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Penn State AE
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PEX Plumbing Failures
PEX Plumbing Failures
Cadell Calkins, BAE/MAE, Penn State, 2011
Table of Contents
PEX Plumbing Failures
History and Use of PEX Plumbing
PEX Production Process
As the price of copper continues to rise, more economical plumbing solutions are needed. To accomplish this, synthetic materials are being used and the most prevalent in recent years seems to be PEX plumbing systems. Cross-linked Polyethylene, PEX, has gained in popularity in the heating and potable water plumbing because of its ease of use and less fittings. Compared with copper or polyvinyl chloride (PVC) piping, PEX can bend around corners where a copper or PVC pipe would need an elbow fitting. On the practical side, this means that PEX can be easier and quicker to install than copper or PVC plumbing systems.
However, recent failures and the lawsuits that have followed those failures lead to the idea that PEX plumbing systems aren't as good as once assumed. PEX systems can fail in either the pipe or in the fitting. The most notable failure occurs when the fittings fail and water starts leaking and causing visible damage. This article will examine the failure of PEX plumbing systems by studying the history, use, and production of PEX as well as the types and causes of failures and the lawsuits that have ensued.
History and Use of PEX Plumbing
Cross-linked polyethylene (PEX) was originally invented in the 1950's, (Bellis 2010) but improved by Dow Corning and Thomas Engel in the 1960's. Originally, it was marketed to Europe as an alternative to copper in the heating and plumbing industries. In the United States, PEX has been used since the 1980's for radiant heating systems, but has not been popular for potable water until the recent years. (Rotella 2003) In Figure 1, a typical PEX plumbing installation for a shower fixture can be seen where the PEX piping is joined to a prefabricated copper shower connection.
Figure 1: Typical PEX plumbing installation for a shower fixture. Copyright Author 2011
PEX Production Process
PEX can be formed using one of three processes. The first and most common is referred to as the Engel process. The Engel process relies on temperature and pressure along with peroxide to create the cross-linking during extrusion. The Silane method is done by grafting a Silane molecule onto the polyethylene backbone and with the use of a catalyst, the piping is fed through an extruder. The cross-linking takes place by exposing the tubing to steam or hot water after extrusion. Lastly, the electron beam method, the oldest method, starts by extruding high density polyethylene. After extrusion, the tubing is taken to an electron beam assembly and exposed to a prescribed amount of radiation. The radiation causes hydrogen atoms to release and cause polymer chains to cross link to the open carbon sites. (PEX Products - History)
With the sudden increase in the use of PEX in recent years, failures in PEX plumbing systems have been observed. Failures can be linked to two areas; the pipe and the fitting. The pipe can fail when exposed to chlorine within the water, or over exposure to sunlight before installation. In addition, PEX pipe has also been found to be permeable when exposed to some solutions, including oxygen and some petroleum products, and can leach toxic chemicals from the pipe material. As far as the fitting, the leading cause of failure in a brass fitting used with PEX is caused by dezincification. This causes the fitting to corrode and eventually create leaks.
When working with potable water supplies, it is very common that the water comes from the water treatment facility with a small level of chlorine in it to disinfect the water supply. With PEX piping, chlorine can cause oxidation on the inner wall of the pipe. This effect can be seen in Figure 2, where two types of chlorine are used and a control test of neutral water. (Castagnetti, Mammano, Dragoni 2011)
Figure 2: Detail of PEX piping exposed to chlorine dioxide (A) neutral water (B) and sodium hypochlorite (C). Used with permission from D. Castagnetti, G. Scirè Mammano, E. Dragoni 2011.
To battle the effects of chlorine, manufacturers have added antioxidants to the PEX piping. The antioxidants are provided for sacrificial purposes where the chlorine will degrade the antioxidants first. Once these antioxidants are all degraded, the PEX piping is no longer protected and the piping starts to oxidize quickly before failing. (Reid 2005) To compute the resistance of PEX piping to chlorine, the American Society of Testing and Materials (ASTM) has designated the Standard Test Method for Evaluating the Oxidative Resistance of Crosslinked Polyethylene (PEX) Tubing and Systems to Hot Chlorinated Water (ASTM F2023). (
Haenftling 2010) The standard tests for a 50 year lifetime in regards to chlorine, however the standard does not test for hot and cold conditions in the same pipe or the use of chlorine dioxide. (Clark 2005)
In Europe, the effects of chlorine have not been seen because of two major reasons. Similar to the United States, PEX was used first and primarily as piping for radiant floor heating systems. In this system, chlorine is typically non-existent in the water flowing through the pipes and thus the PEX pipe can't oxidize. However, as a potable water piping system, PEX piping in Europe also does not oxidize as much due to the fact that chlorine in European water supplies is at a very low level. In contrast, the United States uses chlorine in higher levels as a means of disinfecting the water. This higher level of chlorine causes the PEX pipe to oxidize quicker.
