Is there any new information on the relative safety of PEX plumbing material?


Is there any new information on the relative safety of PEX plumbing material?

Asked by Wendy Smith

I will be replacing some of my plumbing lines and am trying to decide whether to spend the extra money on copper rather than use the PEX recommended by my plumber. When I did a search on PEX safety and leaching, most of the information I found was from 2010, I'm assuming around the time that California was considering approval of the material. What I read provided no definitive answer about the safety of PEX. Is there any updated information since that time? My biggest concern is leaching into my drinking water. Thanks!

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Polly Osborne, FAIA, LEED AP's picture

PEX, or cross linked polyethylene, has had some growing pains, like all building materials.

  • The building industry doesn't like change, because that requires a new set of skills and knowledge, and learning on the job can be devastating in this litigious world.
  • The failures and lawsuits related to PEX have mainly been from failure of the fittings and not the piping itself.

PEX is quickly replacing copper in use in homes. It is considered safe to use and approved in most jurisdictions. Manufacturer's recommendations must be followed to ensure the the quality of the product is not compromised.

Copper vs PEX

If you are trying to decide between copper and PEX you will be faced with a barrage of pros and cons and feel like a cartoon with a big question mark over your head!

Traditional copper can leach lead into the water system if it has been soldered with lead as older pipes were, but even later soldering fluxes can be corrosive to copper.

  • Copper can be affected by acid in the water and can develop pin hole leaks.
  • The longevity of copper is considered to be twenty-five years, although, of course, it is much older than that in many buildings.
  • Lead in copper and brass piping systems are a documented serious health concern.

I have used PEX but am always aware that tomorrow a new study could come out that says I shouldn't.

  • PEX is resistant to acid, better in freezing conditions, and doesn't scale or corrode.
  • If properly installed, it is reputed to have the same life-span as copper. (ASTM F2023 assumes an adjusted lifetime of 25 years, while the NSF P171 standard assures a 40 year adjusted lifetime.)
  • To be sure, Pex must be installed according to the manufacturer's requirements. First and foremost, no exposure to sunlight.

Also PEX is vulnerable to failing if over exposed to chlorine, which can cause oxidation to the inner wall of the pipe.

A study of leaching from PEX

The most recent study I've found on PEX chemical leaching is from 2011 by the Norwegian Institute of Public Health, published in the Journal of Water and Health. They examined ten different types of PEX pipes used in delivering drinking water for odor and taste as well as evidence of leached chemicals from the plastic.

According to the abstract (here):

  • "The objectives of this study were to investigate migration of volatile organic compounds (VOCs) from cross-linked polyethylene (PEX) pipes used for drinking water produced by different production methods, and to evaluate their potential risk for human health and/or influence on aesthetic drinking water quality."
  • "The levels of VOC migrating from new PEX pipes were generally low, and decreasing with time of pipe use."
  • "2,4-di-tert-butyl phenol and methyl tert-butyl ether (MTBE) were two of the major individual components detected."

As you can see from this, one chemical that showed higher than average leaching and is a carcinogen was Methyl Tertiary Butyl Ether (MTBE), but it disappeared in most of the pipes after five months of use. MTBE has previously been a concern as something inhaled because it is a by product of gas production. Ingestion by drinking isn't as well studied.

The report is available to read and form your own conclusions here.

Other plastics

Other types of plastic, such as PolyVinylChloride (PVC), are used in the piping of water from reservoirs through municipal domestic water systems, and are more controversial than PEX.

Do you know what kind of pipe your water supply is using?

I hope I've helped

Or is the question mark still over your head? I think we all need to be diligent in following the reports as they emerge.

For more information:

Read "Is the use of PEX -- the plastic tubing for water piping in homes -- green?" a Q&A answered by Polly Osborne.