Canadian building code question

What are the building code requirements for plumbing venting in Canada?

Every plumbing fixture in a Canadian building must be vented to prevent trap seal loss. The National Plumbing Code establishes vent sizing based on fixture units, stack sizing, and vent terminal requirements. Provincial adoption and specific conditions like air admittance valves, wet venting, and island venting each have their own rules and limitations.

Plumbing venting is one of the most commonly questioned and misunderstood areas of the plumbing code. The rules govern vent pipe sizing, vent stack height and termination, allowable venting methods, and where alternatives like air admittance valves may or may not be used. Getting the vent system wrong can cause trap seal failures, sewer gas entry, and code violations.

What to check first

  • Every trap must be vented. The method and sizing depend on fixture count, fixture unit load, and the building's drainage system layout.
  • Vent termination height and clearance from openings are commonly missed requirements, especially on renovations and additions.
  • Air admittance valves and alternative venting methods are permitted in some jurisdictions but restricted or prohibited in others.

Jurisdiction notes

National baseline

The National Plumbing Code of Canada establishes vent sizing tables, stack requirements, vent termination rules, and alternative venting methods as the baseline framework.

Provincial plumbing code adoption

Each province adopts the NPC with amendments. Some provinces restrict air admittance valves or modify vent sizing requirements. Confirm the adopted edition.

Renovation and retrofit conditions

Existing buildings often require creative venting solutions. Check whether the jurisdiction permits alternative methods when conventional venting is not physically possible.

Work through it in this order

  1. Determine the fixture unit load and identify all fixtures requiring venting in the project.
  2. Size vent pipes using the adopted plumbing code tables for the applicable fixture unit count.
  3. Confirm vent termination height, clearance from openings, and any specific termination requirements.
  4. Check whether alternative venting methods are permitted for the specific conditions in the project.

Common questions

Can I use an air admittance valve instead of a vent pipe?

In some provinces and conditions, yes. But many jurisdictions restrict or prohibit air admittance valves, especially on new construction. Check the provincial plumbing code adoption.

How high does a plumbing vent need to extend above the roof?

Vent termination height above the roof is specified in the plumbing code and varies with climate zone and proximity to openings. It is typically not less than 150 mm but can be higher depending on conditions.

Does every fixture need its own vent?

Every fixture needs to be vented, but not necessarily with its own individual vent pipe. Wet venting, circuit venting, and other methods can serve multiple fixtures within code limitations.