# Air Admittance Valves vs. Open Pipe



## JackOfAllTrades (Jan 8, 2008)

Air Admittance Valves (AAVs) like Studor eliminate the need for open pipe venting through the attic roof. It simplifies plumbing runs and cuts down on labor costs, in addition to roofing labor costs. 

Are these AAV's reliable and do they really work like the typical open pipe venting system that is commonly used? Any drawbacks?


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## TarheelTerp (Jan 6, 2009)

They aren't an either /or option for the whole house.
They are a supplement to the regular system 
and limited to the one odd small pipe situation here and there 
that can't practically be vented to the roof.


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## forresth (Feb 19, 2010)

I picked up 2 of them and ended up having to toss one. I think some PVC glue got into it while I was putting it all together. Glad I "lung tested" it before I installed it. I ended up plugging the hole and going without (just like it was before I replaced the sink).

I also wonder how long the other will last. 20 years? Should I retest annually? Just forget about it till I smell sewer gas?


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## plumberman134 (Mar 10, 2012)

JackOfAllTrades said:


> Air Admittance Valves (AAVs) like Studor eliminate the need for open pipe venting through the attic roof. It simplifies plumbing runs and cuts down on labor costs, in addition to roofing labor costs.
> 
> Are these AAV's reliable and do they really work like the typical open pipe venting system that is commonly used? Any drawbacks?


You still need at least one vent through the roof.AAVs are a 1 way vent and a plumbing vent system can't work properly with all one way vents.Yes the really work but it's a valve and like all valves they are prone to failure so at some point they are gonna need to be replaced.I do use them but not too often.2way vents through the roof will allmost never give you a problem and are worth the extra work in my opinion


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## JackOfAllTrades (Jan 8, 2008)

plumberman134 said:


> You still need at least one vent through the roof.AAVs are a 1 way vent and a plumbing vent system can't work properly with all one way vents.Yes the really work but it's a valve and like all valves they are prone to failure so at some point they are gonna need to be replaced.I do use them but not too often.2way vents through the roof will allmost never give you a problem and are worth the extra work in my opinion


Thanks for the info!

The reason why I was considering them is that the rural area the home will be in has those pack rats/Norway roof rats and they have been known to go inside of those vent tubes and wreak havoc. Also, not having to poke holes in my roof and then deal with flashing & leaks in that area is another plus. 

In my current home it of course has the roof vents and in high winds the water in the toilet will move up and down, quite a bit in really high winds. I also notice that in the summer heat (phoenix az - 115F), that the water in the toilets will evaporate fairly quickly. The home interior is at 78F with the A/C on and I wonder if the evaporation is due to plumbing vents?? 

So what I gather is that installing a roof vent is still mandatory BUT one can use these AAV's in cases where venting runs are more difficult.


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## colinp123 (May 16, 2012)

Here's what my local building code says (Ontario, Canada):

7.5.9.2. Air Admittance Valves
(1) Air admittance valves shall only be used to vent,
(a) fixtures in buildings undergoing renovation, and
(b) installations where connection to a vent may not be practical.

(2) The air admittance valves shall be located,
(a) above the flood level rim of the fixture it serves,
(b) within the maximum developed length permitted for the vent,
(c) not less than 150 mm above insulation materials, and
(d) installed in a location not subject to back pressure.

(3) Air admittance valves shall,
(a) only vent fixtures located on the same storey, and
(b) be connected to the horizontal fixture drain.

7.5.9.3. Installation Conditions
(1) Air admittance valves shall not be installed in supply or return air plenums, or in locations where they may be exposed to freezing temperatures.

(2) Air admittance valves shall be installed in accordance with the manufacturer’s installation instructions.

(3) Air admittance valves shall be rated for the size of vent pipe to which they are connected.

(4) Installed air admittance valves shall be,
(a) accessible, and
(b) located in a space that allows air to enter the valve.

(5) Every drainage system shall have one vent that terminates to open air in conformance with Sentence 7.5.6.2.(1).


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## danster44 (Sep 25, 2011)

I have a new septic system on farm land - no neighbor issues, etc. I do not want to run a wastewater vent thru the roof of my metal building,so can an exterior vent at one of the sewer line cleanouts suffice?
I rigged up a 3' vertical PVC and cut some 1/16" slots for venting with a circular saw with a CAP on top - will this serve the Ventilation purpose ( I'm using studor vents on the interior plumbing, so no wall or roof penetrations)


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## JackOfAllTrades (Jan 8, 2008)

danster44 said:


> I have a new septic system on farm land - no neighbor issues, etc. I do not want to run a wastewater vent thru the roof of my metal building,so can an exterior vent at one of the sewer line cleanouts suffice?
> I rigged up a 3' vertical PVC and cut some 1/16" slots for venting with a circular saw with a CAP on top - will this serve the Ventilation purpose ( I'm using studor vents on the interior plumbing, so no wall or roof penetrations)



What was your reasoning for NOT running any roof vents?


