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Get to Know PEX

Relatively speaking, cross-linked polyethylene (PEX) pipe hasn’t been in the United States for very long. PEX’s flexibility and tolerance of temperatures ranging from below freezing to 200 degrees Fahrenheit makes it ideal for hot- and cold-water plumbing systems, hydronic radiant heating systems, snow-melting applications, and even ice rinks and refrigeration warehouses.

Why PEX?

PEX differs from rigid pipe in one obvious way: it is flexible. This makes it easier for you to snake it to different areas of a building. You may have to run more pipe, but there are far fewer fittings, which may attract many plumbers, says Joe Wiehagen, senior research engineer for the National Association of Home Builders (NAHB) Research Center.

What’s more, all fittings in a PEX system are mechanical, which appeals to some plumbing contractors, Wiehagen says. “There are those that say they can install and solder copper piping in the same amount of time as mechanical fittings,” he adds. “It depends on your preference.” Either way, mechanical fittings allow the PEX system to be pressure tested immediately.

Because PEX has fewer fittings and the ability to bend, you can choose from different design options: manifold systems, tree and branch systems, remote manifold systems and combinations.

Furthermore, working with PEX is fairly intuitive. “In our experience with plumbers installing PEX tubing is that they get the hang of it after a couple installations,” Wiehagen says. However, more experience is needed when dealing with different manufacturers of PEX tubing because most of them produce the tube and fittings differently, and they rarely match up, he adds.

Consider extolling the virtues of PEX to your clients; their decision to implement a PEX system could be a win-win for you both. They reap the benefits, and you spend less time on service and installation. In fact, the cost of home-run plumbing system materials are often less than similar rigid-pipe systems, though it depends on system design, house size, your distributor and product availability.

Let your clients know these advantages the next time you have to make a service call:

  • PEX is quieter than rigid piping
  • PEX has a smooth interior that resists scale build up and corrosion, which can affect the pipe flow over time
  • PEX is freeze-break resistant, although not freeze-proof
  • PEX systems have attractive installation costs compared to rigid materials

About half of the new-home starts in California are installing PEX systems, says Mike Cudahy, codes and training specialist at the Plastic Pipe and Fittings Association (PPFA). This is due in part to the corrosion of copper pipe in some areas, and because of copper price fluctuations.

Go Green
PEX pipe often is used in green buildings, installed either as a remote manifold or plumbing system, Cudahy says.

In a parallel system, each fixture has a dedicated smaller diameter PEX tube run directly from the hot-water source, which means a thinner pipe may be used for the entire connection, reducing the volume in the line. Therefore, waiting times for hot water are reduced and less water is purged down the drain, Cudahy says.

Keep It Indoors
PEX, with all its benefits, does have some drawbacks. For one, it is not suitable for outdoor use because of UV exposure, which causes a reaction with the polyethylene. The maximum-level of UV exposure typically is no more than 60 days, but varies by manufacturer.

Furthermore, there are some chemical exposure concerns to consider, such as burying the pipe. Using PEX for underground water supplies is not ideal, even if UV exposure is decreased.

There is another kind of PEX piping that is used in residential and commercial applications and in pressure service on compressed air and compressed gas systems. It is known as crosslinked polyethylene-aluminum-crosslinked polyethylene (PEX-AL-PEX).

PEX-AL-PEX composite tubing resists corrosion and chemicals and capitalizes on the pressure capacity of metal by laminating the aluminum layer between layers of plastic. The tubing also bends for form stability and resists most acids, salt solutions, alkalis, and fats and oils, according to the Plastics Pipe Institute’s (PPI) Plumbing and Heating Division.


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