Polybutylene pipe

Entry in Drain pipe and retired pipe · Updated October 29, 2026 · Written by the Know Your Pipes editors from the sources listed under References

Polybutylene pipe (PB) is a flexible gray plastic water supply pipe, joined with crimped fittings, that was introduced in US homes in the late 1970s and later became the subject of national class actions over leaks.^[1][2] A 1994 University of Arizona newsletter repeated an estimate that it had been used to plumb about six million US homes.^[2]

The material is no longer made to a current US standard. ASTM D3309, the specification for polybutylene hot- and cold-water distribution systems, was withdrawn in 2010 with no replacement.^[3]

1 Material and use

Polybutylene is a plastic made from a by-product of oil refining.^[1] A federal appeals court described Shell as the only seller of PB resin in the late 1970s, with other companies, including DuPont and Hoechst Celanese, making pipe or the raw materials for its joint fittings.^[1]

ASTM D3309 covered PB pipe, tubing and fittings for drinking-water service and distribution, rated 100 psi at 180°F, and also listed uses such as water heating, cooling and fire sprinkler piping.^[3] Builders liked PB because it was cheap and fast to install. A 1994 University of Arizona newsletter put the saving at $200 to $600 per home over CPVC or copper, and described PB as nearly the only material used in inexpensive tract houses and mobile homes.^[2]

2 Why it failed

Most trouble started at the joints. Early PB systems used insert fittings made of acetal plastic, held on with crimped bands, and an engineer studying the problem for the manufacturers reported that some acetal fitting materials lacked resistance to forms of chlorine common in public water.^[2] In laboratory work those older joints deteriorated in chlorinated water, and the engineer said the pipe itself had not yet been tested the same way.^[2]

Installation also mattered. The same report quoted a plumbing contractor saying the crimping tools needed constant calibration, because bands squeezed too tight put excess stress on the pipe.^[2] Makers blamed poor installation; homeowners and their lawyers blamed the product.^[1][2] Later systems used copper crimp bands and a manifold layout with fewer joints, though contractors in 1994 still reported leaks in those systems.^[2]

Failures tended to be sudden. In the Arizona report, plumbers described a bang, a drop in water pressure and water pouring from pipes, often damaging floors and ceilings.^[2] What to do in that moment is covered under burst pipe first steps.

3 Lawsuits and settlements

The leaks produced years of litigation, summarized in a 2003 federal appeals decision.^[1]

In Cox v. Shell Oil, filed in the Chancery Court of Obion County, Tennessee, the court approved a national settlement requiring Shell and Hoechst to contribute $950 million to replace eligible owners' leaking PB systems and repay property damage from the leaks.^[1] The separate Spencer settlement in Alabama required DuPont to pay further sums toward repair and replacement.^[1]

4 Identification and replacement

PB is usually gray, flexible and easy to cut.^[2] It can be hard to spot because the short stubs at sinks and toilets were often connected through PB-to-copper adapters, leaving copper as the only visible pipe.^[2] Looking at the supply line where it leaves the water heater, at the main shutoff, or in an unfinished basement or crawl space gives a better view; identifying your pipes covers what to look for.

Even in 1994, some insurers were cancelling or refusing coverage for homes plumbed with PB, and some Arizona cities had left it out of their plumbing codes.^[2] Replacement with PEX pipe, CPVC pipe or copper is a whole-house repipe done by a licensed plumber under permit. PB is sometimes confused with gray PEX, which joins with PEX crimp rings that look similar; the print line on the pipe settles it.