The Complete Bathroom Renovation Plumbing Checklist

A bathroom renovation is one of the most plumbing-intensive projects a homeowner can undertake. Getting the plumbing right from the start avoids costly corrections mid-project — and ensures your finished bathroom functions perfectly for decades.

Start by establishing your rough-in dimensions. These are the measurements from the finished wall to the centre of each drain or supply line. Standard toilet rough-in is 305mm (12 inches), but older homes sometimes have 280mm or 380mm rough-ins. Ordering fixtures before confirming these measurements is a common and expensive mistake.

Decide early whether you're moving any fixtures. Relocating a toilet, tub, or shower drain requires breaking into the subfloor and re-routing drain lines — a significant undertaking that affects your budget and timeline. If you can keep fixtures in their existing footprint, your plumbing costs drop considerably.

Discuss water pressure with your plumber. Many older homes have 45–55 PSI at the main, which is fine for standard fixtures. But a rain shower or body spray system may require a booster pump or pressure-balancing valve to perform properly.

Always install pressure-balancing or thermostatic shower valves. These prevent scalding when a toilet is flushed or another tap is turned on. Many municipalities now require them by code — but regardless of local requirements, they're simply the right choice.

Plan your ventilation before the walls go in. A properly sized exhaust fan — typically 1 CFM per square foot of bathroom area — prevents moisture buildup that leads to mould and premature deterioration of finishes. The fan must vent to the exterior, not into the attic.

Finally, schedule a pressure test before the walls are closed. Your plumber will pressurize the supply lines to confirm there are no leaks in the rough-in work. This 30-minute step can save you from opening up finished walls later — it's the most important quality check in any bathroom renovation.