereading the first post I'm thinking he meant interior

Sent from my iPhone using PlumbingZone


----------



## bct p&h (Jan 19, 2013)

plumbdrum said:


> Your correct, when I first posted that I misunderstood and thought it was a gas/oil separator., as for chamber vent of tank min is 4". Not sure if your ion Ma, if so 10.09 (3)248 CMR
> 
> Sent from my iPhone using PlumbingZone


Live in NH but 99% of the time I work in MA.
Wasn't disagreeing about the 4" chamber vent, just the independent through the roof part. For the longest time I ran them independent because that's how I was taught to do it. That is until I was doing work at a school and one of the state inspectors informed me that I didn't have to. He said he sees it all the time and it's just a waste of time and pipe. MDC traps are a whole other ball game.


----------



## plumbdrum (Nov 30, 2013)

bct p&h said:


> Live in NH but 99% of the time I work in MA. Wasn't disagreeing about the 4" chamber vent, just the independent through the roof part. For the longest time I ran them independent because that's how I was taught to do it. That is until I was doing work at a school and one of the state inspectors informed me that I didn't have to. He said he sees it all the time and it's just a waste of time and pipe. MDC traps are a whole other ball game.


Correct

Sent from my iPhone using PlumbingZone


----------