When exposed to sunlight for an extended amount of time, PEX piping can break down. Like any plastic pipe, exposure to ultraviolet (UV) light or sunlight causes the molecular structure to break down. This causes the pipe to become brittle and eventually rupture. Most PEX piping manufacturers only allow 30-60 days of exposure for normal piping, and up to 6 months of exposure for PEX plumbing that has had ultraviolet stabilizers added during production. In a similar manner, PEX piping by itself cannot be used outdoors exposed to sunlight. For this kind of use, PEX piping must be used in a protective sleeve. (The Zurn Pex Advantage 2003) To test PEX piping for sunlight exposure, ASTM F2657 (Standard Test Method for Outdoor Weathering Exposure of Cross-linked Polyethylene [PEX] Tubing), is used and the oxidative results are compared to ASTM F876 (Standard Specification For Cross-Linked Polyethylene [PEX] Tubing). (
According to manufacturers of PEX piping, it is a known fact that PEX is permeable to certain chemicals and oxygen. Although oxygen may not be considered an issue by most individuals, it is a problem in closed loop systems. In closed loop systems, often radiant flooring systems, oxygen can cause corrosion of the heating elements. (Reid 2005)
Similarly, when PEX piping is used underground, a process allowable by manufacturers, the piping can come in contact with ground water. In most cases, this is not a problem. However, in areas where the ground water has been contaminated by petroleum products, the gasoline additive Methyl Tertiary Butyl Ether (MTBE), or pesticides, PEX piping can permeate these chemicals through the pipe and into the potable water thus contaminating the water supply. (Reid 2005)
During the Engle process of producing PEX piping, chemical byproducts are often left behind in the pipe. The most prominent are Methyl Tertiary Butyl Ether (MTBE) and Tert-Butyl Alcohol (TBA). The amount these chemicals can leach into potable water is uncertain, but one test of AQUAPEX pipe, manufactured by Uponor Wirsbo, showed MTBE levels of 17 parts per billion (ppb) and TBA levels at 6900 ppb. (Reid 2005)
According to the United States Environmental Protection Agency (EPA), MTBE can be a carcinogen when high levels are inhaled. As far as as ingesting MTBE, the EPA has no definitive data on the health effects and according to the EPA's website, "there is little likelihood that MTBE in drinking water will cause adverse health effects at concentrations between 20 and 40 ppb or below." However, at these levels, MTBE can still make the water undrinkable due to the it's offensive taste and odor. (Office of Transportation and Air Quality 2009) In addition, TBA has been shown to cause cancer and hyperplasia in mice and rats during lab studies. (United States 1995)
When brass pipe fittings are manufactured, zinc is added to the copper alloy to increase the strength of the brass. Because the corrosion of brass is dependent on increasing amounts of zinc, it is recommended to keep the zinc content low (15%-19% of the total alloy). To reduce cost, manufacturers have been turning to high zinc levels (35%+) in the alloy. (Snyder 2011)
When water flows through the fitting, the zinc, due to its weak bond strength at the molecular level, leaches from the brass and creates a powdery buildup. This process is known as dezincification. This buildup can cause a blockage within the fitting. The powdery buildup and blockage can be seen in the video to the right, used with permission from SageWater. (Zinc Oxide Buildup 2009) Also, when the zinc leaches from the copper, it leaves the copper very porous and thus mechanically weak. This weakness can cause the fitting to leak and possibly rupture. (Snyder 2011)
Due to the failures listed above, a civil lawsuit had been filed against AQUAPEX for the piping leaching chemicals into the potable water (Reid 2005) and class action lawsuits against Zurn and Kitec in regards to their respective PEX products for the dezincification of brass fittings. (PHR Consultants 2008) Discussed below are two resolved lawsuits that involve the piping and the fittings of PEX plumbing systems.