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## md2lgyk (Jan 6, 2009)

JackOfAllTrades said:


> What was your reasoning for NOT running any roof vents?


In my case, it was aesthetics. I have a log house with a 12/12 pitch, standing seam metal roof. I did not want to have any vent pipes showing. I was able to lay out the plumbing so that the main stack isn't visible from the front of the house. All the fixture vents tie into the main stack in the attic, so I have only the one penetration.


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## danster44 (Sep 25, 2011)

JackOfAllTrades said:


> What was your reasoning for NOT running any roof vents?


Zero roof penetrations- building is 72 x 30 and "shed roof" (single slope) and I had insulation sprayed in (open cell)

So just don't want any roof penetrations


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## colinp123 (May 16, 2012)

I'd be cautious about using one of your sewer clean out lines as a vent. What would be your clean out in this situation? Also, although I don't know too much about atmospheric pressure and what not, I believe the vent needs to be above the drain line. Obviously vent lines that exit through the roof are above the drainline, and I know for sure that when you install a AAV, its unit needs to be above the drainline.


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## colinp123 (May 16, 2012)

Danster,

I failed to realized AAV and Studor vents were the same thing. Anyway, this diagram should help (scroll down to AAV diagram):
http://www.bradyinspects.com/plumbing-vents.html

I wouldn't run the AAV from the clean out system... and remember the AAV/Studor units (as they range in price from $10-$20) usually break down and need replacing every couple of years.


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## danster44 (Sep 25, 2011)

colinp123 said:


> I'd be cautious about using one of your sewer clean out lines as a vent. What would be your clean out in this situation? Also, although I don't know too much about atmospheric pressure and what not, I believe the vent needs to be above the drain line. Obviously vent lines that exit through the roof are above the drainline, and I know for sure that when you install a AAV, its unit needs to be above the drainline.


The sewer line runs parallel (about 2' from foundation) the entire 72' side- as such, there are 3 clean out points, so I'll use only the 1st (@the high end) for venting, and the vent is removable for clean out purposes - seems to make sense.


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## JackOfAllTrades (Jan 8, 2008)

danster44 said:


> Zero roof penetrations- building is 72 x 30 and "shed roof" (single slope) and I had insulation sprayed in (open cell)
> 
> So just don't want any roof penetrations



What about bathroom exhaust fan venting? How did you bypass that?


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## md2lgyk (Jan 6, 2009)

JackOfAllTrades said:


> What about bathroom exhaust fan venting? How did you bypass that?


Probably the same way I did: exhaust the fans through the wall. The other possibility is that the bathroom(s) in this building, if there are any, don't have exhaust fans. They aren't absolutely required by code.


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## danster44 (Sep 25, 2011)

JackOfAllTrades said:


> What about bathroom exhaust fan venting? How did you bypass that?


excellent observation -- I have DC (super quiet / energy efficient) wall exhaust fans, and they currently exhaust into the attic -- I really need to run these to an outside wall vent -- need to find one I like for metal building walls that has a good insect screen on it.


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## JackOfAllTrades (Jan 8, 2008)

danster44 said:


> excellent observation -- I have DC (super quiet / energy efficient) wall exhaust fans, and they currently exhaust into the attic -- I really need to run these to an outside wall vent -- need to find one I like for metal building walls that has a good insect screen on it.


Venting into the attic is not a good idea because you are introducing humid/moist air into attic space. Ideally you want that air to exit through the roof or wall to the outside.

Like you, I don't want to have vents protruding through the roof of my home because of energy reasons and pest issues. Currently the home I am in now has bathroom vents and I get earwigs, crickets, roaches and all types of creepy crawlers that crawl in from the roof, down the vent, and into my home. I tried putting screens on the interior covers but they can still fit through the sides. 

My solution will most likely be a ERV setup which brings in outside air, filters it and then distributes it throughout the home. This can eliminate the bathroom vent issue. Other than that, one would have to find a really good screened stack that doesn't let in pests from the roof.


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## JackOfAllTrades (Jan 8, 2008)

I also found this study article online regarding AAV vs. conventional venting systems:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CEsQFjAD&url=http%3A%2F%2Fwww.ipscorp.com%2Fpdf%2Fstudor%2FStudy-AAVvsConventional_vent_cost_saving_060811.pdf&ei=bvz8UJr0BofC2wWXm4CoDA&usg=AFQjCNGO5GuH5jVibri_z2U8gRkwaHSCDQ&bvm=bv.41248874,d.b2I&cad=rja

In the end the engineers determined that AAV's were better and cost less than the conventional venting systems.


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