PEX is a type of plastic piping used in buildings. It's an old technology but the variant PEX-A (frequently known by the brand name Uponor) has come to be viewed largely as the better variant because it has expansion fittings (the tube grows over the fitting and it shrinks to its smaller form naturally) rather than compression fittings (the tube is compressed by the fitting itself).

In this video entitled "Zurn PEX-B Expansion vs. Uponor PEX-A Expansion 2020" the narrator demonstrates that the PEX-B in questoin is F1960 Expansion compliant and compatible (fits) with Uponor expansion connections. I'm looking for information on this claim.

I ask Roger Wakefield -- the YouTube plumbing celebrity, and again in this follow-up and in this follow-up. I can't find any information about people and their experience with PEX-B and expansion fittings.

Does PEX-B really support expansion fittings? Is there reason to believe this is safe for long term use (won't rupture)? I've read the stretching like that PEX-A undergoes violates PEX-B's integrity. How is Zurn's PEX-B different (chemical or process)?

2 Answers 2


According to this pamphlet from Zurn,

PEXa (Engel Method), PEXb (Silane Method) and PEXc (Radiation Method) are not ranking systems; they are manufacturing designations. Zurn utilizes a patented variation of the silane method that produces the highest temperature/pressure resistance, optimal flexibility, highest chlorine rating, extended UV resistance, vibrant colors, and the ability to work with both insert/crimp fittings, as well as expansion fittings.

So, whether a given PEX pipe is compatible with expansion fittings is not necessarily a matter of whether it's PEX-A, PEX-B, or PEX-C, but rather is a matter of other characteristics (like elasticity) that correlate with the manufacturing method.

The difference between one company's PEX-B pipe and another company's PEX-B pipe could include temperatures, pressures, durations, and other such variables throughout the process.

Zurn's particular variation on PEX-B officially supports expansion fittings. Apollo, on the other hand, in their 2021 installation manual, explicitly state that "Expansion PEX Tool" is for "Use with PEX-A pipe only". This is likely because Apollo's particular implementation of the Silane Method differs from Zurn's in ways that result in insufficient elasticity or other vital characteristics.

Differing tolerance to liability, from a corporate standpoint, may also play a part in the distinction, as suggested by YouTube user Kathy Morgan's explanation on another video from Integrity Repipe:

Any PEX can be cold expanded but the difference is that each pipe manufacturer has their own policy and position on cold expansion fittings. Cold weather expansion has limits and potential damage can happen with anyone's PEX regardless of PEX-a, b, or c.


Although most PEX-b tubing is not compatible with cold expansion fittings, there are at least a couple brands who make PEX-b tubing that is compatible. Only PEX-b tubing that has the listing for ASTM F1960 (Cold Expansion fittings) will be compatible. Zurn and Sioux Chief make PEX B tubing that are advertised to work with F1960 cold expansion fittings.

PEX B tubing that is compatible with expansion fittings will be a little more flexible than typical PEX B, but it is still stiffer and less flexible than PEX A, so it is harder to work with. However, PEX B does offer better performance than PEX A in terms of chlorine, oxidation, chemical, and UV resistance. Some say that PEX B also leaches less toxins into the water than PEX A, but I have not been able to find test reports and they both can receive ratings for NSF-14, NSF-61, cNSFus-PW.

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