Polybutylene (Poly-B) plumbing
Grey plastic supply piping that micro-fractures when exposed to chlorinated municipal water, presenting extreme burst risk.
Popular 1978–1997 (peak 1993); removed from the National Plumbing Code in 2005.
What it means for you: Standard unit-owner policies often exclude or place high deductibles on Poly-B water damage.
Cost signal: Failure rate ~95% within 10–15 years; repipe cost per unit is significant.
Check: Grey flexible plastic pipe at the manifold/fixtures; repipe certificate.