• Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by first logging in then clicking here: Upgrades

P3112 Island Fixture Venting

TimNY

TimNY

Platinum Member
Joined
Jan 13, 2010
Messages
1,133
Location
Charleston, SC
Looked at one of these venting a lav. Well, it's kind of like this except the vent down from the lav connects to the fixture drain from the tub, rather than downstream from the lav drain connection. Anyway, while trying to figure out the confused plumbing, I came across this from the icc: View attachment 953 WHere is the wording in the code that requires the dry vent from the island vent to the vertical stack? Is it required? Thanks,Tim

View attachment 1544

View attachment 1544

/monthly_2011_06/diagram_1.jpg.ab8da5df43d22220a597ae147958bfd3.jpg
 
Here are two easy solutions

images


FH03OCT_ISLANSI_02.JPG
 
jar546 said:
The aav cannot be used because it has to be 6" above the flood rim unlike what is shown in the photo.
Click to expand...
Check with your local codes to find out if they are legal for use in your area. And there is alternate means and methods...
 
In Mark's photo you again see the connection to the stack from the vent down from the sink.. But I don't see the wording that requires that.

I think AAV has to be 4" above the fixture arm connection, not the flood rim (I think it used to be 6" above the flood rim a code cycle or two ago)

Told him he had to provide a cleanout above the flood rim of the sink.. which is going to require an access panel.. at which point he could have used an AAV.. Doesn't really matter to me, but the plumbing below the floor is also in question.
 
Assuming a bathroom because of the tub drain connection; I’ve yet to see an island lavatory in a residential unit. Other than in commercial repair facilities with multi-station hand washing sink; island fixtures are customarily in kitchens.

P3112.1 Restricts this venting method to the island sinks and lavatories. If this is indeed an island fixture then the vent installation to the tub drain should not be possible or permitted upstream against the direction of flow.

P3112.2 This is the “foot vent” where the vent after it reaches above the drainage outlet (as opposed to the flood level rim) will eventually have to connect to the “outside vent terminal” above the highest fixture.

P3112.3 The lowest point of this vent sloped and connected in accordance Chapter 30; Sanitary Drainage shall connect to the drainage system accordingly being that this horizontal vent will need to drain as such. And because of the potential of this vent becoming clogged owing to the fact that it is a vent (not a drain that normally gets flush clear) below the flood level rim it needs to have an accessible cleanout on the vent side for “all vent piping located below the flood level rim of the fixtures.”

Question; is “highest fixture” another way of saying the highest flood level rim?
 
Last edited by a moderator:
Thanks, Francis.. P3112.2 had me confused:

"The vent or branch vent for multiple island fixture vents shall extend to a minimum of 6 inches (152 mm) above the highest island fixture being vented before connecting to the outside vent terminal."

I took is as "The vent/branch vent for multiple island fixtures..."

But what it means is, "the vent (or the branch vent, in the case of multiple fixtures), shall extend to a minimum..."

Just something I never deal with.. usually see AAVs. Probably better off, as it now seems this island vent isn't even close to compliant.

Lacking any better direction, I would say "highest fixture" means "flood rim of highest fixture", that way there is no chance of the backed up sink/lav clogging the "outside vent terminal"
 
I would say that as far as the IRC is concerned, the vent does not connect above the flood rim.

I do note that those diagrams indicate a 3" drain and vent (wow!) for the sink. Possibly an older method; maybe permissible under UPC?

Reminds me of another method I heard of.. Where the stack is 8" and there are no individual vents.
 
Tim, my understanding is for the most part a 3" horizontal will have an air space above the fluid discharge. There are allowances for bathroom and kitchen fixtures; see appendix N. I imagine given the low amount of dfu's the distance could be up to 100 ft. limited to the clean outs.
 
So where are we on this one?

I am looking through the IPC (yes I know this is an IRC issue) to see if the language is similar for AAV's.

917.4 Location. Individual and branch-type air admittancevalves shall be located a minimum of 4 inches (102 mm) above

the horizontal branch drain or fixture drain being vented.

Stack-type air admittance valves shall be located not less than 6

inches (152 mm) above the flood level rim of the highest fixture

being vented. The air admittance valve shall be located within

the maximum developed length permitted for the vent. The air

admittance valve shall be installed a minimum of 6 inches (152

mm) above insulation materials.
Click to expand...
 
There is not doubt that the photo of the AAV above is not compliant since it is neither 4" above the fixture or 6" above the flood rim.

What I would like to know is what is the actual requirement for that kitchen sink?

Can it be (AAV) 4" above the fixture drain and be compliant or does it have to be 6" above the flood rim?

I am confused by the language in that section.
 
jar546 said:
There is not doubt that the photo of the AAV above is not compliant since it is neither 4" above the fixture or 6" above the flood rim.
What I would like to know is what is the actual requirement for that kitchen sink?

Can it be (AAV) 4" above the fixture drain and be compliant or does it have to be 6" above the flood rim?
Click to expand...
Click to expand...
I am confused by the language in that section.

917.4 Location. Individual and branch-type air admittance valves shall be located a minimum of 4 inches (102 mm) above the horizontal branch drain or fixture drain being vented. The air admittance valve shall be located within the maximum developed length permitted for the vent.
Click to expand...
The fixture drain is the horizontal pipe between the trap to the vent; 906.1 & 912.2.4 The confusion may be the difference is a fixture outlet is above the fixture drain and branch drain.

The commentary notes that the air admittance valve need not extend above the flood level rim of the fixture served because in the event of a drain blockage, such device will trap air between it and the rising waste, thereby protecting the device from contamination.

Stack-type air admittance valves shall be located not less than 6 inches (152 mm) above the flood level rim of the highest fixture being vented.
Click to expand...
910.3 adding an AAV to a compliant configuration. Vent stacks as defined start 6" above the highest fixture flood level rim.

I believe confusion is explaining the difference of ground, grounded and grounding to a plumber as this is to an electrical expert.
 
That's why I always use the term "fixture arm" in relation to the AAV.. When you say "fixture drain" people just get confused.
 
That clarifies it, meaning you can have an AAV under a sink providing it extends up 4" above the fixture drain (aka horizontal pipe to the vent/aav) which must be at or above the weir of the trap anyway. Therefore it can be below the bottom of the sink if the trap is set lower.
 
That makes this installation compliant with the 4" rule since we are talking about the fixture drain and not the actual drain inside the sink.

FH03OCT_ISLANSI_02.JPG
 
You must log in or register to reply here.
Top