June 18, 2021

Professional Tool Reviews for Pros

What is PEX Pipe for Plumbing?

What is Pex - Milwaukee M18 ProPex Expansion Tool

What is PEX pipe? Before we answer that question, let’s look at history, lest we doom ourselves to repeating it. Take a look at the water lines in any older house. You’ll probably find one consistent material being used: brilliant, shiny copper. Sorry, did I say brilliant and shiny? Scratch that. Look for copper tubing with dull, bluish-green scabbing all over it.

For the longest time, copper was used everywhere in both residential and commercial settings for their water distribution systems, which to a plumber meant a lot of torch time. We had to solder each and every connection in the building. If you missed a solder joint or had a bad joint, you wouldn’t find out until water pressure was put into the system. If it leaked, you would have to drain the system (after many choice words not suitable for this article), sweat the problem connection apart, dry it, re-clean it and then re-solder. This all takes A LOT of time so manufactures went out in search of an easier and more cost-effective way to transport water throughout the building. And did I mention that copper is freaking expensive!?

So what is PEX pipe? It’s an alternative to copper and PVC water lines. And while it’s been around for some 50 years now, it’s gaining momentum in the residential plumbing sector.

In this pursuit, PEX tubing (also known as cross-linked polyethylene for the nerds in all of us) makes the running of water lines a heck of a lot easier and cheaper than copper. But to make life more interesting the developers came up with three different grades of PEX – A, B, and C.

What is PEX Pipe? Three Grades

The different ratings you see on PEX (A, B, and C) refer to the manufacturing process rather than thickness ratings. PEX-A uses a peroxide method, PEX-B gets silane, and PEX-C goes through an irridation process. But those processes result in different characteristics and each manufacturer has to choose what they’re going with.

PEX-A (Major Manufactuer: Uponor)

PEX-A offers the highest flexibility of all the PEX types available and offers the highest degree of cross-linking. Users can repair kinks in the tubing using a heat gun as well. PEX-A has no coil memory, which means that it won’t try to return to its original shape in the coil. One of the downsides to PEX-A revolves around price; PEX-A costs anywhere from 100%-160% more than PEX-B. It also bursts at lower pressures than PEX-B. This type tends to lack consistency in wall thickness, and because of the manufacturing process, PEX-A tends to display a higher rate of chemical leaching. This can cause concerns in plumbing applications.

difference between cpvc and pex

PEX-B (Major Manufacturer: Viega)

PEX-B displays a high resistance to chlorine and oxidation and offers the highest bursting pressure. Because of these qualities, PEX-B can last up to 40 years, making it a solid choice for plumbing applications. It costs less than PEX-A and PEX-C and has the lowest dimensional tolerances. However, it is more rigid than the other two PEX types, and it displays noticeable coil memory. It offers a lower cross-linking ratio than PEX-A. As opposed to being able to fire up the heat gun, repairs generally have to be made through splicing the piece, and then coupling it back together.


PEX-C is the newest of the PEX types and offers little to no coil memory. It is more pliable than PEX-B, and in terms of manufacturing processes, it is more environmentally friendly. However, PEX-C shows a tendency to develop cracks, kinks easily, and does not cross-link particularly easily. It has even suffered from involvement in a class action lawsuit for its proneness toward early oxidation.

4 Methods to Install PEX Pipe

SSC – Stainless Steel Clamp

The clamp-ring connection method involves sliding a ring over your PEX tubing, and then your tubing over a specialized fitting. The ring is then positioned over the middle of the fitting’s male end, and tightened down with a stainless steel clamp ring crimping tool. Closely related to the clamp method is c=standard crimping.


The push-fit method requires no tools, but does require special couplers. The PEX is pushed into the specialized coupler, which contains a stainless steel barbed ring. The ring closes itself around the PEX tubing. This method is one of the easiest of the connection methods.


The expansion method uses a specialized tool that expands the end of the PEX tubing so that it can fit over a brass fitting. A plastic sleeve slides over the connection point. After the PEX tubing shrinks back down to its original shape around the fitting, you’re done! The expansion method is quick and reliable. Check our installation guide for PEX expanders.

What is Pex - Milwaukee M18 ProPex Expansion Tool


Compression fittings involve an insert that gets pressed into the end of the PEX tubing. A nut and a nylon sleeve slide over the end of the tube. The PEX then slides into the fitting, where the nut tightens down over the sleeve, sandwiching the PEX tubing between the fitting and the nylon sleeve.


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Where did you find PEX A leaches more? I’ve always herd PEX A is the safest, although all PEX leaches chemicals in the water.

Austin Bradly Roach

If you go PEX, go with Uponor!


There is an error in the explanation of expansion method. A plastic ring is placed at the connection, a tool expands the pex- A tubing and ring, the fitting is inserted, then ring and tubing contract on their own trying return to their original internal diameter. There is not a second tool to crimp the fittings together with expansion fittings.

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