What is Polybutylene?

Heather Bailey

Polybutylene is a plastic resin used to make water pipes. Developed in the 1970s, these pipes were thought of as the pipes of the future. They were cheaper and easier to install than copper pipes. In the 1980s, however, polybutylene pipes started to fail, and many experts now recommend that these pipes be replaced in homes.

Man with a drill
Man with a drill

Polybutylene pipes were developed at the time of a building boom in the Sun Belt — the Southern portion of the United States. It's estimated that the pipes were installed in 6 million to 10 million homes in the 1980s and 1990s in the Southwestern US, as well as in the mid-Atlantic and Pacific Northwest. That's about 20 percent to 25 percent of new homes built during that time. The pipes were used both in homes and under yards to the water main. In addition to new homes, they were used in mobile homes, apartment buildings and commercial structures.

About 10 to 15 years after installation, leaks were reported in the pipes. Chlorine and other common oxidants in the public water supply reacted with the pipes and caused them to flake inside and become brittle. This led to cracks, which reduced the structural integrity of the pipes which failed, sometimes, without any warning. Even a trained eye can have a hard time spotting a bad pipe, because the flaking exists internally. Leaks, in turn, can cause great damage in a home and be expensive to repair.

Many lawsuits were filed when the pipes began leaking, claiming the manufacturing of the pipes as well as the installation were defective. A class action lawsuit in the US, Cox v. Shell, ended in a settlement with the manufacturers, though they claimed no fault. There are strict guidelines for being admitted into the class, including when the pipes were installed, the type of fittings used and what type of leak occurred.

A homeowner can look at the pipes leading to sinks, toilets and the water heater to determine if he or she has polybutylene pipes. The pipes are usually gray, though they can be blue, black or white. Polybutylene pipes in the house can be capped with copper, so seeing copper behind the toilet doesn't rule out polybutylene pipes behind the walls. Looking at the pipe that includes the main shutoff valve — usually found near the water heater — can determine whether the pipes under the yard are made of polybutylene.

Some experts recommend that property owners replace these pipes. Homes with these pipes can be difficult to insure, have higher premiums and be harder to sell. Homeowners should look for a company that specializes in polybutylene pipe replacement, rather than a general plumber. In the US, each state's plumbing licensing authority will have a list of these specialists.

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