# AAV on "S" Trap **URL:** \ **Category:** Plumbing Inspections\ **Created:** [February 6, 2011, 2:28am UTC](https://forum.nachi.org/t/aav-on-s-trap/56380 "2011-02-06T02:28:48Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![kblair1](https://avatars.discourse-cdn.com/v4/letter/k/7ba0ec/32.png) [@kblair1](https://forum.nachi.org/u/kblair1)\ **Post date:** [February 6, 2011, 2:28am UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/1 "2011-02-06T02:28:48Z")
Are AAV’s allowed with S traps. In this installation the AAV does not have the minimum 4" clearance above the crown of the trap but I was just wondering if they are allowed on S traps in most areas. ![P2030139.JPG](https://global.discourse-cdn.com/internachi/original/3X/0/2/022448a9fc613d7cf9d416566f14c6da7297b9f7.jpeg) ---
**Author:** ![Brian\_A.MacNeish](https://avatars.discourse-cdn.com/v4/letter/b/90db22/32.png) [@Brian\_A.MacNeish](https://forum.nachi.org/u/Brian_A.MacNeish)\ **Post date:** [February 6, 2011, 4:13am UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/2 "2011-02-06T04:13:35Z")
> [@kblair1](#): > > Are AAV’s allowed with S traps. In this installation the AAV does not have the minimum 4" clearance above the crown of the trap but I was just wondering if they are allowed on S traps in most areas. Not allowed in Canada unless by some local inspectors. ---
**Author:** ![jpope](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/jpope/32/59425_2.png) [@jpope](https://forum.nachi.org/u/jpope)\ **Post date:** [February 6, 2011, 5:48pm UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/3 "2011-02-06T17:48:17Z")
The question should be - “are AAV’s allowed” - period. The S-trap is wrong, regardless of the vent system used. Many jurisdictions do not allow AAV’s, so you’ll have to check with your AHJ. If so, then it should be at a higher elevation under the sink. That whole drain line configuration is a mess, I’d defer the entire thing for correction. ---
**Author:** ![jjonas](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/jjonas/32/301755_2.png) [@jjonas](https://forum.nachi.org/u/jjonas)\ **Post date:** [February 6, 2011, 6:08pm UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/4 "2011-02-06T18:08:40Z")
Would have been cheaper and easier to do it the right way to begin with! ---
**Author:** ![agallatin](https://avatars.discourse-cdn.com/v4/letter/a/91b2a8/32.png) [@agallatin](https://forum.nachi.org/u/agallatin)\ **Post date:** [February 7, 2011, 12:17am UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/5 "2011-02-07T00:17:33Z")
AAVs are allowed here but only in applications where stacks aren’t possible . Such as a sink in a kitchen island , that would be the most likely . Yes the job in the pics is a mess . ---
**Author:** ![mcyr](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/mcyr/32/173319_2.png) [@mcyr](https://forum.nachi.org/u/mcyr)\ **Post date:** [February 7, 2011, 1:25am UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/6 "2011-02-07T01:25:10Z")
Jeff is right, the s-trap is illegal and the studor vent is only allowed in certain areas. Here in Maine this whole abortion is illegal. 🙂 ---
**Author:** ![Brian\_A.MacNeish](https://avatars.discourse-cdn.com/v4/letter/b/90db22/32.png) [@Brian\_A.MacNeish](https://forum.nachi.org/u/Brian_A.MacNeish)\ **Post date:** [February 7, 2011, 3:44am UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/7 "2011-02-07T03:44:31Z")
> [@agallatin](#): > > AAVs are allowed here but only in applications where stacks aren’t possible . Such as a sink in a kitchen island , that would be the most likely . Yes the job in the pics is a mess . No need to use AAV in an island sink. [http://www.familyhandyman.com/DIY-Projects/Plumbing/Kitchen-Plumbing/how-to-plumb-an-island-sink](http://www.familyhandyman.com/DIY-Projects/Plumbing/Kitchen-Plumbing/how-to-plumb-an-island-sink) ---
