Before You Plumb with P.E.X. Read This!


It used to be, that all water piping was metal pipe. About a quarter century ago we in the U.S. started using a pipe system called P.E.X. pipe, which had been used in Europe for several decades. P.E.X. is simply polyethylene pipe that has been changed by one of three methods, into a ‘crosslinked’ material. Crosslinking alters the performance of the original polyethylene pipe and substantially improves it in several ways so that it can better withstand pressures and temperatures in domestic hot and cold systems, while it remains very stable chemically and very flexible.

We are often asked questions about P.E.X. pipe/tubing…
• What are the differences between the several brands?
• Which P.E.X. is best to use?
• Is there any P.E.X. pipe or tubing I should avoid?

…And the answers to these questions are always governed by the system; what will it carry, and where and how will it be used. Here are the specifics:
1. What will the application be?
• Domestic potable cold and hot water?
• Heating System; radiant and/or baseboard?
• Another, different liquid used for some commercial process?
2. What liquid will be carried by the system?
• Is it clean, soft water?
• Will the water be chlorinated?
• Is it hard, aggressive or acid water?
• Will it be a pressurized static system?
• Does any part of the system need to circulate full or part-time?
3. Where will the system be located?
• Hidden behind the walls of an occupied living space?
• Inside a structure, but not in a heated space?
• Underground?
• Surface mounted and exposed to ultra-violet light; either natural sunlight or artificial from fluorescent lights?

The point is that everything possible needs to be considered regarding the system that is being built, and then the piping/tubing system can be chosen based on those things.

In the United States, any system that’s sold for use as a potable water system (P.E.X. or not) is required to comply with NSF/ANSI 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.

As far as I know, all of the P.E.X. piping/tubing systems that have been approved by every Plumbing Code used in the U.S. have been tested and rated to NSF/ANSI 61 and by 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 P.E.X. 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 has held up well in ‘real world’ applications.

For example, over 25-years ago we started to offer and use a brand of P.E.X. piping for domestic potable water that rated very well in every category. We liked offering a P.E.X. system, because in the Pacific Northwest where we live and work, our drinking water is almost exclusively snow-melt, surface waters; not from wells. The water is very clean, but because it’s so pure with extremely few minerals in it, it’s strongly aggressive. We learned that many of our clients who have copper water pipes were experiencing ‘pin-hole’ leaks after about 15- years. It was not due to ‘acid water’; the ph was neutral. And it was not due to improper or non-existent ‘grounding’ from the electrical system; we checked carefully. Sometimes, the water is so clean its ‘hungry’, and it eats into the copper pipe.

P.E.X. 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 P.E.X. system, and the leak was always in the same place; next to a fitting, where there was a thick band of P.E.X. squeezing down on the fitting to make it watertight. After extensive research, I discovered that wholesale suppliers were not keeping those P.E.X. bands protected from artificial U.V. in storage, and some of them were being exposed beyond what the manufacturer recommended (depending on the type, all P.E.X. is sensitive to U.V. in varying degrees and can only be exposed to it for 30, 60, or 90 days maximum).

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

These days installing metal piping for either potable water or heating systems is the exception and not the rule. In our experience a P.E.X. system that is wisely chosen, and carefully and properly installed in accordance to both the manufacturer’s recommendations and the Local Building Code, is a system that will outlast and out-perform any other type of system. It takes a little more careful planning than in the ‘old days’, but the benefits are worth it!

Bruce Davis, Sr.
Licensed Journeyman Plumber
Licensed Electrician, HVAC/R
Electrical Administrator, HVAC/R
Certified WA State C.E.U. Instructor
Bruce Sr is President of Day and Nite Plumbing and Heating,
a 61-year old family owned and operated plumbing and heating
business in Lynnwood, Washington.

Bruce can be contacted at:

Day & Nite Plumbing & Heating Inc.
16614 13th Ave. W.
Lynnwood, WA 98037



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