Polybutylene Pipe

By Frank G. Ross

Polybutylene pipe (sometimes called PB or Poly-B pipe) is a non-rigid, usually gray but at times silver or black, plastic pipe used in plumbing for drinking water supply. PB pipe is not PVC or CPVC, which is rigid white or off-white plastic pipe.  PB was introduced in the late 1970s and has been used in approximately six million mobile homes, apartments, houses and other structures in the US.  Half of the mobile homes and about 5% of the single family houses in the US are thought to employ PB for plumbing.  The product has sold under the popular trade names Qest, Thermoguard and Flex-Temp.  Polybutylene pipe is a plastic plumbing product manufactured from plastic resin supplied by Shell Oil Company.

By the late 1980s, a number of PB plumbing systems began to experience problems with leaky fittings.  Today, there are a number of class action lawsuits against the manufacturers as well as in the installers.  One of the largest (Cox v. Shell Oil Co., et al) has been settled for $950 million – the deadline for filing a claim is August 20, 1999.  As of April 1996, the Shell Chemical Co. no longer supplies polybutylene resin for pipe applications in the US.  With other class action lawsuits (Qest, Vanguard), a claim must be made within 13 years [with acetal fittings] or 16 years [with metal fittings] after the date of installation or before the year 2009, whichever comes first.

When the product first came out, acetal plastic fittings, made of a hard gray (sometimes white) plastic, were inserted into the pipe and clamped in place with an aluminum (and later a copper) band connecting the joints.  These fittings were prone to cracking and leads due to the different expansion characteristics of the plastics.  As a result, metal fittings made of copper or brass were introduced.  Although the metal fittings are more reliable, they still may suffer failures.  The tools used to crimp these connectors needed to be carefully calibrated.  Recent installations of PB piping systems use compression fittings that often have a plastic or metal nut to secure the seal.  So far, this has solved the problem of leaks at the pipe connections.

There are a number of other factors that contribute to the leaks associated with PB plumbing systems.  Although 90% of the leaks are at the joints in the piping due to poor joint connections using plastic insert fittings, 30% of the problems at the leaking joints are due to installation errors.  Another defect is the pipe itself. The pipe is usually manufactured to withstand 100 pounds per square inch and a temperature of 180° F (82° C).  One of the defects with PB pipe is the formation of stress cracks, brittle fractures due to the deformation of the tubing under stress and temperature. 

Some precautions to take if your have or are installing PB pipe:

• Do not use acetal insert fittings (use metal insert fittings or compression fittings)
• Do not use where water temperature can exceed 180° F (82° C)
• Do not use in swimming pool piping systems or where water contains more than 2 ppm of free chlorine
• Keep pipe at lest 6” (15 cm) from hot water tank, heating ducts or flue pipes
• Use metal connector at least 18” (45 cm) long at the hot water tank
• Do not use in an application where the pipe is exposed to direct sunlight
• Do not expose pipe to direct sunlight for more than 30 days during installation

If you think that you might have PB in your home of if you know you have PB in your home then having a qualified plumber evaluate your plumbing would be your best choice of action for your peace of mind.

Frank Ross is a Certified Utah Home Inspector for Pillar to Post Professional Home Inspection and a full member of the National Association of Certified Home Inspectors and a member in good standing with the Utah Better Business Bureau.  Readers may contact Mr. Ross at (435) 867-6400 or frank.ross@pillartopost.com or visit www.pillarposthomeinspection.com