**Author:** ![mcyr](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/mcyr/32/173319_2.png) [@mcyr](https://forum.nachi.org/u/mcyr)\ **Post date:** [February 7, 2011, 10:28pm UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/8 "2011-02-07T22:28:10Z")
Brian, help in lieu of suspense to help the guy. ![island venting.jpg](https://global.discourse-cdn.com/internachi/original/2X/d/d430406c235d1a45e5ed9577e7907b783bcc4a4c.jpeg) 🙂 ---
**Author:** ![jszczesny](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/jszczesny/32/229323_2.png) [@jszczesny](https://forum.nachi.org/u/jszczesny)\ **Post date:** [February 8, 2011, 3:11am UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/9 "2011-02-08T03:11:16Z")
Nice pic Marcel, ---
**Author:** ![Brian\_A.MacNeish](https://avatars.discourse-cdn.com/v4/letter/b/90db22/32.png) [@Brian\_A.MacNeish](https://forum.nachi.org/u/Brian_A.MacNeish)\ **Post date:** [February 8, 2011, 3:47am UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/10 "2011-02-08T03:47:27Z")
> [@mcyr](#): > > Brian, help in lieu of suspense to help the guy. > > ![island venting.jpg](https://global.discourse-cdn.com/internachi/original/2X/d/d430406c235d1a45e5ed9577e7907b783bcc4a4c.jpeg) > > 🙂 Didn’t the picture from the article come through on your system? If it did then I don’t understand your comment. When you get into the article the picture actually blows up very well! ---
**Author:** ![gmohel](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/gmohel/32/170992_2.png) [@gmohel](https://forum.nachi.org/u/gmohel)\ **Post date:** [February 21, 2011, 1:42pm UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/11 "2011-02-21T13:42:15Z")
Can an AAV be used in a crawl space on a pier and beam house? ---
**Author:** ![Dustin\_Racine](https://avatars.discourse-cdn.com/v4/letter/d/ba9def/32.png) [@Dustin\_Racine](https://forum.nachi.org/u/Dustin_Racine)\ **Post date:** [March 6, 2011, 7:18am UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/12 "2011-03-06T07:18:30Z")
here (alberta) u can only use aav’s or “cheater vents” 1)on a island, 2)where theres a serious chance of freeze up on a vent terminating to open air or 3) where installing a true vent is not practible (assuming if u had to start opening walls to tie vent in above “flood level rim” of fixture on above floor). Not word for word out of the code, but thats my interpretation.Also, cheater vents should be piped as high as possible under cabinets for best results, “T” fittings are not allowed in drainage applications, and as u said there’s also a “s-trap” That drain should be ripped out and redone. ---
**Author:** ![jallingham](https://avatars.discourse-cdn.com/v4/letter/j/53a042/32.png) [@jallingham](https://forum.nachi.org/u/jallingham)\ **Post date:** [March 9, 2011, 11:37pm UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/13 "2011-03-09T23:37:26Z")
> [@Brian\_A.MacNeish](#): > > Not allowed in Canada unless by some local inspectors. Brian What province are you in. It’s my understanding that they are allowed in Ontario…saw our friend Mike Holmes install one on one of his shows. ---
**Author:** ![mcyr](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/mcyr/32/173319_2.png) [@mcyr](https://forum.nachi.org/u/mcyr)\ **Post date:** [March 9, 2011, 11:43pm UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/14 "2011-03-09T23:43:39Z")
**Occupation: Plumber** **Years Experience: since '89 as a journeyman** **Location: Rankin Inlet, Nunavut, Canada** Join Date: Sep 2008 Posts: 1,468 Nominated 21 Times in 11 Posts > **[InterNACHI®️ Forum](https://forum.nachi.org/)** > > The InterNACHI®️ forum is a place for home inspectors and InterNACHI®️ members