Is an AAV allowed under the Ontario plumbing code?

AAVs (Air Admittance Valves) are permitted under the Ontario Building Code, but with specific conditions and limitations that are important to understand before installation.

The OBC does allow AAVs as an alternative to traditional open-air venting in certain situations. They must be a CSA-certified device (meeting CSA B125.3 or equivalent standards), and they cannot be used as a wholesale replacement for your home's main vent stack. The primary vent stack must still terminate to open air — AAVs are intended to supplement the venting system, not replace it entirely.

Where AAVs are commonly permitted is for individual fixture venting in situations where running a traditional vent through the roof is impractical — for example, a kitchen island sink, a basement bathroom addition, or a fixture added during a renovation. They must be installed in an accessible location, above the fixture's flood level rim, and in a space that has adequate air supply (not a completely sealed cavity).

Ottawa-specific context: Even though the OBC permits AAVs, your local building inspector has some discretion in interpretation, and permit requirements still apply. Ottawa Building Services may have specific expectations about where and how AAVs are used. City of Ottawa requirements may vary — confirm with your licensed plumber before proceeding, and verify with Ottawa Building Services if you're pulling your own permit.

The key safety consideration is that AAVs are mechanical devices that can fail over time. A failed AAV can allow sewer gases — including hydrogen sulfide and methane — into your home. Traditional open venting doesn't have this failure mode, which is why many plumbers prefer it where feasible.

If you're planning a fixture addition or renovation and wondering whether an AAV is the right call for your specific situation, Ottawa Pro Plumbing can assess your existing venting system and recommend the best approach. Feel free to request a free consultation.