Is PEX Plastic Tubing Better than Copper?

Written by Tim Schreiner

If you go looking for the copper pipes carrying water throughout your new home and can’t find them, look around for strands of flexible blue-and-red plastic tubes. The plastic pipe is PEX—polyethylene cross-linked tubing—the latest word in plumbing.

If your plumber hasn’t started plumbing your new house, or if you are about to remodel your kitchen or bathroom, you might want to discuss the possibility of PEX with your contractor.

Why move away from copper pipe, which has been the standard for 75 years? The quick answer is because PEX is less expensive, faster to install, delivers hot water quicker, isn’t susceptible to pinhole leaks and won’t break when your water freezes. Beyond that, it requires fewer connections (where pipes tend to leak), is repaired easily, is less susceptible to water-hammer noise and is less toxic because it does not require solvents, flux and solder.

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Here are the problems with PEX. The biggest one is that many plumbers are skeptical and don’t know how to install it. In addition, it has to be kept away from direct contact with recessed light fixtures and hot-air vents, and it can’t be left in direct sunlight unless it has ultraviolet (UV) protection built in.

Let’s explore the pluses. Here’s why it is less expensive: It is plastic, so it costs about 50 cents a foot, compared with 85 cents for copper. Fewer joints not only mean fewer potential leaks, but also fewer fittings to buy. The fittings are expensive but, again, fewer are needed.



PEX doesn’t break when water freezes because it is cross-linked polyethylene, meaning that if you put it under a microscope, it would look something like a chain-link fence but without all of the space between the links.

It can actually expand and then return automatically to its original shape, so it can accommodate the expansion that happens when water freezes. It brings hot water to a fixture quicker because it is laid out in either home-run systems from a main manifold or in sub-manifold systems designed to make the run from the water heater to the fixture as short as possible. Each room with hot water gets its own sub-manifold.

The other great thing about a sub-manifold system is that each manifold has its own shutoff, so you don’t have to shut off water to the entire house to work on one fixture or one room. These manifolds are similar to a circuit-breaker panel that carries electricity throughout your house. In these manifold systems, plumbers generally use red tubing for hot water runs and blue tubing for cold water, so it’s easy to identify source and temperature.

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One last advantage is that if you are handy and know plumbing, you can buy PEX at the local home-improvement store. However, one word of advice: Buy tubing and connections and crimping tools from the same manufacturer to guarantee compatibility and tight fittings. PEX manufacturers also make fittings that allow retrofit connections to copper pipe.

One thing you don’t want to do is bury PEX in contaminated soil. In fact, just for safety’s sake, keep all oil and grease away from PEX when you’re working with it, because some solvent-based compounds can work their way through the plastic and contaminate the water inside.

PEX started as tubing for radiant floor heat in Europe in the 1970s and moved to potable water delivery 30 years ago. It has withstood every test that plumbers put it through in those three decades, so more and more plumbers are comfortable using it. Ask your contractor or plumber if he is familiar with PEX, and discuss the possibilities for your home.

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