# Ontario Plumbing Rough-In Requirements 2026 - OBC Drain, Vent and Supply Standards

**URL:** <https://home.renovation.reviews/t/ontario-plumbing-rough-in-requirements-2026-obc-drain-vent-and-supply-standards/46953>\
**Category:** Ontario\
**Created:** [April 26, 2026, 8:02pm UTC](https://home.renovation.reviews/t/ontario-plumbing-rough-in-requirements-2026-obc-drain-vent-and-supply-standards/46953 "2026-04-26T20:02:04Z")\
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**Post date:** [April 26, 2026, 8:02pm UTC](https://home.renovation.reviews/t/ontario-plumbing-rough-in-requirements-2026-obc-drain-vent-and-supply-standards/46953/1 "2026-04-26T20:02:04Z")

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Understanding Ontario plumbing rough-in requirements prevents costly do-overs and failed inspections. This covers OBC drain/waste/vent requirements, supply sizing, and permit obligations for GTA renovation projects.

**Ontario Plumbing Code Key Requirements**

Drain slope: All horizontal drains must slope minimum 1:50 (2%). Preferred is 1:40 for drains up to 3-inch diameter.

Trap-to-vent distance: Maximum 1,350mm (4.5 ft) for 1.5-inch trap arm. 1,800mm maximum for 2-inch trap arm. Critical constraint for basement bathroom additions.

Stack sizing: 3-inch minimum for toilet connection. 4-inch stack if serving more than one toilet.

**Basement Bathroom Addition**

Adding a bathroom below the main drain exit typically requires a sewage ejector pump ($2,500-$5,000 installed). Gravity drainage is possible only if the basement floor level is above the municipal sewer connection point.

Full basement bathroom rough-in (toilet, sink, shower): $4,000-$8,000 labour plus materials. Add $3,000-$6,000 for concrete saw-cut and patch.

**Supply Pipe Materials**

PEX: Most common new installation. Flexible, freeze-resistant, $0.50-$1.50/ft. No lead concerns.  
Copper: Traditional, 50+ year lifespan, $2-$5/ft. Required in some commercial applications.

**Permit Requirements**

All new plumbing installations require a plumbing permit in Ontario. Rough-in inspection required before walls are closed. Budget $150-$400 for GTA permit fees.

Complete guide with diagrams: [Ontario Plumbing Rough-In Guide 2026 - Drain, Waste, Vent and Supply Requirements – Telegraph](https://telegra.ph/Ontario-Plumbing-Rough-In-Guide-2026---Drain-Waste-Vent-and-Supply-Requirements-04-26)