Why it matters to the pipes
Unlike an upstairs bathroom, a basement bathroom has to drain downward into a sewer that may be only slightly lower, or even higher, than the basement floor. Its drain lines run beneath a concrete slab, which makes changing them later disruptive and costly. Getting the layout, drainage and venting right at the outset makes all the difference to how well the room works for years to come.
Have to hand
- A flashlight and a bucket
- Old towels and a pair of gloves
- The way to the main valve
Put the tools down if
- Water will not stop at the valve
- Sewage rises in a floor drain
- You smell gas near the heater
The steps, in order
- Find the main drain. Locate the main stack and the cleanout where the sewer leaves the house. Placing fixtures close to it simplifies the job.
- Check for an existing rough-in. Many Etobicoke homes have capped pipes in the floor, left by the builder for a future bathroom.
- Confirm the sewer depth. A plumber can determine whether the new fixtures sit high enough to fall to the sewer on their own or will need a pump to lift them.
- Plan the venting. Each fixture needs a vent, which usually connects to the existing stack or a new vent line.
- Choose fixtures early. Toilet rough-in distances and shower drain locations affect where the slab is cut.
- Consider flood protection. A backwater valve protects the new room from sewer backups during heavy storms.
- Get the permit. New drains in the basement typically require a building permit and inspection.
Common missteps
- Placing the shower far from the stack without accounting for drain slope under the slab.
- Skipping a backwater valve, leaving the new bathroom exposed to sewer backup.
- Forgetting ventilation. An exhaust fan vented outdoors prevents damp and mould.
- Closing in walls before the rough-in inspection is complete.
- Overlooking the water supply. An old lead or galvanized service may not deliver enough flow for an extra bathroom.
When to ring for help
Bring in a plumber at the planning stage, before framing or demolition. A drain camera inspection and a look at the water supply will tell you what the existing system can support. If the incoming service is old lead pipe, upgrading it through lead pipe replacement may be wise before adding fixtures. Spring is a popular time to start basement work; our spring plumbing checklist covers other jobs worth doing at the same time.
Thinking about the long term
A basement bathroom often becomes part of a guest suite, a teenager's space or a rental unit. Planning for that future use, with good lighting, enough hot water and a sensible location for the laundry, makes the room more valuable. Where you can, leave access panels for valves and the ejector pump so that future maintenance does not mean breaking open finished walls.
Good planning now saves money and disruption later.