AAV on "S" Trap

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.

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.

Would have been cheaper and easier to do it the right way to begin with!

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 .

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. :slight_smile:

No need to use AAV in an island sink.


Brian, help in lieu of suspense to help the guy.

island venting.jpg


Nice pic Marcel,

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!

Can an AAV be used in a crawl space on a pier and beam house?

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.

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.

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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- in Appendix A.) Air Admittance Valve as a Vent Terminal

  1. Individual vents *may terminate with a connection to an *air admittance valve *as provided in Articles and (See also Sentence 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. 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

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] 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][/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]**[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=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]

Something like in attached pic perhaps; but as Marcel C mentioned, only certain brands are approved in Canada.