Testing of PEX Plumbing Shows It Is Failure Prone

*George Fleming
Fleming, Nolen & Jez, L.L.P.
2800 Post Oak Blvd., Suite 4000
Houston, TX 77056-6109

PEX Plumbing Systems are in millions of homes in the United States. Our testing shows that PEX plumbing pipe is subject to stress corrosion cracking which leads to failure. These failures can cause significant damage to homes that contain the PEX plumbing systems.

PEX (or cross-linked polyethylene) is part of a potable water supply system that is touted as having a number of advantages over metal pipe (copper, iron, or lead) or rigid plastic pipe (PVC, CPVC, ABS) systems. The suppliers of PEX plumbing systems advertise them as flexible, resistant to scale and chlorine, that they don’t corrode or develop pin holes, that they are faster to install than metal or rigid plastic; and that they have fewer connections and fittings.

Our testing shows that the resin used for PEX plumbing systems is subject to cracking from the inside out, which lead to leaks. This is due to the reaction of the PEX material to this small amount of chlorine that is in the U.S. potable water supply, combined with stress.

The following is a failure site on a piece of PEX tubing as seen by a lower power optical microscope on the inner surface of the pipe:

PEX pipe cracks

The above shows the micro cracks to have coalesced into a more or less continuous crack.

Scanning electron microscope images were taken at higher magnifications at samples of PEX pipe:

PEX cracks

The above shows the sectioning of the PEX tubing along the micro cracks’ direction in order to investigate the failure mechanism. The initiation point of the leak propagated from the inner surface to the outer surface. This is at the point where the potable chlorinated water washes away the PEX stabilizer and crack initiation occurs from the inside out as a result of chlorine corrosion.

Micro cracks starting at the inner surface and leading to the outer surface of PEX tubing result in water leakages to the outside.

tube inner diameter

Notice how the micro cracks extend downward toward the outer surface of the pipe. The white lines shown at higher magnification indicate the initiation and progression of stress corrosion cracking caused by the inability of the PEX material to withstand corrosion from the small amount of chlorine in the potable water supply.

Other locations show the cracking occurring at higher magnifications as shown below:

other crack locations

And other testing under higher magnification of cross sections clearly show formation of many micro cracks emanating from the inner surface towards the outer wall as shown below:

inner diameter

The evidence this law firm has uncovered is based on our testing which strongly points to the oxidation of PEX starting from the inner surface which was in contact with potable water containing chlorine or chlorine disinfectants. Oxidized PEX areas then become initiation sites for micro cracks in the inner surface of PEX. On further oxidation, these micro cracks propagate outward until the cracks breach the outer surface of PEX, thereby creating water leakage and failure of the PEX tubing. These water leaks can occur behind the walls and in the attics of homes, causing significant damage.

*George Fleming is a trial lawyer with the law firm of Fleming, Nolen & Jez, L.L.P. He previously represented over 60,000 individual homeowners in the polybutylene plumbing system litigation. After Fleming tried the case 8 times to a successful jury verdict, the case was settled resulting in a replumb of almost 6 million homes.
Categories: Product Liability