to discuss everything and anything related to the home inspection industry. Thread of the Week Award(s): 3 i can’t speak for the ontario code but while it hasn’t been approved for use in canada, stores are allowed to sell them. as long as it is installed as close as possible to the trap, accessible, and as high as possible for the fixture it serves (ie; under the counter), you shouldn’t have any problems. if it’s installed properly, when the water is discharged or drained from the fixture you should be able to hear it sucking in air. Another post says; They are legal in Canada, but with restrictions. The main one being the vent must be of the “approved type” ie. Studor AAV, Oatey SureVent, etc. Section 2.5.9 of the National Plumbing Code of Canada covers this. Here’s the entry from the code book (I love my scanner!) 2.5.9. Air Admittance Valves (See A-2.2.10.16.(1) in Appendix A.) 2.5.9.1. Air Admittance Valve as a Vent Terminal \* 1. Individual vents \*may terminate with a connection to an \*air admittance valve \*as provided in Articles 2.5.9.2. and 2.5.9.3. (See also Sentence 2.2.10.16.(1).) 2.5.9.2. Air Admittance Valves \* 1. Air admittance valves \*shall only be used to vent \*a)\*\*fixtures \*located in island counters, \*b)\*\*fixtures \*that may be affected by frost closure of the vent due to local climatic conditions, \*c)\*\*fixtures \*in one- and two-family dwellings undergoing renovation, or d)installations where connection to a vent may not be practical. 2. \*Air admittance valves \*shall be located a)not less than 100 mm above the horizontal \*branch \*drain or \*fixture drain \*being vented, b)within the maximum \*developed length \*permitted for the vent, and c)not less than 150 mm above insulation materials. 2.5.9.3. 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 the outdoors in conformance with Sentence 2.5.6.2.(1). ---
**Author:** ![jallingham](https://avatars.discourse-cdn.com/v4/letter/j/53a042/32.png) [@jallingham](https://forum.nachi.org/u/jallingham)\ **Post date:** [March 10, 2011, 12:03am UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/15 "2011-03-10T00:03:01Z")
Looks like they have to be installed in the horizontal part of the drain also, pretty much eliminating them from use on an S-trap. **[size=2]7.5.9.2. Air Admittance Valves[/size]** \*\*size=2 \*\* [/size]_[size=2]Air admittance valves [/size]_[FONT=TimesNewRomanPSMT][size=2][FONT=Times New Roman]shall only be used to vent,[/FONT][/size][/FONT][FONT=TimesNewRomanPSMT] size=2 [/size][/FONT]_[FONT=Times New Roman][size=2]fixtures [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]in [/size][/FONT]_[FONT=Times New Roman][size=2]buildings [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]undergoing renovation, and[/size][/FONT] [size=2]FONT=TimesNewRomanPSMT installations where connection to a [/size][/FONT]_[FONT=Times New Roman][size=2]vent [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]may not be practical.[/size][/FONT] \*\*size=2 [/size]\*\*[size=2]The [/size]_[size=2]air admittance valves [/size]_[FONT=TimesNewRomanPSMT][size=2][FONT=Times New Roman]shall be located,[/FONT][/size][/FONT][FONT=TimesNewRomanPSMT] size=2 above the [/size][/FONT]_[FONT=Times New Roman][size=2]flood level rim [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]of the [/size][/FONT]_[FONT=Times New Roman][size=2]fixture [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]it serves,[/size][/FONT] [size=2]FONT=TimesNewRomanPSMT within the maximum [/size][/FONT]_[FONT=Times New Roman][size=2]developed length [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]permitted for the [/size][/FONT]_[FONT=Times New Roman][size=2]vent[/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2],[/size][/FONT] [size=2]FONT=TimesNewRomanPSMT