Background Information

Acetal

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 (Celcon® and Delrin®) 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.

Polybutylene

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.