Pex - Cross Link PolyEthylene

Questions we have asked ourselves about PEX piping:

Are all PEX pipe manufacturers offering the same quality of PEX pipe?

Is all PEX piping the same?

Are all methods of connecting PEX pipe and are all fittings for PEX equal?

Then there is this for us to consider:

There is the PE-Xa (Engel Process PEX with manufacturers Wirsbo and Rehau).

There is the PE-Xb process PEX produced by the silane-method (offered by Vanguard also known as PEX-B).

There is evenPE-Xc (irradiation-method of PEX also known as PEX-C).

There also is available the sandwiched PEX/Aluminum/PEX pipe.

PEX is cross-linked polyethylene and it is not ordinary polyethylene pipe.

PE stands for polyethylene and X for cross-linking.

The material's chemical abbreviation is PE-X.

There is PEX specifically made for potable (drinking) water.

There is PEX made for under floor piping and there is PEX specifically made for radiation type heating.

We realize that not all PEX pipe is the same and that makes it very difficult for us to "know" what is "best."

We offer fittings that can connect PEX to copper, CPVC or polybutylene pipe - just click here

Wirsbo, the quality-oriented manufacturer of AquaPEX (r) - wrote (Product Catalog, dated March 1, 1998)
"Do not use or store AquaPEX (r) where it will be exposed to direct sunlight for more than 30 days."

In Wirsbo's Installation Handbook (May, 1996) it states that if one is unsure of exposure time to sunlight or uv rays, one should "...submit sample of tubing prior to installation."

Cold weather installations?
"In temperatures below 50 degrees, do not hold the tubing in the expanded position for over two seconds."

Cold water durability?
In their warranty, dated May 1,1995:
".....It is expressly understood, that failure as a result of freezing of water within the pipes, or failure as a result of over exposure to direct sunlight, as defined in the current Wirsbo-AquaPEX Installation Handbook, does not constitute a defect in materials or workmanship, and shall not be covered by this warranty....."

US Brass, in Bulletin no: QT-131 (dated October 17, 1996) wrote to their customers:
"Field tests have confirmed that QestPEX (tm) material should not be stored in direct or indirect sunlight.
Failure to adhere to these instructions, as stated in our instructions manual, will void the Qest warranty."

In Reeves Journal, May 1996, page 23, James Hinte, technical engineer for Vanguard plastics (a major, quality-oriented, PEX piping manufacturer) wrote:
".....Cross-linking is a delicate operation-either too much or too little of it can compromise the quality of the finished product....."
Because of the variety of materials used in the PEX manufacturing processes, long term performance is not guaranteed in each case. Users should be careful to consider only pipes which have been tested and shown to meet the requirements of hot water pressure applications."

We received the following letter from Vanguard Piping Systems Inc. in 1999:
(and we have received written permission to quote the letter, word for word)

"I appreciate you notifying your customers that PEX should not be exposed to DIRECT sunlight, however, indirect light will not harm PEX products which are manufactured to ASTM standards and NSF listed. You also list concerns about PEX installation in cold weather and for cold water. The only approved standard for joining PEX is the metallic insert with metallic crimp ring system (ASTM F1807) which is used by more PEX tubing and fittings manufacturers than any other system. Using this joining method, cold installation and cold water durability are not an issue for the installer...period.

The Wirsbo installation, as you stated, is effected by temperature. Their method is not an approved standard for PEX, at this time, and should not be seen as an issue for our industry as a whole.

The PEX market has grown in three years from nothing to over 12% of the residential plumbing market. Vanguard alone has sold literally millions of feet of PEX tubing into the US market. Europe has been using PEX tubing in plumbing for more than 25 years. Currently PEX and PEX composite pipe (PEX-AL-PEX) is the market leader for residential plumbing tubing in most European markets. It is a proven performer and not unlike any other material you purchase, you simply need to find a manufacturer you believe in and who provides the quality and service you require of the product."
Marisa Morales - Sr. Marketing Manager - Vanguard Piping Systems Inc. - April 8, 1999

We received the following letter from Uponor Wirsbo in 2002:
(and we have received written permission to quote the letter, word for word)

"Wirsbo is the world leader in PEX tubing with billions of feet in service for hundreds of thousands of jobs worldwide. Wirsbo PEX tubing is not only the most installed, most field-proven PEX tubing in the world, it is also the most extensively laboratory tested PEX tubing. Over the past 30 years, Wirsbo PEX tubing has been subjected to a comprehensive array of tests that simulate the most extreme operating conditions, including high temperatures, pressures, and high levels of chlorine in open systems.

