Schedule an Inspection

Polybutylene Plumbing

Polybutylene plumbing (PB or PolyB) is a flexible, easy-to-cut, gray, plastic pipe with joints secured with either epoxy or insert fittings and metal crimp rings. PB was introduced in the late 1970s for use in residential plumbing. Less expensive in material cost and easier to install than traditional copper plumbing, PB has been used to pipe approximately six million homes in the U.S. However,  there is considerable concern surrounding PB’s potential to leak. Though there is no specific data to indicate an inherent problem with the pipe itself, a number of homeowners have encountered minor to severe leaks, which has led to various lawsuits against PB manufacturers in the U.S.

Associated Problems


The primary concern with PB plumbing has been the fittings, which connect the 10-foot or shorter sections of pipe. The original acetal resin-based fittings are suspected of deteriorating when exposed to chlorinated water. In addition, crimp rings, which apply pressure to the PB pipe seal the PB to the fitting, made this section of the system more susceptible to failure when the plastics deteriorated. The industry first blamed all problems on faulty installation, but lately has acknowledged that the plastic fittings have been a major problem. The original barbed insert fittings made with an acetal resin and the type of fitting and crimp rings used have undergone numerous changes. The original aluminum crimp rings were changed to copper; the crimping tool was redesigned several times; and the acetal fittings were replaced with the copper and brass fittings that are still in use today.

Though the primary focus of the debate has revolved around the fittings, PB pipes have also undergone modification to produce a stronger, more durable product. Premature deterioration and failure of the pipe has occurred.

There are many theories on the cause of the premature deterioration and failure of the pipe. One theory is that when the piping is stored outdoors for a period of time or exposed to sunlight after installation, ultraviolet (UV) radiation from sunlight adversely alters the chemistry of the plastic, causing deterioration. The second theory for the premature deterioration and failure of the pipe is a reaction to oxidants (e.g. chlorine) in the drinking water. However, no studies or information can support those theories at this time. The manufacturers, even today, continue to maintain that the failures with the PB tubing are due to installation errors and/or misuse rather than product failure.

Heating Systems
A secondary concern involves the use of PB pipe for hot water heating systems. The pipe allowed the oxygen to penetrate the pipe and oxygenate the water. The additional oxygen in the re-circulated water was suspected of causing the premature rusting and deterioration of the internal components of the heating unit, including the boiler, heat exchanger and water pump. The PB pipe has since been modified with a coat to prevent oxygen from penetrating the pipe walls.

Identifying Polybutylene Plumbing

How to identify
Polybutylene (PB) plumbing, when used for the potable water supply system in the house, is a gray, (possibly silver or black) plastic pipe. Since the pipe is used with copper stab-outs for fixtures with exposed plumbing (such as in the bathroom), it is necessary to look in an area where the main water supply plumbing is exposed, such as in an unfinished basement, crawlspace or under the kitchen sink. Note: PB for underground service from the water company to a structure or “Yard Service Line” is blue (possibly gray or black). Yard Service is not readily visible. PB pipe is not used for drains, waste or vent piping.

The condition of the PB pipe and fitting cannot be determined by any inspection method since there are no visible signs of deterioration until failure occurs.

What to do?

There is no single course of action that is recommended for consumers with a PB system. Many recommend replacing the entire system, even if there have not been any problems. This course of action should be considered on an individual basis, taking into account a person’s level of risk aversion, the types of materials used and the age of the system, as well as past performance. For information on the Cox v Shell settlement contact the Consumer Plumbing Recovery Center at (800) 356-3496 or visiting their Web site at

Background Information

In the late 1960s, Hoechst Celanese Corporation (HCC) and the DuPont Corporation developed a polymer acetal (polyoxymethylene) resin that could be used in the manufacturing of plastic products. Acetal resin provides plastics with certain qualities such as stiffness and resistance to heat, wear and solvents. The commercial names of the acetal resin are Celcon (HCC) and Delrin (DuPont), which are widely used in the plastics industry.

Acetal resin was later used to manufacture the plastic fitting first used with polybutylene piping. However, later studies revealed that plastics containing the resin deteriorate when exposed to chlorine or chlorinated water. Steven Reiber, of HDR Engineering, states in his study Chloramines Effects on Distribution System Materials (September 1993), “The thermoplastics portion of the study demonstrated that the two acetal polymers (CelconŽ and DelrinŽ) are susceptible to both free and combined chlorine attack.” In addition, Reiber states, “There’s been some evidence that the acetal polymers that have been used to form some of the joint materials used with the plastic pipe, have a lack of resistance to some of the chlorine species common in distribution water systems.”

Reiber found that “some forms of oxidants [e.g., chlorine] are more adverse than others and cause exfoliation that weakens the structure. Because [the joints] are under tension, it causes a leak.”

The use of polymer acetal fittings were replaced by the use of copper or brass fittings.

The primary manufacturer of Polybutylene (PB) is the Shell Corporation, which began production and sale of PB piping in 1977 and 1978. Shell later bought the exclusive manufacturing right from Witco Chemical in 1986. Less expensive than traditional copper pipe and easier to install, PB flourishes in the U.S. and abroad.

However, as early as the 1980s, leaking problems with the PB system arose. The primary cause of the leaks was assumed to be related to the acetal fittings. However, manufacturers of raw PB, including Shell Oil, Hoechst Celanese Corporation and Dupont De Nemours, blame the bulk of leaks and ruptures on improper installation. PB manufacturer spokesperson Carrie Chassin says, “The main problem has been at the joints. Some plumbers just took old brass fittings and used them for plastic — that’s one piece of the puzzle.” Chassin says the makers of PB piping have corrected problems with leaks.

However, with the continued rising concern with PB, Shell, HCC and DuPont formed the Consumer Plumbing Recovery Center in 1991 to deal with customer complaints. The Center was later used to handle the claims resulting from class action lawsuits brought against the manufacturers. The largest of the class action suits and one of the largest suits in U.S. history is the Cox v Shell settlement of $950 million in 1995.

PB piping remains popular among many home builders because it offers savings of $200 to $600 per home compared to CPVC and copper piping. PB piping is almost the exclusive material used for plumbing in inexpensive tract houses and mobile homes. The piping itself is about half the cost of copper, but more expensive than CPVC. Major cost savings come from lower installation costs by using semi-skilled labor.


As Described in the Cox v. Shell Settlement:

Polybutylene plumbing inside a structure (“PB In-House Plumbing”) is a potable water supply system containing polybutylene (“PB”) pipe and either acetal (plastic) or metal insert fittings (such as tees, and elbows). PB pipe is a non-rigid, sometimes curved, usually gray (or possibly silver or black) plastic pipe. When used in the underground service from the water company to a structure (a “Yard Service Line”), PB pipe is blue, gray or black. PB pipe is not used for drains, waste or vent piping. Also, PB pipe is not PVC or CPVC, which is a rigid white or off-white plastic pipe. “PB Plumbing” refers to both PB In-House Plumbing and Yard Service Line.

Insert fittings are used to join pieces of polybutylene pipe. The insert fitting is inserted into the pipe and clamped with a metal (aluminum or copper) crimp ring over the outside of the pipe. Metal insert fittings are either copper or brass. Acetal insert fittings are hard gray or white plastic. They are not black. Insert fittings are not grabber, flare or compression fittings, which are often threaded and use a plastic or metal nut to secure the seal.