Polybutylene pipe

Properties and installation[edit]

Flexibility is the material's main practical advantage: long runs can be made with few joints, and a coil can be pulled through a floor void or beneath a screed without the fittings a rigid material would need. Fewer joints in inaccessible places is a real reduction in leak risk, since concealed joints are where most avoidable failures occur.

A pipe insert is required at every push-fit joint. It supports the bore against the grip of the fitting's grab ring so the tube does not deform inwards and break the seal against the O-ring. A missing insert is among the most common causes of a slow weep on a plastic system.

Polybutylene must be protected from ultraviolet light, which degrades it, and must be kept away from direct heat sources at the boiler.

Failure modes and detection[edit]

Failures are concentrated at joints rather than in the pipe wall: insufficient insertion depth, a missing insert, a scored pipe surface giving the O-ring a leakage path, and O-ring degradation over time with heat.

Detection on polybutylene is harder than on copper for the same reasons as on other plastics. The material attenuates sound heavily, so acoustic listening and correlation are less effective, and it cannot be traced by conventional electromagnetic pipe location. Where a concealed polybutylene run is losing pressure, tracer gas is frequently the method that resolves it, and thermal imaging is used to establish the route where the circuit can be warmed. ADI Leak Detection names tracer gas and thermal imaging against the concealed pipework cases where this arises.^[4]