The information on PEX fitting systems posted on this site is outdated and inaccurate. Wirsbo fittings meet ASTM standard F1960. In addition, successful cold weather connections are done with Wirsbo fittings every day in North America's coldest climates including Minnesota, Wisconsin and Canada. Thousands of trained Wirsbo installers from across the country are proficient at making successful connections using the Wirsbo ProPEX fitting.

In addition to the many national model code approvals carried by Wirsbo PEX, our tubing also meets the requirement for resistance to chlorinated water that is now being incorporated into ASTM F876. The newly revised standard stipulates that all PEX tubing for potable water listed to F876 must pass a minimum 50 year extrapolated "time-to-failure" test for exposure to hot, chlorinated water when tested in accordance with the chlorine test methods described in ASTM F2023.

Wirsbo is a strong supporter of the trade, and as a result, we choose to sell our products to plumbing and heating wholesalers only. Together with our trade customers, we are proud of the proven, reliable performance that Wirsbo systems have demonstrated in actual field installations and laboratory testing over the last three decades. Wirsbo's considerable experience provides a significant measure of confidence to those who have come to depend on Wirsbo quality."
Cindy Albrecht - Uponor Wirsbo - Customer Relations Manager - December 11, 2002

Here is a comment from a plumber who wrote to us (We are not saying that we agree with him. We are only sharing what he wrote to us. We have received his written permission to show you his letter):
"I have been using Wirsbo Pex and have never had a problem with it. I am a professional plumber from Virginia. Their fittings are twice the weight and thickness of Quest. Wirsbo was designed from the ground up as a plumbing system. Quests was designed around the crimp tool they had on the market for their poly pipe. There have also been pressure problems with the quest as it has a smaller diameter then the Wirsbo. I would heartily recommend the Wirsbo Pex with a modified manifold system. I have had no complaints from customers when this was installed.
Thank you,
signed: Jeffrey"
"You may quote me.
Jeffrey Vanhoozer Stuart, Virginia Plumbing for 19 years."
"The Wirsbo system with their modified manifold or home run as they call it makes for one of the finest piping systems I have ever installed. Every customer just loves it when I replace their old system whether hard plastic, copper or galvanized piping."

We offer fittings that can connect PEX to copper, CPVC or polybutylene pipe - just click here

As we understand it, there are basically three ways to manufacturer PEX.

  • The Engel process (Wirsbo is one mfr that uses this method), where the cross linking happens "hot" (in its amorphic state above the crystalline melting point) since the polyethylene, anti-oxidants, and the cross linking initiator (peroxide) are extruded under pressure while in a molten state.
  • The Silane method (Qest is one mfr that uses this method), where a vinyl silane agent is added to the resin/polymer base prior to the extrusion process, thus forming a grafted copolymer.
  • The Radiation method, which involves bombarding previously extruded PE tubing with Gamma/Beta electrons while sealed in a vacuum chamber.
  • "Class Action Lawsuit Filed Against Zurn Pex and Zurn Industries Relating to Failure of PEX Plumbing Systems in Homes.

    ST. PAUL, Minn., Aug. 10, 2007 (PRIME NEWSWIRE) -- Homeowners in Minnesota have filed a class action lawsuit in federal district court against the manufacturer of residential plumbing systems. The homeowners, Denise and Terry Cox from Detroit Lakes, Minnesota, started the nationwide class action against Zurn Pex, Inc. and Zurn Industries after brass plumbing fittings used in their home's PEX plumbing system failed shortly after completion of their new home. The failures caused water and other damage at the Cox home.

    PEX plumbing systems involve flexible plastic plumbing tubes (as opposed to the more common copper plumbing systems) that are attached to brass fittings throughout the plumbing system. 'PEX' is a generic term for cross linked polyethylene -- the material used to make the plastic piping. PEX plumbing systems are the newest generation of non-copper plumbing systems coming into favor after the plumbing industry stopped selling the failure-prone polybutylene pipe systems.

