Polybutylene (PB) was a plastic manufactured by Shell Oil Company between 1978 and 1995 for use as piping in home plumbing systems. It was inexpensive and offered plenty of advantages over other materials, including flexibility, ease of installation and resistance to freezing. Despite its strengths, production was ceased in mid-1996 after scores of allegations surfaced claiming that polybutylene pipes were rupturing and causing property damage. In the homes that still contain this material, homeowners must either pay to have the pipes replaced or risk a potentially expensive plumbing failure.
The original piping systems were used for underground water mains and as interior water distribution piping. PB did not crack under stress or pressure; it is flexible and generally resists chemicals like oils, acids, alcohol and fats. It doesn’t corrode, doesn’t calcify and transmits a low noise. It was viewed as an excellent alternative to traditional water pipes, for both the transfer of hot and cold liquids. The creation of the polybutylene piping was an valuable choice for the housing boom, especially for lower-priced homes like mobile homes.

polybutylene pipe
How to Tell If You Have Poly

Polybutylene underground water mains are usually blue, but may be gray or black (do not confuse black poly with polyethelene pipe). It is usually 1/2" or 1" in diameter, and it may be found entering your home through the basement wall or floor, concrete slab or coming up through your crawlspace; frequently it enters the home near the water heater. Your main shutoff valve is attached to the end of the water main. If you are on city water, check the water meter at the street, near the city water main. It is wise to check at both ends of the pipe because cases have been found where copper pipe enters the home and poly pipe is at the water meter. 


Polybutylene used inside your home can be found near the water heater, running across the ceiling in unfinished basements, and coming out of the walls to feed sinks and toilets. PB pipes are usually stamped with the code “PB2110”, most commonly grey in color, 1/2" to 1" in diameter and not used for waste, drain or vent piping. In some regions of the country plumbers used copper "stub outs" where the pipe exits a wall to feed a fixture, so seeing copper here does not mean that you do not have poly.

Will the Pipes Fail?

While scientific evidence is scarce, it is believed that oxidants in the public water supplies, such as chlorine, react with the polybutylene piping and acetal fittings causing them to scale and flake and become brittle. Micro-fractures result, and the basic structural integrity of the system is reduced. Thus, the system becomes weak and may fail without warning causing damage to the building structure and personal property. It is believed that other factors may also contribute to the failure of polybutylene systems, such as improper installation, but it is virtually impossible to detect installation problems throughout an entire system.

A Class Action settlement in 1995 ensured that polybutylene water pipes were no longer acceptable by U.S. building codes. It takes about 10-15 years for polybutylene piping to deteriorate. Because it deteriorates from the inside out, it’s difficult to assess the extent of the damage. A licensed plumber can fully assess the water pipes outside and inside the home to determine the material and age of the pipes. Studies have shown that polybutylene pipes, over time, will leak and it is highly recommended that they be replaced. This type of plastic also reacts negatively to water-soluble oxidants (like chlorine) and certain disinfectants causing the pipes to deteriorate, flake and become damaged over time.
Throughout the 1980's lawsuits were filed complaining of allegedly defective manufacturing and defective installation causing hundreds of millions of dollars in damages. Although the manufacturers have never admitted that poly is defective, Shell Oil Co agreed to a $950 million Class Action settlement in 1995. An additional lawsuit was filed in 2017 to include those left out of a 1995 settlement over problems with Shell and Celanese Corp.'s polybutylene resin and acetal materials.