The Differences Between PEX-A, -B and -C


Developed in 1968 in Europe, PEX pipe came to the U.S. in the mid ‘80s, and for the past 15 years, it has become one of the most common materials used in residential plumbing systems.

When you see PEX-A, PEX-B and PEX-C, you may wonder what the differences are between them and which one you should choose. Below, we break down why there are three kinds of PEX, which traits they share and how they’re different.


How PEX Pipes are Similar

As many of you know, PEX stands for cross-linked polyethylene. The letter that follows simply signifies the type of manufacturing method used to cross link the polyethylene, not the grade of PEX.

If you look in the international plumbing codes, you’ll only see references to PEX, not the different types. That’s because by and large, all PEX pipes are very similar.

They must all meet the same performance standards. There are some requirements that apply to all PEX pipe used for commercial and residential plumbing applications. Others apply to PEX used in specific systems or applications. A few examples include:

  • ASTM F876, which is the performance standard for PEX tubing.
  • NSF/ANSI/CAN 61 when installed in water distribution systems.
  • Standards for specific applications, such as UL 1821 for PEX tubing used in multi-purpose fire suppression systems.

They’re dimensionally the same. PEX size doesn’t change between PEX-A, -B and –C, as defined in ASTM F876. They’re all Copper Tube Size, or CTS.

They all have a Material Designation Code. All PEX pipe is assigned one of these codes based on their level of chlorine resistance, UV resistance and hydrostatic design basis (HDB), or pressure rating.


So What are the Differences between PEX types?

The truth is, not a whole lot. Again, the main distinction lies in the manufacturing method, which is what assigns an A, B or C to PEX.

  • PEX A is made using the Peroxide, or Engel, method.
  • PEX B is formed using Silane, or Moisture Cure, method. This is the most common PEX pipe type out there.
  • PEX C is created using the Electronic Irradiation, or Cold, method of cross-linking.

There may be small variations in density, burst pressure levels and bend radiuses between PEX pipe types, but they’re negligible. There are, however, a couple of key differences to pay attention to no matter which PEX pipe you’re looking at.


The Material Designation Code

This four-digit number changes depending on the chlorine resistance rating and UV resistance rating as determined in ASTM F876. It can be broken down into three parts:

The first digit is chlorine resistance. The highest rating is a Class 5.

The second digit is UV resistance. The highest rating is a Class 3, which indicates a six-month UV resistance.

The last two digits is the HDB, which is the same for all the PEX tubing sold in the U.S. This will be “06,” indicating a 630 HDB, or a pressure rating of 160 psi at 73 F.

The highest code is PEX 5306.




































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