Polybutylene Pipe
Polybutylene is a gray flexible plastic supply pipe installed from the late 1970s to the mid-1990s that is prone to sudden failure and is now widely flagged by insurers and inspectors.
Polybutylene, often shortened to poly or PB, is a gray (sometimes blue or black) plastic pipe that looked like a cheap, easy answer to copper when it was installed in millions of homes between roughly 1978 and 1995. The trouble is that chlorine and other oxidants in normal tap water react with the plastic and the original fittings, making them brittle from the inside. Failures often come without warning as a fitting cracks or a line splits, which is why the material developed a reputation for surprise floods.
A homeowner usually learns they have polybutylene during a home inspection, an insurance review, or after a leak. Many insurers now refuse to write or renew a policy, or charge more, until the poly is gone, and it can complicate a sale. Because the failures are unpredictable and the material can no longer be reliably repaired piece by piece, the accepted remedy is a full repipe rather than a patch.
Polybutylene is easy to confuse with PEX at a glance since both are flexible plastic, but PEX is a different, modern, durable material and is perfectly fine. The distinguishing clues are the gray color, the old acetal or metal crimp fittings, and a stamp reading PB2110 on the pipe.
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