Polybutylene, usually called poly B, is a flexible grey plastic supply pipe installed in homes across British Columbia and Alberta from the late 1970s until the mid 1990s. It was cheap, quick to install and widely approved at the time. The problem is internal: chlorine and other oxidants in treated water slowly break down the pipe wall from the inside, and the damage is not visible from the outside.
Where poly B is found
Water service entry
Where the supply enters the home, usually near the main shutoff. This is often the easiest place to confirm what the house is piped with.
Hot water tank
The supply and outlet connections at the tank are usually exposed, and heat accelerates the breakdown of the pipe.
Under sinks and toilets
Short stubs are often visible behind vanities and at toilet supply valves, even when the rest of the system is hidden.
Basement ceilings
Unfinished basements show long runs between the joists, which is the clearest view of how much pipe is in the house.
Mechanical rooms
Manifolds and distribution points are usually grouped in the utility room, where several lines branch off at once.
Inside walls and ceilings
Most of the system runs out of sight. A leak here can release a lot of water before anyone notices it.
Fittings and crimp rings
Grey plastic acetal fittings have a worse failure record than metal ones. Fittings and rings are worth checking even when the pipe itself looks sound.
Underground service line
Blue poly B was used for buried supply lines between the street and the house on some properties.
The risks
Poly B degrades from the inside out, so failures tend to arrive without warning. The common consequences are:
- Sudden pipe failure and flooding
- Cracked acetal fittings at joints
- Brittleness and micro-fractures from chlorine exposure
- Repeat leaks in different parts of the same system
- Higher premiums, or an insurer declining coverage
The insurance question is often the one that matters most in a purchase. Coverage varies between providers, and some will not write a policy on a home that still has its original poly B. Because the whole system aged under the same conditions, a single leak is usually a sign of wider deterioration rather than an isolated fault, which is why a repair frequently leads to a full re-pipe within a few years.
Confirm insurance before you remove conditions. Poly B is not banned and does not have to be replaced immediately, but it changes what a home costs to insure and maintain. Have a home inspector confirm what the house is piped with, then speak to an insurer before the condition period ends rather than after.