Does PEX Piping Affect Drinking Water Quality?

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Plastic pipes generally are cheaper, lighter and easier to install than metal plumbing. So they’re the perfect choice for your home, right?

Not so fast.

Homeowners who installed a popular plastic pipe may want to filter water or flush their piping, say researchers studying cross-linked polyethylene piping, also called PEX pipe.

The product continues to grow in popularity because of its cheap cost and ease of use. But as more consumers turn to PEX piping, preliminary research shows PEX tubing may have a negative impact on water quality.

“Little is known about the degree to which plastic pipes sold in the U.S. affect drinking water quality,” says researcher Andrew Whelton, an assistant professor of civil engineering at Purdue University, in an article about his PEX piping research, which began when he was at the University of South Alabama.

Contaminants such as pesticides, oil, gasoline and benzene have a greater chance of permeating through PEX piping when compared to other types of piping, including copper, according to the research team. Contaminants from the pipes themselves also can leach into the water.

Potential PEX pipe problems

Researchers are examining the extent of PEX pipe’s impact on water quality by testing various brands of the plastic pipe.

Preliminary findings show different PEX brands affect water quality at different levels, and even pipes that pass safety tests may contain enough contaminants to affect water’s taste and smell, Whelton says.

“There really is tremendous variability across brands,” he adds. “Not all PEX pipe is created equal.”

The presence of drinking water odor can prompt homeowners to avoid their water altogether.

“A contractor who installed PEX in parts of a million-dollar home in Oklahoma asked us for help because the homeowners reported gasoline-like odors in a bathroom’s tap water,” Whelton says. “The homeowners refused to take showers in the PEX-plumbed bathroom because they were concerned about their health.”

By testing tap water from the home, Whelton’s team discovered that toluene, a solvent used for plastic resin synthesis was present above levels where odors would be detected. The level of solvent, however, did not exceed health standards.

The gasoline-smelling water, in this case, was safe to use.

Set of blue water pipes

It’s smart to know the type of water pipes used in your home. (Photo by Katelin Kinney)

Do water safety tests go far enough?

Mark Weilhammer, owner of Weilhammer Plumbing in Indianapolis, says contractors could benefit from information showing which brands of PEX piping affect water quality. He chose his PEX brand, AquaPEX, based on effectiveness and durability, he says, but he has no information about its impact on water quality .

Proponents of PEX, such as the Plastic Pipe and Fittings Association, state that PEX passes safety tests. For example, the nonprofit National Sanitation Foundation tests plumbing materials to determine if they leach certain chemicals within a 21-day period. The NSF looks for various contaminants including methanol and methyl tertiary ether, a gasoline additive that reduces carbon monoxide emissions.

PEX pipe meets the NSF standards, according to the Plastic Pipe and Fittings Association.

Whelton doesn’t disupte that, but his team found that contaminants affected water taste and odor, even in plastic water pipes that passed safety tests.

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It’s important to educate manufacturers and builders about the best options for making plastic pipes, with water quality foremost in mind, says Rebecca Bryant, study participant and managing prinicipal with Watershed LLC, a green-building consultant in Fairhope, Alabama.

“We’re really interested in broadening the discussion about indoor environmental quality,” Bryant says. “We deal a lot with the quality of indoor air, what chemicals are off-gassing into the air, if there’s any mold in the air, even thermal comfort and things like that. … There’s just not a real discussion about the quality of water provided.”

Lab researcher holding plastic pipe in water

Andrew Whelton, an assistant professor in civil engineering at Purdue, is leading research into the effects plastic pipes have on drinking water. (Photo courtesy of Purdue University/John Underwood)

How to prevent PEX water quality issues

A 2012 comparison showed PEX pipe was the least expensive among plastic pipes, costing 43 cents per foot compared to the most expensive metal, copper pipe, at $2.55 per foot. Because it requires less energy to produce than metal pipes, it’s become more common in homes and green building construction, according to Purdue.

Until researchers have definitive answers, Bryant says homeowners with existing PEX piping should filter drinking water from the tap.

Homeowners with PEX may also want to consider flushing their piping system on a regular basis. Contamination builds up as water stays stagnant in the piping, Whelton says.

To study the rate of contamination, his research team monitors standing water in PEX piping for three-day intervals.

“It would be like somebody going away on a Friday and coming back Sunday night,” he says. “What we’re finding is that during that three-day period, chemicals do build up in the water.”

The state of California requires contractors to flush PEX piping after installation, as part of a series of regulations meant to address concerns about its impact on water quality.

When installing PEX piping as part of new construction, contractors must flush the pipe system for at least 10 minutes, let the system stand for no less than one week and then flush the system long enough to empty the contained volume of water, according to the California Pipe Trades Council.

PEX pipe unknowns

PEX piping is still relatively new in the United States. Contractors began installing it about 30 years ago, with the state of California last to approve its use.

Some contractors hesitate to use PEX pipe until they know more about its long-term impact.

“We’re a re-piping company that’s installed copper for 40 some odd years, and we know about its reliability, whereas PEX is something that’s new to Santa Clara County,” says Jason Satalino, manager at Water Quality Plumbing in San Jose, California. “We’re not prone to using a product that may be able to make us some more money, but we’re not able to stand behind 100 percent.”