Plumbing notes · renovation planning

Laying out the pipes for a lower-level washroom

A washroom downstairs adds real value to a house, and plumbing choices made early shape the whole room.

A close up of a white wall with a light shining on it — From the almanac guide on basement bathroom planning.

Begin with the drains

Find the builder stubs or the building drain. Fixtures have to sit where drains can fall properly toward the main.

Ejector or gravity

If fixtures sit lower than the sewer, an ejector lifts waste up. Many Oakville basements drain by gravity, so check before buying one.

Checklist

Permit from the Town of Oakville
Vent routing
Hot-water capacity
Backwater protection

One more thing

Fixture placement matters more downstairs than up. Toilets need a direct, short connection to the drain; showers need a trap below the slab; sinks are the most forgiving and can sit further from the main. Laying fixtures out around the drain, rather than the other way around, saves slab cutting and keeps slopes correct.

Venting is the other half of the puzzle. Each fixture must breathe through a vent, which downstairs generally means connecting to a stack already in the house or carrying a fresh one up through the floors. Air admittance valves can help in some situations where permitted, but they are not a cure-all, and the inspector will want to see a proper arrangement.

Finally, think about hot water. A basement washroom adds demand to the existing heater, and if the house already runs short of hot water on busy mornings, the new shower will make it worse. Sizing up the heater, or adding a small dedicated unit, may be part of the plan.