While very few lawsuits have emerged dealing with the PEX piping, one major lawsuit in Arizona deals with chemical leaching. In Defren v. Trimark Homes, Ms. Defren purchased a house built by Trimark homes and plumbed with AQUAPEX pipe. She noticed her water had a bad taste, causing her to have the water tested for possible contaminates. A lab found that the water contained MTBE, TBA, and other benzene-like compounds. (Enslow 2008) Uponor Wirsbo was brought on as a third-party defendant (Reid 2005) and later disclosed that MTBE and TBA are by-products of the manufacturing process and could have been leached into the water by the AQUAPEX piping. (Enslow 2008)
Most lawsuits dealing with PEX piping deal with the dezincification of the fittings. Zurn and Kitec, manufacturers of brass fittings for PEX piping, have been involved with lawsuits dealing with dezincification of brass fittings. (PHR Consultants 2008) Kitec fittings have been the target of a 2006 Nevada class action lawsuit where Ipex, the parent company of Kitec, has agreed to pay a $90 million settlement. Kitec settled the lawsuit to avoid any further litigation and has not admitted liability. The Kitec fittings are still sold and used elsewhere without incident. (Eckhouse 2008)
When it comes to deciding to use PEX in one's home or for a client of an installer, certain things must be considered. First, one must consider the potential health risks. If PEX is going to be used for a radiant floor system, health risks are not a problem as the water in the system won't be consumed. However, if the PEX is going to be used for potable water, health risks can be minimized. To accomplish this, be weary of placing PEX piping in soil that is suspected of having petroleum or pesticide contamination. In addition, talk with your local supplier and ask if they have heard of any problems with the PEX piping they sell or if you know of anyone who has a house or building plumbed with PEX, ask them if they have noticed any bad water (potentially from MTBE leaching). Secondly, one must also consider serviceability when choosing PEX. This can mean less fittings for the contractor to hookup during installation, but it can also mean the lifetime of the fittings. To alleviate the concern of the lifetime of the fittings, ask your supplier if they have had any customers come back after a failed fitting or a blocked fitting, potentially caused by dezincification. Lastly, when choosing an installer, be sure to choose an installer that you trust. It doesn't matter what type of system you choose, but any fitting can fail if installed wrong and any pipe can break if handled improperly, or in the case of PEX, fail if exposed to too much sunlight. All in all, the choice to use PEX plumbing comes down to a comparison of the benefits, including less fittings and less water hammer effect (PEX vs. Copper Comparison), and the detriments, including dezincification of the fittings and potential health concerns.
As the failures of PEX plumbing continue to be investigated and the lawsuits get settled, contractors will continue to install PEX plumbing systems. Because PEX has just recently become popular for potable water in the United States, PEX has only recently come under additional investigation. Even though research has shown that water flowing through PEX piping could become toxic, it hasn't been confirmed how often this occurs. Similarly, while Zurn and Kitec fittings have allegedly failed, research has not yet determined if PEX fittings are bad or if the manufacturing process was faulty. In the end, the choice to use PEX plumbing systems will be a decision by owner and with PEX costing less than rigid piping systems, it comes down to the owner's acceptance of the risk vs. cost of PEX as opposed to rigid piping.
Bellis, Mary. (2010). "The History of Plastic."
History of Plastics
. About.com. Web. 15 Nov. 2011. <
A timeline of the history of plastic. This source was used to determine when HDPE was invented.
Clark, Robert A. "RE: Use of PEX for Potable Water Plumbing." Letter to California Building Standards Commision. 29 June 2005. Web. 13 Dec. 2011. <
A letter where Mr. Clark presents his views on PEX and mentions the ASTM standards that go with PEX plumbing systems.
D. Castagnetti, G. Scirè Mammano, E. Dragoni, Effect of chlorinated water on the oxidative resistance and the mechanical strength of polyethylene pipes, Polymer Testing, Volume 30, Issue 3, May 2011, Pages 277-285, ISSN 0142-9418, 10.1016/j.polymertesting.2010.12.001. <
A good research paper on the effects of chlorine on polyethylene pipe. Figure 2 comes from this paper.
Eckhouse, Brian. "Kitec Maker Agrees to Pay $90 Million over Pipes."
Las Vegas Sun
. 2008. Web. 13 Dec. 2011. <
Newspaper article about the Kitec lawsuit coming to a close and detailing how some fittings fail while others are still just fine.
Enslow, Thomas. "Comments of Coalition for Safe Building Materials on the Recirculated Draft Environmental Impact Report on the Adoption of Statewide Regulations Allowing the Use of PEX Tubing." Letter to Valerie Namba. 14 Nov. 2008. California Department of General Services. Web. 15 Nov. 2011. <
A letter that discusses the environmental impact of PEX tubing and discusses the case of Defren v. Trimark Homes.
Haenftling, T. (2010). Sitting in the sun.
PM Engineer, 16
(10), 16-16. Retrieved from
Some articles have stated that sunlight exposure can cause failure of PEX piping and this article details about the exposure and the ASTM standards that apply to sunlight and chlorine exposure.
