Is the use of PEX -- the plastic tubing for water piping in homes -- green?


Is the use of PEX -- the plastic tubing for water piping in homes -- green?

Asked by Jim Stephens

As a Habitat builder, we are concerned with the use of products that give off VOCs or other noxious or toxic vapors. Will we find out 20 years from now that PEX isn't any better than copper with lead sweated joints?

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Polly Osborne, FAIA, LEED AP's picture

Every new product has the challenge of coming up against its time-honored predecessor.

  • Copper has been around a long time and lasts a long time.
  • All plumbers are comfortable using it, so there isn't a learning curve.

The first time we specified PEX, I was a nervous nelly, afraid of breakage, rat damage, and offgassing.I've calmed down a lot and think it is a good product.

But you are so right: what will they discover in twenty years? The good news is that they have been using PEX in Europe since the 60s.

What is PEX?

To back up a bit: PEX is high-density cross-linked polyethylene flexible tubing used in many localities today instead of traditional copper piping for plumbing.

PEX has been used for years for medical tubing in such things as IVs and is considered a safe alternative to copper.

  • It has proven resistant to chlorine, scale and tested up to temperatures of 120 C. Normally it is rated from below freezing to 200 F.
  • Like any manmade material, its quality depends on its manufacturing.
  • PEX piping and fittings are regulated here in California and must meet specific code requirements to avoid leaching contaminants into the water. International standards are set by ASTM.
  • All current model plumbing codes approve PEX, although some jurisdictions use an older version code that may not include it.


Copper is recyclable, resellable and valuable throughout its lifetime. PEX is less stable. With time, it becomes harder. This makes it more difficult to reprocess into something else. Studies of how to recycle it and if it can be recycled are still underway.

Let's just say, right now, copper is a lot easier to recycle.

Cost and ease of installation

Copper has become very expensive. If you have the right tools and know what to do, PEX is cheaper and faster to install, because you don't need all the joints you do with copper.

PEX can be used with hot or cold water, and can be used with metal and PVC piping. Most failures with PEX have been in the fittings or installation, not in the pipe itself. It is important to use high-quality brass fittings, with a low zinc content (about 19% max) to avoid corrosion. It is also important to understand what the pressure issues of the given job are.

Limitations of each material

Copper must have a separation between it and other metals. PEX doesn't need this.However, PEX is sensitive to ultraviolet rays so cannot be used where it is exposed to the sun, whereas copper can.

PEX has better burst resistance to frost.

PEX doesn't corrode like copper does, but being plastic, it is possible it could receive contamination through fire damage or introduced toxins.

What's your advice, experience?

I would love to hear others on this, as I feel I haven't given a definitive yea or nay here. We architects tend to know a little bit about a lot of things, but one thing is for sure: we don't like specifying things that might hurt people.

However, with all the attention PEX is receiving these days, I think we will have very definitive answers sooner than 20 years from now!

For more information:

You should read architect Tim Montgomery's Q&A "I am looking for a kitchen faucet that does not have flexible plastic supply lines. I want all copper. How do I find one?"

You should also read Michael Heacock's Ask A Pro Q&A,"I'm seeking bids to repipe my house. PVC is recommended by all three plumbing bidders. Is it safe?"