    According to Cox's attorney, Shawn Raiter, the problems with Zurn's brass fittings can cause significant damage to homes. 'Water damage from a total failure, or even a slow leak, can cause serious damage. A large percentage of the brass fittings in a typical residential PEX system are hidden behind drywall or between floors. If undetected, water damage from a leaking fitting can even lead to mold, which in turn can pose a health risk.'

    Over the last six years, Zurn has reportedly sold 139 million of the brass PEX fittings. Because of the premature failures, certain Zurn distributors have subsequently requested and received refunds for the brass fittings. In fact, according to Raiter, Zurn no longer recommends installation of the brass fittings in certain geographic areas. Yet, Zurn currently denies that these failures will continue, much like its predecessor U.S. Brass did before filing bankruptcy because of litigation related to its polybutylene systems.

    Some plumbers have had 150 or more claims related to failed Zurn fittings. And while Zurn initially honored its warranty and covered the damage caused by the failed brass fittings, the company stopped paying claims, leaving homeowners to pay for the damage themselves.

    The Cox's lawsuit seeks to include the claims of all owners of Zurn PEX systems with brass fittings in the United States. The Cox's are seeking damages to pay for the complete replacement of all brass Zurn fittings for PEX systems, regardless of whether those fittings have already failed, as a way to prevent damage caused by future leaks and failures.

    The lawyers for the Cox's recommend that owners' properties with Zurn PEX systems contact them to discuss their rights. 'It is important that consumers are aware of this lawsuit. If consumers provide their contact information, we can keep them informed about the status of the litigation. Also, if the lawsuit is successful -- by settlement or judgment -- contact information can help us notify consumers how to obtain their share of any recovery,' said Shawn Raiter."


    It appears to us that the above mentioned lawsuit only involves failures of the brass fittings themselves and NOT the PEX tubing or the crimp rings.


    A few words of advice regarding PEX from a DIYer.

    March 03, 2007 by Christopher Akins, Springfield, MO. (we have written permission to show his words first shown on Plumbing Forum

    "As a DIY'er - not a plumber - I can offer my thoughts on a first experience with PEX. Just finished replumbing the entire supply system of my 1950's house except from the meter to the house. This included some lines in a very tight, 13" crawl space. That detail may be important to what type of crimp connector or tool you choose.

    After researching the topic a couple years ago on this forum, I was reading that full-circle copper crimp rings were better than side crimp stainless steel so I went with that system despite most contractors around here (Springfield, MO) using the side-crimp rings.

    The tool I used was a Zurn interchangeable jaw crimper to avoid having to purchase two tools. I got it brand new on Ebay with a de-crimping tool for way less than my local Lowes had them. For a newbie to the system, the de-crimping tool came in very handy - actually a necessity. Though my crimps got better as I went, I found the copper ring system to be tricky at times, working alone. So some crimps had to come off.

    My experience after using the system:

    1) I'm happy to say, not one PEX connection leaked after turning on the water, so I'm happy with the copper rings in that regard. I was probably over-cautious and took off any rings that were the slightest bit less than perfect, though. I'd rather do it now than later when something springs a leak.

    2) The tool system I used, similar to a lot of brands, is a pretty long tool that has to open up so the two handles are nearly 180 degrees apart. This can pose a real logistical problem when working between floor joists and under the house in a very cramped crawl space. Most connections in the basement and wall were much easier, though even in those areas there were some tricky spots due to the size of the tool when open and the arc needed to close the tool during the crimp.

    3) The copper ring system with the type of tool I used almost necessitates a person needing 3 or 4 hands at times - especially when doing crimps on a vertical run of tubing. The ring slides down while you're trying to get the tool on it, straight, etc. Even on horizontal sections I felt the rings slid around way to easily while trying to the tool around them, square to the tubing, just the right distance from the fitting, etc. Pretty small tolerances for error overall. I'd love to see the rings be more snug BEFORE the crimp.

