OBC DIVISION B · PART 9 · SECTION 9.31 — PLUMBING FACILITIES

Is a floor drain required in the basement of a house in Ontario?

Yes, generally. Where a dwelling has a basement and gravity drainage to a sewer, sump or other approved point is available, a floor drain must be installed in the basement to handle spills, condensate and minor leaks.

Code reference
A floor drain is required in the basement of a dwelling where gravity drainage can be provided to a sanitary sewer, a sump or another approved disposal location. The drain protects the lowest level from water released by leaks, appliance failures and equipment condensate, and its trap and connection details are governed by the plumbing requirements of Part 7.
OBC Division B, Subsection 9.31.6.

Paraphrased for clarity — open this provision in the BUILDAiD Library for the exact wording.

What this means in practice

The floor drain is the basement's insurance policy: water heater failures, washing machine hose bursts and furnace condensate all end up there. Slope the slab locally toward the drain and keep it near mechanical equipment where feasible. Trap seals in rarely used drains evaporate and let in sewer gas, so trap primers or periodic dosing are wise. In areas served by combined sewers, backwater valve requirements may accompany the drain. Finishing a basement over the drain, or tiling it flat, defeats the purpose and can violate the Code.

Plain language

That round grate in your basement floor is required by code. When a water heater or washing machine lets go, the drain quietly carries the water away instead of letting it flood your finished basement.

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This page is provided for general information. Building code requirements depend on your specific project, occupancy and municipality, and code editions change. Always verify requirements against the current Ontario Building Code and confirm with your local building department.