Canadian building code question

What are the building code requirements for backwater valves in Canada?

Backwater valves are typically required on building drains or sewers where fixtures are installed below the level of the upstream manhole cover or where there is a risk of sewage backup. Requirements vary by province and municipality, with some jurisdictions mandating backwater valves on all new residential construction regardless of fixture elevation.

Backwater valve requirements are one of the areas where municipal by-laws often go further than the base building code. The safest approach is to confirm the provincial plumbing code requirements first, then check whether the local municipality has additional mandatory installation rules.

What to check first

  • Check whether the building has fixtures below the level of the upstream manhole cover, as this is the primary NBC trigger for backwater valve installation.
  • Many municipalities now require backwater valves on all new residential construction regardless of fixture elevation, especially after flooding events.
  • Installation location, maintenance access, and valve type requirements vary by province and local by-law.

Jurisdiction notes

National baseline

The National Plumbing Code addresses backwater valve requirements based on fixture elevation relative to the upstream manhole. Use this as the starting framework.

Provincial plumbing code

Each province adopts the NPC with its own amendments. Some provinces have expanded backwater valve requirements beyond the national baseline.

Municipal by-laws

Many municipalities, particularly those that have experienced sewer backup flooding, have enacted by-laws requiring backwater valves on all new construction and sometimes on renovation permits.

Work through it in this order

  1. Determine whether any fixtures are below the upstream manhole cover level.
  2. Check the provincial plumbing code for backwater valve requirements applicable to the project.
  3. Verify whether the municipality has additional by-law requirements beyond the provincial code.
  4. Confirm installation location, access, and valve type requirements before specifying.

Common questions

Are backwater valves required on all new houses in Canada?

Not universally under the national code, but many municipalities now require them on all new residential construction. Check both the provincial code and local by-laws.

Where should a backwater valve be installed?

Typically on the building drain before it connects to the building sewer, in a location that provides maintenance access. Specific location requirements vary by jurisdiction.

Do backwater valves need to be accessible for maintenance?

Yes. Both the code and most by-laws require that the valve be accessible for inspection and maintenance. This affects placement decisions in the design.