Q&A / 

PEX or Copper – Which One Should I Use?

PEX cold water lines

These are PEX cold water lines in my daughter’s new home. Each blue tube supplies cold water to a single fixture. (C) Copyright 2019 Tim Carter

DEAR TIM: I have to install some new water supply lines in my home. My current home has copper water supply lines. I’m intrigued by the plastic PEX material and it seems too good to be true. Using PEX I’d only have a joint in my basement and then up at the shutoff valve at the fixture. Hard copper requires many more fittings and lots of soldering. What’s been your experience with both materials and what would you use in your own home? Victoria C., Grand Rapids, MI

I’ve been a master plumber since age 29. You may have the same interest in water supply lines in your own home just like Victoria. The good news is I’ve got deep experience with both copper and PEX water supply lines.

It’s important to realize that I could write an entire book on the topic of copper vs PEX water lines. There’s simply so much information to know about both products and the pros and cons to each. Another key point is there are different types of plastic PEX piping and different systems. With that in mind, I’m going to give you the Cliffs Notes version. You’ll be able to make a sound decision for sure.

I cut my teeth as a young plumber using copper. PEX hadn’t even been invented at the time. Plastic PEX tubing first was introduced into the USA market as a radiant floor heating product in the 1980s. Just over twenty years ago, in the 1990s, PEX started to appear as piping material for use in domestic potable drinking water supply.

Copper is a time-tested water supply line material, but it’s not immune from trouble. There are places in the USA where the water chemistry is aggressive. The water can actually dissolve the copper and cause pinhole leaks and other catastrophic failures. Copper is also subject to splitting if the water in tubing freezes and expands.

Copper is easy to work with. Believe it or not, a homeowner with just a little practice and inexpensive tools can cut and solder copper creating leak-proof joints. It may seem intimidating, but I recorded a video years ago showing how to solder copper in just minutes. You can watch the video by clicking here.

The issue with copper is that it takes quite a bit of time to install a water line from one part of a home to another. You might have five, or more, fittings to get from point A to point B. Each fitting requires you to cut and clean the pipe, clean the fitting, apply flux, and solder. Working with a hot propane torch around wood can be dangerous. Countless house fires have been started by plumbers and DIYers who underestimate how fast a torch can ignite nearby combustible materials.

There’s a newer system to attach fittings to copper tubing without solder. The fittings have a rubber o-ring inside them and an expensive tool crimps the fitting onto the end of the tubing to make a leakproof connection. I doubt you can afford to purchase the required tool. The fittings are also expensive compared to those you solder.

PEX tubing is a magical material. For the most part, you install it like you’d run an electric cable from a circuit-breaker panel to a wall outlet. You snake the PEX tubing through floors and walls from a manifold or adapter in your basement or crawlspace and then end the tubing at the fixture. There are no joints at all that can leak between the two points.

I prefer the Uponor PEX system. You create a leakproof connection using a small PEX collar that slides over the end of the tubing. A tool is used to expand the PEX so it can slide onto the end of a fitting. It’s far easier to create a joint using PEX than copper and I created a Connect PEX video at my website to show you just how easy it is to do.

The PEX tubing has a memory and wants to go back to its original shape so it starts to squeeze very hard onto the ridges on the fitting. After a short time, it’s impossible for me to try to pull the tubing off a fitting. I’ve never ever had a leak with PEX tubing.

Another benefit to PEX is its resistance to splitting when water freezes inside the tubing. In my current home which I did not build, a second-floor water line to a sink always freezes in bitterly cold weather because the builder and plumber goofed up installing the PEX. The tubing has never split and leaked.

You can purchase electric tools that expand the PEX or you can use hand-powered versions. Watch this video of mine to see how easy it is to make up a PEX joint. You couldn't even clean the copper in the short amount of time I can COMPLETE a joint!

Cutting the PEX accurately is important and a simple hand tool cuts the tubing square and perfectly each time. Watch this video to see how easy it is to cut PEX tubing:

You can install PEX as you would a traditional copper system where a larger-diameter pipe supplies water to all the fixtures as the large line snakes through the house. Or, you can install a separate water line from a manifold to each fixture. The manifold method ensures you have no hidden joints or fittings hidden in walls or ceilings, but you end up using much more tubing material.

I’m a big believer in PEX and because it’s so easy to install, I’d use it in any new home I’d build. I just installed over 6,000 feet of hePEX in my daughter’s home for radiant heating and I installed about 1,500 feet of PEX for her hot and cold water lines. We went with the manifold system because I didn’t want any hidden fittings anywhere.

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5 Responses to PEX or Copper – Which One Should I Use?

  1. I've been reading through a few of your articles, I am passing by some things that I would like to comment on only because I'm just coming to the realization that even in plumbing everyone has their opinion on what they like to use for one reason or another. Wanted to add into this article though, I see you mention about the Pex in your own home not splitting or bursting when freezing........ you have been extremely lucky stay aware of it. I don't want people getting a false sense of safety just because they have Pex. I myself (A plumber also) fully back pex and copper equally. There isn't a material out there that will not split or burst under the correct conditions during winter time. Only safe thing to do is condition area and put HOT & COLD side of any exterior wall fixture on a trickle. Alot of people say a drip but long enough in low enough temps a drip is not enough..........I'm in Richmond VA and we get some winters where I describe it as hell freezing over for us and we have pex that splits just like the copper lines will do.

  2. From the photo, I also like that each fixture has its own shutoff valve, and that they are all located in one place, like a breaker panel. With some clear labeling on each tube, one can quickly identify the correct valve to turn off should service be needed to a fixture.

  3. Is there a concern of ingesting plastic micro particulates. Any research in this area.
    Also copper has anti bacterial/fungal properties. Can this be a problem with PEX in the long run?

  4. Copper in the Culpeper Virginia area lasts about 20 to 30 years. The water in this area attacks the copper and erodes it to paper thin at which point it fails.

    The Uponor Pex system is fine, but it is about twice as expensive as Pex B which is usually what is sold in the big box stores. Pex B uses the copper ring or the cinch clamps. The tool for either of these is a fraction of the price of the expansion tool needed for the Uponor (Pex A) system.

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