Considerations When Plumbing with PEX Pipe

Bruce Davis Sr.
Written by Bruce Davis Sr.
Updated June 15, 2021
pex pipe plumbing
PEX piping has become the rule, rather the exception, for the plumbing industry. (Photo courtesy of Hugh J. Lofting Construction Management Services and Hugh Lofting Timber Framing)

PEX is the plumbing industry's go-to, but many still have questions about the popular piping product.

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All water piping used to be metal. But about a quarter century ago, plumbers in the United States started using a system called PEX pipe, which had been used in Europe for several decades.

PEX is polyethylene pipe that has been changed by one of three methods into a cross-linked material. Cross-linking alters the performance of the original polyethylene pipe and substantially improves it so that it can better withstand pressures and temperatures in domestic hot and cold plumbing systems. Still, it remains very stable chemically and very flexible.

The plumbing system matters when picking PEX

We often receive questions about PEX pipe, such as:

What are the differences between the several brands?

Which PEX is best to use?

Is there any PEX pipe or tubing I should avoid?

The answers to these questions always depend upon the plumbing system — what it will carry, as well as where and how it will be used. Factors include:

1. Will the application be domestic potable cold and hot water? Will it carry water for heating systems, such as radiant and/or baseboard heat, or a different liquid used for commercial processes?

2. Will the system carry clean, soft water, chlorinated water or hard, aggressive or acid water? Will it be a pressurized static system or will any part of the system circulate full- or part-time?

3. Will the system be located underground, hidden behind walls in a living space or inside an unheated space? Will it be surface-mounted and exposed to ultra-violet light, whether natural sunlight or artificial fluorescents?

Plumbers must consider every possible aspect of the plumbing system, and then the piping or tubing system can be chosen based on those factors.

PEX piping must comply with national standards

In the U.S., any system that’s sold for use as a potable water system — PEX or not — is required to comply with NSF/ANSI Standard 61: Drinking Water System Components. Another organization that tests and rates the systems we use is ASTM International. Founded as the American Society for Testing and Materials, it’s a nonprofit that develops and publishes approximately 12,000 technical standards, covering the procedures of both testing and classification of materials of every sort.

To my knowledge, all PEX piping or tubing systems that have been approved by every plumbing code used in the U.S. have undergone testing and received a rating for NSF/ANSI 61 and ASTM International. So, once we know the details and specifics of our system, we need to check and see that it conforms to NSF/ANSI 61, and also see how ASTM has rated the PEX systems we are considering. Then we’ll be able to see what system would work best for us.

Additionally, I think it’s good to talk with a professional who has used the system being considered to make sure that both the piping/tubing and the fitting/connection method have held up well in real-world applications.

The cause of PEX fitting failures

We started to use a brand of PEX piping over 25-years ago for domestic potable water that rated very well in every category. PEX was a great solution. However, after several years we found that we started to get a leak or two on houses that we had re-plumbed with the PEX system. The plumbing leaks appeared in the same place — next to a fitting where there was a thick band of PEX squeezing down on the fitting to make it watertight.

After extensive research, I discovered that wholesale suppliers were not keeping those PEX bands protected from artificial U.V. in storage. Depending on the type, all PEX is sensitive to U.V. in varying degrees and can only be exposed to it for 30, 60 or 90 days maximum. Some of the fittings were being exposed beyond what the manufacturer recommended.

Consequently, we changed systems so that all the fittings are made watertight by crimping a stainless steel band onto it. We’ve never had another leak due to a materials issue.

PEX piping is a trusted plumbing solution

These days, installing metal piping for either potable water or heating systems is the exception, not the rule. A PEX system that is wisely chosen and carefully and properly installed in accordance to both the manufacturer’s recommendations and the local building code will outlast and out-perform any other system. It takes a little more careful planning than in the “old days,” but the benefits are worth it!

Are you considering PEX for your next plumbing project — or do you prefer metal? Share your thoughts in the comments section below!

As of Jan. 26, 2016, this service provider was highly rated on Angie's List. Ratings are subject to change based on consumer feedback, so check Angie's List for the most up-to-date reviews. The views expressed by this author do not necessarily reflect those of Angie's List.

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