How is an Ottawa bathroom laid out around one stack?

Great question about plumbing layout. In Ottawa homes — especially older ones in neighbourhoods like Glebe, Westboro, or Centretown — bathrooms are almost always designed around a single main soil stack, which is the large vertical drain pipe that runs from the basement to the roof.

The stack is the anchor point for everything. Your toilet, sink, and tub or shower all drain into this one pipe. To keep costs down and plumbing code-compliant, fixtures are positioned as close to the stack as possible, minimizing the length of horizontal drain runs.

Toilet placement comes first because it has the largest drain (typically a 3" or 4" pipe) and the strictest slope requirements. The toilet is usually positioned directly adjacent to the stack, or connected with a very short horizontal run. In Ontario, drain pipes must slope at approximately 1/4" per foot toward the stack to ensure proper drainage — your contractor will confirm exact OBC requirements for your specific situation.

The tub or shower is typically on the same wall as the stack, or on an adjacent wall within a short run. Tub drains connect via a 1.5" or 2" pipe. The sink is the most flexible fixture and can be positioned a bit further away since its drain is smaller and carries less volume.

Wet wall placement matters a lot in Ottawa renovations. The "wet wall" — the thicker wall that houses the stack and supply lines — is usually 6" wide rather than the standard 4", giving room for the 3–4" stack pipe. When Ottawa Bathrooms plans a renovation, we work around this existing infrastructure whenever possible, because moving the stack significantly increases project cost and almost always requires a permit.

For basement bathrooms, the stack situation changes — you're typically adding an ejector pump or tying into the main drain below the slab, which requires both a plumbing permit and a building permit through the City of Ottawa.

If you're planning a renovation and wondering whether your layout needs to change, a quick site visit makes all the difference. Ottawa Bathrooms offers free consultations — we can assess your existing stack location and design the most efficient layout for your space.