So you’ve successfully secured an order to provide a plumbing and hydronics system for your customer. You have the best solutions, the right price and are ready to go, but then they have a question. Are you going to use Wirsbo or PEX? What even is the difference?

This is a question we receive frequently at and the short answer is that Wirsbo IS PEX! PEX is slang for “Crosslinked Polyethylene”, a popular type of plastic material used for plumbing and heating pipes all over the world. Wirsbo is simply one of many brand names of PEX in the marketplace. Where it is concerned whether something is “Wirsbo or PEX”, the question actually being asked is usually about the classification system of crosslinked polyethylene.

There are 4 classifications of PEX Pipe, known as PEX-a, PEX-b, PEX-c and PEX-d/PEX-other.  This topic can be explored in greater detail below or in our subsequent article. Each classification refers to the method of inducing crosslinking in the polyethylene chain, and results in different strength, shape memory and flexibility characteristics. On a more practical level, these differences will allow for different connection types to be used with the pipe, which is what we will focus on in this article.

PEX-a is the highest flexibility PEX tubing and popular brands include Rehau, Uponor (formerly called Wirsbo) and VesiPex. Typically, PEX-a is used with cold expansion fittings (F1960) or Uponor / Wirsbo’s brand name Propex fittings. Other expansion fittings that can be used are F2080 or Rehau’s Everloc fitting. PEX-a can commonly also be used with all crimp fitting and push-fit style methods.

PEX-c has traditionally occupied the smallest market share due to a relative scarcity in the crosslinking equipment, but has been gaining traction in recent years, due to its zero-waste byproduct production method. Some PEX-c brands have equal flexibility to PEX-a brands, for example VesiPEX and Uponor both have a minimum bend radius of 6 times the inside diameter of the tubing. Popular PEX-c brands include VesiPEX, Roth and Sharkbite (barrier only). Some PEX-c brands like VesiPEX can also be used with cold expansion fittings like PEX-a. PEX-c can also be used with all crimp fitting and push-fit style methods.

PEX-b is the stiffest PEX tubing and the only classification to have a different molecular structure.  Popular brands include Bow, Watts and Viega. PEX-b can only be used with the various crimp or push-fit style connection methods. It is not recommended to expand PEX-b pipe since it has no molecular memory. More information on this topic is covered in our difference between PEX tubing article.

PEX-d (also known as PEX-other) is the newest classification, which uses UV light and an azobenzene reactant to induce cross-linking.  It was introduced into the marketplace less than 5 years ago and very little is known about its characteristics or long-term performance. Also, currently it is not for potable water use.

Any brand of PEX-a Pipe, as well as VesiPex PEX-c can use a “cold expansion fitting” which is generally considered the most reliable fitting type.  These fittings are full flow, meaning they have the same inside diameter as the PEX Tubing.  Cold expansion fittings are classified as either ASTM F1960 (commonly referred to as “Propex” or “Wirsbo” fittings, though they are not exclusive to that manufacturer) and ASTM F2080 (commonly referred to as “Everloc” or “Rehau” fittings, they they are not exclusive to that manufacturer). Additionally, most other fitting connection options including ASTM F1807 brass crimp fittings, ASTM F2159 polymer crimp fittings and ASTM F2854 push fittings will typically be certified by a PEX-a or PEX-c manufacturer.

PEX-b (i.e. Bow, Watts, Viega) can only be used with crimp or push-fit style fittings, along with copper crimp rings, stainless press sleeves and stainless clamps.  Crimp fittings restrict flow, meaning they have a smaller inside diameter than the PEX, adding pressure drop to the system.

*Pro Tip: All PEX pipe manufacturers will have the ASTM codes of compatible fittings printed on their pipe, so be sure to confirm you are using an approved fitting system before purchasing products.*

Armed with the information, you will be equipped to handle any questions thrown your way about the difference between Wirsbo and PEX, and you can feel confident the next time you order a system that you are purchasing the correct compatible components.  Keep Calm and Plumb On!

For more information on the best system for your project, feel free to contact our design and engineering team.

Other Article Links:

“What are the types of PEX”

“What are the types of PEX fittings”