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Types of PEX tubing (A, B, C). Choosing the right type and brand for your project.
What are the differences between common PEX brands?
Is one brand better than the other?
Which type of PEX should I use for my project?
To answer these questions and help installers and homeowners to make an informed decision, we’ve decided to create a guide which is simple and yet offers details for further independent research.
We think it would be fare to disclose to the reader from the start that we sell PEX-B pipe, but for the purposes of this article, would try to refrain from promoting or discrediting any type of tubing unless it’s backed by independent research data.
Classification of PEX by manufacturing process
Regardless of brand, there are only (3) main manufacturing processes used to produce PEX tubing:
Peroxide method (used to make PEX-A tubing)
Silane method (for PEX-B tubing)
Irradiation method (for PEX-C)
Contrary to the popular belief, A, B, and C are not grades of PEX. These letters are used merely to identify the manufacturing process and have nothing to do with quality or performance ratings of the end product except as explained further in the text.
In fact, all of the above have to adhere to the same standard:
Pressure and temperature ratings
Minimum bending radius
Pipe wall thickness and ID/OD dimensions (subject to manufacturing tolerances)
* Note that these only apply to brands sold in the US and mentioned below. There are many little-known or no-brand products out there which may or may not meet these criteria.
More on the dimensions, rating and other technical specifications of PEX tubing can be found here.
All types of PEX (A, B, C) have to comply with the same ASTM F876 and ASTM F877 standards and SDR9 dimensional standard before they can be used anywhere in the US. The pipe which conforms to these standards carries a proper readable imprint.
A brief description of each manufacturing process and some of the leading brands is outlined below:
PEX-A PEX-B PEX-C
PEX-A tubing is produced using Peroxide (or, “Engel”) method, named after the inventor Tomas Engel. During the manufacturing process, free radicals are created when HDPE polymer is melted and cross-links between molecules occur at temperatures that exceed the decomposition temperature of the polymer. PEX-B is made using a "Silane" or "Moisture Cure" method of cross-linking, where links between the molecules of the HDPE polymer are formed after the extrusion process using a catalyst and by exposing PEX tubing to water (steam bath). This type of PEX is probably the most common and is manufactured by a large number of companies. PEX-C pipe is manufactured using “Electronic Irradiation” method of cross-linking, also known as "Cold" cross-linking. Here, cross-linking of the molecules is done after the process of extrusion by exposing the pipe to an electron radiation beam. The radiation emitted allows to break the existing links between molecules of the polymer and initiate cross-linking process.
Uponor (formerly Wirsbo)
Comparing the end product
PEX-A Highest flexibility (softness) among all PEX types.
Kinks can be repaired with a heat gun.
Highest degree of cross-linking.
No coil memory. Highest price (100-160% higher than PEX-B)(1).
Lower bursting pressure than PEX-B.
Possible residual or leaching chemicals from manufacturing process.
Variation in wall thickness.
PEX-B Highest chlorine and oxidative resistance(2)
Highest bursting pressure.
Lowest price vs. PEX-A and PEX-C(1).
Lowest dimensional tolerances. Stiffer than PEX-A.
Lower cross-linking ratio than PEX-A.
Noticeable coil memory.
Kinks can only be repaired by splicing (using coupling).
PEX-C Softer than PEX-B.
More environmentally-friendly to manufacture.
Little or no coil memory.
There’s very little data available on PEX-C tubing to allow for competitive analysis. Prone to development of cracks.
Least resistance to kinks, which are repairable only with a coupling.
For comparison of PEX Fittings and Connection Methods (Crimp, Expansion, Compression), click here.