    4) A local plumber demonstrated his side crimp tool to me one day. I must say it seemed much easier since he could hold the ring in place with one hand and crimp with the other. It was definitely faster, and cutting the crimp off was way faster too. 'Course some of that was due to the fact that he does this every day of his life and I'm new to it. But still, the side crimp system seemed quicker to me in that regard.

    5) There are offset tools for the copper ring system, though much more expensive. These supposedly allow one handed operation of the tool for the copper ring system. As I'm not a plumber, I couldn't justify the cost - at least before the job. Now that I did the entire job, at times really fussing with the above mentioned challenges, I think the one-handed model might have been worth the nearly 3x cost.

    6) One problem I found with the interchangeable jaw tool vs. two separate tools was that when I changed jaws from 1/2" to 3/4" the tool had to be recalibrated in order to meet the tight tolerances for the crimp being tight enough but not too tight. With two separate tools, I could have set it and forgotten it for the most part. Re-calibration meant making a test crimp or two every time I changed jaws. That equals wasted rings = wasted money and time. I checked nearly every crimp with both a go/no-go gauge and a digital micrometer caliper.

    Hope this long post helps you and someone else out there that is thinking about tackling PEX as a DIY'er. Overall I'd do PEX again for the many benefits. I might consider a different tool system the next time, though."

    Later when we asked the author for his permission to show his words/experiences Mr. Akins agreed and in part also stated: "For the beginning do it yourselfer like myself (first house, first refurb, learning as I go) I think one of the hardest parts of any project is trying to wade through the myriad information and decide what's true and what's not. Even when I've had contractors in to bid a couple projects it's a miracle for two of them to agree with how something should be done! :-) But on the sunlight issue with PEX I actually replaced 3 100' coils of the stuff which I had purchased a year earlier then didn't get to install as originally planned. It had been protected from direct sunlight, but not completely from indirect. I just happened to notice in Vanguard's printed info it spoke of not letting PEX be exposed to direct OR indirect sunlight. Wow - I hadn't seen the indirect word before. So I wrote their company and asked them about that. I not only told them about how my PEX had been stored but explained that I would be putting the piping in a basement that has two windows (indirect exposure) and a crawlspace with two very small vents. They indicated that EVEN IN THE CRAWLSPACE I would need to take measures to somehow cover the PEX. They also said NOT to use the 3 coils of PEX I had already bought if it had been exposed to indirect sunlight for much time at all. So I replaced it. Didn't throw it away as I might use it for something like a sprinkler later. It won't matter as much if it starts leaking a little in the ground, right? But the long and short of it is that I just finished putting foam pipe insulation on every inch of the PEX I installed. I have no idea if it was really necessary or not. My gut says "NO" as I can't really believe that the small amount of diffuse light that makes it into my crawlspace could possibly hurt the stuff. And I know for a fact that plumbers here don't protect their PEX in new home construction. There are 6 brand new homes right across the street from me that have PEX all through their crawlspaces with nothing on the piping. But Vanguard themselves said "NO LIGHT", so I went the extra mile. That's why I was completely surprised to see a quote from them on your PEX page that is contrary to what they told me. That's the part that's so confusing to us newbies. Which person, even from the same company, does one believe? While I feel good about my choice to use PEX and believe it will hold up for the long term, it's the very confusing bits like mentioned above that make me understand why® doesn't yet offer the PEX system."

    Frequently Asked Questions

    Q. "I've heard/read that if pex gets kinked, it can be heated and it will go back to its original form?"
    A. The a, b, or c refers to the percentage of cross linking of the carbon molecules of the basic polyethylene material that becomes PEX during the processing of the material and extrusion into tubing form. The peroxide injection method also known as "Ingel Method" makes PEXa, Silane injection method makes PEXb and e-beam irradiation method is used to make PEXc.

    The methods of processing the material are different to arrive at these similar (but different) PEX tubing. PEXa has the highest percentage of cross linked carbon molecules and so it might be stronger and more flexible than PEXb or PEXc.

    Another PEX out there has been a PEX-AL-PEX that has a layer of aluminum sandwiched between two layers of PEX. This is popular in some circles because you can make it straighter and keeps it's structural shape at higher operating temperatures. It tends to not sag between hangers. The downside of course is it is stiffer and not as easy to work with. Plus, forget heating out a kink!

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