Applying PEX to Residential Repipes

Flexibility, corrosion resistance, and ease of installation make PEX a good fit for homeowners’ repipe needs. Keep this information in mind.
Applying PEX to Residential Repipes
PEX's flexibility allows it to be installed in tight spaces in homes with minimal disruption to the surrounding walls.

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There are about 133 million houses in the U.S. More than one-third of these structures (44 million) are over 50 years old; about two-thirds (88 million) are more than 30 years old.

What does this mean for you? With new-housing starts around 1.2 million, there are about 40 times more homes needing repiping than new homes being built. Essentially, there’s money to be made with plumbing repipes.

Most homes were plumbed with copper or galvanized steel pipe 50 years ago, and they are now corroded and need replacing. For a residential repipe, if you’re not doing so already, you may want to consider using PEX. Homeowners could be reluctant to replace copper with copper out of concern that it will just corrode again. With CPVC, because it’s rigid, it’s harder to install in existing walls, so you’ll have to cut bigger holes and homeowners will likely not be happy with that, either.

Instead, PEX is what many repipe plumbers are installing due to its flexibility, corrosion resistance and ease of installation. Plus, PEX comes with a warranty that gives homeowners peace of mind. Here’s some information to keep in mind when applying PEX to the residential repipe market.


The crosslinking of the polyethylene is what gives PEX pipe its strength and flexibility. There are three manufacturing methods for crosslinking polyethylene, resulting in three different types:

  • PEX-a uses the Engel method, which manufactures pipe with more than 80 percent crosslinking.
  • PEX-b uses the silane method, which delivers 65 to 70 percent crosslinking.
  • PEX-c uses the electron-beam or radiation method for pipe that is 70 to 75 percent crosslinked.

Why care about the crosslinking?

The higher the crosslinking percentage, the more flexible the pipe. Translation: You can get it into tighter spaces when repiping a home.

Also, it offers greater shape memory, which means it can expand more to accommodate frozen water in the pipe. This is an important value-add for homeowners.

The shape memory of PEX-a pipe makes it the only PEX that is kink-reparable. If you get a kink in PEX-b or PEX-c pipe, you have to cut in a coupling. If you get a kink in PEX-a pipe, you simply give it a shot of heat from a heat gun, and the pipe will return to its original shape.

The process of removing the kink by heating the tube back to its amorphic state actually makes that area even stronger than before.

Reliable connections

The shape memory also allows the pipe to be used with ASTM F1960 expansion fittings, which work with the properties of the pipe to create a strong, reliable connection. Once the PEX pipe and expansion ring are expanded, they will want to return to their original shapes. If you then insert a larger-diameter fitting, as the pipe and ring return to their normal shape, they will constantly be pressing against the fitting to create a strong connection.

Plus, this connection process — expanding tube and ring to be able to insert the fitting — eliminates the problem of dry-fits. You won’t have to wonder if you remembered to solder or cement a connection. If the fitting is in place, you’ll know the connection has been made. Furthermore, no torches, glues or solders are necessary, which makes for a cleaner, healthier job site.

Other PEX fitting connections, like clamp or crimp, actually work against the properties of PEX. That’s because they’re constantly pressing down on the pipe, forcing it against its natural shape. (Remember, PEX always wants to return to its natural shape.) And because you insert the fitting into the pipe before adding the crimp or clamp, the fitting actually has a smaller internal diameter than the pipe. That will restrict flow — not the best performance for a plumbing system.

PEX: Made for repiping

In the repipe industry, time is of the essence. The faster you can get the old pipe out and the new pipe in (and the walls patched up), the more money you make.

Because of its incredible flexibility, PEX allows you to cut smaller holes in walls. That makes for faster jobs and happier customers. How flexible is it? For PEX-a, it’s six times the pipe’s diameter. That means half-inch pipe can have a 3-inch bend radius. And for 90-degree bends, you can use bend supports that will give you the tight turn without having to cut in an elbow.

Another benefit involves the use of engineered polymer (EP) fittings. These fittings are incredibly strong and durable: The material was originally used in the aerospace and biomedical industries. As a result, they are much more cost-effective than metal fittings. Plus, they’re approved for direct burial, so you can use them in various applications.

Installation tips

Here are some important tips to consider when installing PEX for repipes (or any other plumbing application).

  • Do not apply an open flame to PEX. If you get a kink in PEX-a, it must be repaired with a heat gun, which blows hot air. The temperature of the piping surface must not exceed 338 degrees F (170 degrees C). With regard to heat, do not solder, braze, weld or fusion-weld within 18 inches of PEX in the same waterline. You must make any heat-related connections prior to installing the PEX connection.
  • Store PEX away from open sunlight and direct UV light. PEX must be installed at least 5 feet from UV lighting or 12 inches from recessed light fixtures — unless the fixture is insulation-contact rated. If you have no choice but to install the pipe close to a lighting fixture, protect it with suitable insulation.
  • Brass fittings can be reclaimed, but not EP fittings. As noted, EP fittings are a great, cost-effective alternative to metal, but they cannot be reclaimed from an ASTM F1960 expansion connection. Only brass fittings can be reclaimed from expansion connections. If you need to remove an ASTM F1960 brass fitting, first cut the expansion ring off and then heat the pipe (with a heat gun), so it is easy to remove the fitting. Once the brass fitting is removed, cut at least a couple inches off the pipe to get a clean start on your new connection.
  • Stick with one brand. It’s really important to stick with a single brand when installing PEX pipe and fittings. Pipe and connection methods are designed to work together. Most manufacturers will warrant the product only when it’s used as a system with their pipe and fittings together. Before you start installing PEX, research the manufacturer and its warranty to make sure you and your customers are covered, if needed.

It’s easy to see there’s a viable market for PEX, not only in new construction, but in residential repipes as well. With PEX’s flexibility, durability, warranty and ease of installation, plumbers and homeowners alike are jumping on the bandwagon to add this to their homes or businesses.

If you’re contemplating ways to expand your business and you’re interested in cashing in on the ever-growing repipe market, check out PEX. Learn more about PEX piping systems at and

About the Author
Kim Bliss is the content development manager at Uponor. She can be reached at


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