Office of Transportation and Air Quality. "Drinking Water | Methyl Tertiary Butyl Ether (MTBE) | US EPA."
US Environmental Protection Agency
. 5 Feb. 2009. Web. 13 Dec. 2011. <
A credible website that discusses the effects of MTBE in regards to humans.
"PEX Products - History." (No Year).
PEX Products - History
. Plastic Pipe and Fittings Association. Web. 21 Oct. 2011. <
A detailed description of the history and the production of PEX piping. The credibility seems reasonable because it is a manufacturer website.
"PEX vs. Copper Comparison." (No Year).
Plastic Pipe and Fittings Association
. Web. 13 Dec. 2011. <
A small report detailing the comparison between PEX and copper, in particular the water hammer effect.
PHR Consultants (2008). “Section 1 - PHR Consultants Report.”
The Current Status of PEX Piping in California,
Santa Cruz, CA. Retrieved from
Only in a partial form, the entire report would be a good source if I can find sections 2 through 5. As it stands, section 1 contains a lot of information, but nothing that goes in to depth on the problems with PEX.
Reid, Thomas. "Re: Comments on California Department of Housing and Community Development Consideration of the Use of PEX as Potable Water Pipe." Letter to Thomas Enslow. 15 July 2005. MS. Retrieved from
Very detailed letter describing the problems of PEX plumbing systems to the California Department of Housing and Community Development. Good source of information on the problems with the PEX piping with leaching and permeability.
Rotella, K. (2003). Plumbing with PEX.
Plumbing & Mechanical, 21
(1), 62-62. Retrieved from
“Plumbing with PEX” is a very informational source that describes all the benefits of using PEX over other types of plumbing systems. The article may be a little bias as it does not mention any drawbacks due to PEX plumbing systems.
Snyder, Daniel. "Facts About PEX Tubing and PEX Fitting Dezincification."
. Google, 24 Oct. 2011. Web. 15 Nov. 2011. <
A good article on PEX and a good explanation on dezincification. The article is lacking in references and thus the credability of the article can be questioned.
United States. U.S. Department of Health and Human Services. National Toxicology Program.
NTP Technical Report on the Toxicology and Carcinogenesis Studies of T-butyl Alcohol (CAS No. 75-65-0) in F344/N Rats and B6C3F₁ Mice (drinking Water Studies)
. Research Triangle Park, NC: U.S. Dept. of Health and Human Services, Public Health Service, National Institutes of Health, 1995. Print.
A large report on the effects of TBA ingestion in mice and rats. Very informative since similar results can be expected of humans.
The Zurn PEX Advantage. (2003). Zurn Plumbing Products Group.
. Web. 15 Nov. 2011. <
brochure that describes in the frequently asked questions section many different failures of PEX.
Zinc Oxide Buildup
The Danger of Dezincified Brass Fittings
. SageWater, 2009. Web. 13 Dec. 2011. <
Since 1988, SageWater has been a specialist in repiping buildings with there One Call Repipe approach. They have replaced many PEX systems due to faulty fittings and the video of dezincification comes from their experience.
Brown, J. (2008). NSF standards require stringent testing for PEX piping.
PM Engineer, 14
(9), A14-A14,A13. Retrieved from
Since one article states that only one type of PEX piping will pass NSF standards, this article better explains the standards and why might PEX fail these standards.
Holohan, D. (2002). Concerns about PEX and chlorine.
Supply House Times, 45
(4), 60-60,62. Retrieved from
According to the abstract, chlorine may cause problems in PEX piping when used in recirculation systems. This seems to be a very good resource, however I have yet to find the full text.
"In Re Kitec Fitting Litigation."
KITEC® Class Action Informational Website
. Web. 15 Nov. 2011. <
Currently waiting on owner permission to use Figure 3 that was obtained from this website.
South Bay Piping Industry
. Web. 15 Nov. 2011. <
A collection of articles that detail the failure of Kitec fittings by dezincification.
Mader, R. P. (2003). PEX blamed for failures.
(3), 1-1,44+. Retrieved from
More of a newspaper article, “PEX blamed for failures” states that a problem with a PEX system has developed after a television news program smeared the PEX manufacturer. The article goes on to say that the fault may be with the installer and not the manufacturer.
Volkert, L. (2007). Faulty plumbing fittings found in treasure valley homes.
The Idaho Business Review,
(87504022), n/a. Retrieved from
Many articles state that the fitting is actually the cause of PEX failures and this is just one instance of that happening. This article attributes the failure to a Zurn PEX failure.
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