Over the years, several home building materials that were once valued for their low cost, durability, and other benefits have proved to be dangerous or unreliable. These range from asbestos, which worked well as an insulator but was also found to pose a risk of lung cancer, to aluminum wiring, an inexpensive copper alternative which is also more likely to spark a fire.

Most of these materials are found in older homes, where they remain in place long after their use was nixed in more modern buildings. But one faulty material, polybutylene, was being used in plumbing for new homes as recently as the mid-90s.

Benefits and problems

Polybutylene, a type of plastic, was once valued as a plumbing material due to its flexibility. A 1992 article in the New York Times on the advantages of plastic pipes noted how polybutylene was particularly useful in installing water-using appliances since it could be easily routed through areas that would have required demolition if rigid pipe was used.

The material had a number of other advantages as well. Nick Gromicko and Kenton Shepard, writing for the National Association of Certified Home Inspectors, say polybutylene was inexpensive, easy to install, and resistant to freezing. Anne Reagan, writing for the home improvement site Porch.com, says it could also resist corrosion and withstand more pressure and stress.

Polybutylene was most prevalent in homes built between 1978 and 1995, and was installed in millions of homes in the United States. McGarry and Madsen Home Inspection, a company in The Villages, Fla., says polybutylene was an especially popular choice for plumbing in mobile homes.

Unfortunately, polybutylene also proved to have an unforeseen weakness. Gromicko and Shepard say certain disinfectants in the water—especially chlorine used in municipal water supplies—can cause the material to flake apart. Over time, cracks in the material can eventually spread to the exterior, causing the pipe to rupture.

After many homes suffered flood damage as a result of polybutylene pipes, a class action lawsuit was filed against Shell Oil, the manufacturer of the plastic. There was some contention that the trouble was not a result of the material, but rather faulty installation causing leaks at the joints. Nevertheless, Shell agreed in 1995 to a $1 billion settlement to cover the replacement of polybutylene plumbing after a leak.

Spotting it

When checking your plumbing for polybutylene pipes, some places may be more likely to have it than others. Reagan says they are commonly found supplying water heaters, running across the basement ceiling, or feeding into sinks, toilets, or bathtubs. Exterior pipes may also be made of polybutylene, including those entering the water meter, shutoff valve, or basement walls.

Polybutylene is usually stamped with the label "PB2110." Pipes using the material are flexible and narrow, usually only a half-inch to an inch in diameter. McGarry and Madsen Home Inspection says the pipe is usually gray, although it can also be black or blue. In mobile homes, polybutylene plumbing is often visible in the cabinetry.

Copper fittings are often used on polybutylene pipes. Alan D. Gould, a home inspector writing for the New York Times in 2001, says earlier installations of polybutylene pipes had plastic couplings fitted with aluminum bands; these were the most likely to fail. Later installations switched to copper bands, and then to copper couplings as well.

Gromicko and Shepard say there are no regulations mandating the replacement of polybutylene piping, and that home inspectors are not required to note its presence. It is also difficult to test the plumbing for weaknesses, since deterioration happens from within and a home inspection will not dismantle a pipe.

Don't mistake other types of plastic plumbing for polybutylene. Some common types include PVC and polyethylene pipes.

Risks and replacement

While polybutylene can be reliable for many years, it will likely rupture after some period of time. Angie's List says some pipes will fail after only about six months, while others can last for 20 years.

Gould says leaks are most commonly found at the joints in the plumbing. Newer plumbing installations called manifold system use flexible pipe to run all the way to a supply point such as a sink, usually eliminating the use of joints and allowing easier monitoring for leaks. However, joints might still be present in hidden areas of the home where the line could not bend easily.

Even if a polybutylene pipe does not cause a catastrophic flood, it can still cause water damage that you won't be able to spot until much later. Gromicko and Shepard say a leak that occurs behind a wall or in another hidden area can go unchecked for a long time, leading to mold, deteriorating drywall, and other problems.

Polybutylene can be troublesome even if it isn't leaking. Buyers might be less likely to purchase the property, and the plumbing can also reduce the value of the home. Insurers may also increase the premiums for homeowners insurance, or even deny coverage outright.

While the settlement of the class action lawsuit provided that homeowners could have all of their polybutylene pipe replacement costs covered, claims could not be accepted unless their plumbing leaked first and this problem occurred within a certain period of time after construction. The timeframe for replacement only extended for a certain amount of time, and homeowners could only be covered under the lawsuit if they filed a claim before May 1, 2009.

Gould says polybutylene pipes cannot be repaired, but must instead be replaced. Unfortunately, this can result in several thousand dollars in expenses.