Our Ajax home has polybutylene plumbing — should we replace all the bathroom supply lines during a complete reno or just the visible ones?

Replace all of it — not just the visible sections. Polybutylene plumbing is a known failure risk, and a complete bathroom renovation is the single best opportunity you will ever have to eliminate it entirely from your supply system while walls are already open and trades are already on site.

Polybutylene (PB) pipe — identifiable by its grey, blue, or black flexible plastic and typically stamped "PB2110" — was installed widely across Ontario from the late 1970s through the mid-1990s. Ajax and the broader Durham Region saw enormous residential growth during exactly that window, which means PB is extremely common in the housing stock there. The pipe itself degrades from the inside out when exposed to chlorinated municipal water, which is what every Ajax home receives from the Region of Durham's water system. The chlorine oxidizes the inner wall of the pipe, causing it to become brittle and develop micro-fractures over time. The fittings — particularly the acetal plastic push-fit connectors — are often the first point of failure. The problem is that you cannot see this internal degradation from the outside. A pipe that looks perfectly intact can fail without warning.

Replacing only the visible supply lines in your bathroom leaves the hidden runs — inside walls, under floors, and through the ceiling of any space below — still in service. Those sections are under the same constant water pressure and experiencing the same chlorine exposure as the lines you replaced. You will have spent money on a partial fix while leaving the highest-risk sections (the ones you cannot monitor) untouched. If a hidden PB line fails after your renovation is complete, you are looking at tearing out brand-new tile, a new vanity, and freshly finished walls to access the damage. The cost of that scenario dwarfs the cost of doing a complete replacement now.

The practical case for doing it all during the reno is straightforward. Your plumber is already there. Walls are already open. Demolition costs are already paid. The incremental cost of replacing the full bathroom supply system — both hot and cold runs from the nearest accessible manifold or main — while you have access is a fraction of what it would cost as a standalone project. Your plumber can run new PEX-A (the crosslinked polyethylene that has become the standard replacement material across the GTA) through the same pathways the PB currently occupies. PEX-A is flexible, freeze-resistant, chlorine-resistant, and carries a long service life. It is also what most Durham Region plumbers are most comfortable working with, and it is code-compliant under the Ontario Plumbing Code.

A few practical points worth knowing. First, confirm with your plumber whether the PB extends beyond the bathroom — if it is your main supply system throughout the house, a full house repipe is worth discussing while you have the momentum and a licensed plumber already engaged. Second, make sure your plumber pulls the required plumbing permit through the City of Ajax Building Services for any supply line modifications — this is not optional, and the inspection protects you. Third, verify your contractor carries WSIB coverage and adequate liability insurance before work begins.

If you are already investing $25,000–$35,000 in a mid-range bathroom renovation, the cost of a complete supply line replacement in that bathroom — typically $800–$2,500 depending on run lengths and access — is a small fraction of the total project budget and one of the highest-value decisions you can make for the long-term integrity of your home.

Toronto Bath Remodeling can match you with licensed plumbers and bathroom renovation contractors in the Ajax area through the Toronto Construction Network. Browse local professionals at torontoconstructionnetwork.com/directory?category=bathroom-renovations or get matched for free through Toronto Bath Remodeling.