not less than 150 mm above insulation materials, and (d) installed in a location not subject to back pressure. [/size][/FONT]\*\*size=2 [/size]\*\*[FONT=TimesNewRomanPSMT][size=2][FONT=Times New Roman]Air admittance valves shall,[/FONT][/size][/FONT][FONT=TimesNewRomanPSMT] size=2 only vent [/size][/FONT]_[FONT=Times New Roman][size=2]fixtures [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]located on the same [/size][/FONT]_[FONT=Times New Roman][size=2]storey[/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2], and[/size][/FONT] [size=2]FONT=TimesNewRomanPSMT be connected to the horizontal [/size][/FONT]_[FONT=Times New Roman][size=2]fixture drain[/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2].[/size][/FONT] ---
**Author:** ![mgratton](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/mgratton/32/58251_2.png) [@mgratton](https://forum.nachi.org/u/mgratton)\ **Post date:** [March 10, 2011, 12:21am UTC](https://forum.nachi.org/t/aav-on-s-trap/56380/16 "2011-03-10T00:21:56Z")
> [@jallingham](#): > > Looks like they have to be installed in the horizontal part of the drain also, pretty much eliminating them from use on an S-trap. > > **[size=2]7.5.9.2. Air Admittance Valves[/size]** > > \*\*size=2 \*\* > [/size]_[size=2]Air admittance valves [/size]_[FONT=TimesNewRomanPSMT][size=2][FONT=Times New Roman]shall only be used to vent,[/FONT][/size][/FONT] > > [FONT=TimesNewRomanPSMT]size=2 [/size][/FONT] > > _[FONT=Times New Roman][size=2]fixtures [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]in [/size][/FONT]_[FONT=Times New Roman][size=2]buildings [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]undergoing renovation, and[/size][/FONT] > > [size=2]FONT=TimesNewRomanPSMT installations where connection to a [/FONT][/size] > > _[FONT=Times New Roman][size=2]vent [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]may not be practical.[/size][/FONT] > > **size=2 [/size]** > > [size=2]The [/size]_[size=2]air admittance valves [/size]_[FONT=TimesNewRomanPSMT][size=2][FONT=Times New Roman]shall be located,[/FONT][/size][/FONT] > > [FONT=TimesNewRomanPSMT]size=2 above the [/size][/FONT] > > _[FONT=Times New Roman][size=2]flood level rim [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]of the [/size][/FONT]_[FONT=Times New Roman][size=2]fixture [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]it serves,[/size][/FONT] > > [size=2]FONT=TimesNewRomanPSMT within the maximum [/FONT][/size] > > _[FONT=Times New Roman][size=2]developed length [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]permitted for the [/size][/FONT]_[FONT=Times New Roman][size=2]vent[/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2],[/size][/FONT] > > [size=2]FONT=TimesNewRomanPSMT not less than 150 mm above insulation materials, and[/FONT][/size] > > [size=2]FONT=TimesNewRomanPSMT installed in a location not subject to back pressure. > > [/FONT][/size]**size=2 [/size]** > > [FONT=TimesNewRomanPSMT][size=2][FONT=Times New Roman]Air admittance valves shall,[/FONT][/size][/FONT] > > [FONT=TimesNewRomanPSMT]size=2 only vent [/size][/FONT] > > _[FONT=Times New Roman][size=2]fixtures [/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2]located on the same [/size][/FONT]_[FONT=Times New Roman][size=2]storey[/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2], and[/size][/FONT] > > [size=2]FONT=TimesNewRomanPSMT be connected to the horizontal [/FONT][/size] > > _[FONT=Times New Roman][size=2]fixture drain[/size][/FONT]_[FONT=TimesNewRomanPSMT][size=2].[/size][/FONT] Something like in attached pic perhaps; but as Marcel C mentioned, only certain brands are approved in Canada. ![1659.jpg](https://global.discourse-cdn.com/internachi/original/3X/8/7/87f9c334bbbf6ed0332820dbdecaa1c8eb64cb03.jpeg)