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Civil Engineering Magazine THE MAGAZINE OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS

Plastic Pipes for Drinking Water Come under Scrutiny

By Catherine A. Cardno, Ph.D.

Researchers who have discovered that the plastic plumbing regularly used in "green" buildings can contaminate drinking water argue for changes in building industry practices.

 

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Researchers are studying the effect of plastic pipelines on the quality and odor of drinking water that has been treated with a variety of chemicals. Wikimedia Commons/Mark Schellhase

November 13, 2014—Americans are familiar with local and regional variations in the quality of their water supply. What is not part of the typical conversation, however, is the impact that the plastic or metal pipes used within individual buildings have on drinking water quality. Researchers at Purdue University and the University of South Alabama have established the significance of just that with their research-based discovery that certain types of plastic pipes that are gaining traction in the marketplace can contaminate some types of drinking water. 

Using those findings, the research team is advocating for the so-called green building industry to "broaden its approach to indoor environmental quality and encompass all of the ways that material selection, building design, and building operations can impact [a] premise's water quality," says Andrew Whelton, A.M.ASCE, an assistant professor of civil, environmental, and ecological engineering at Purdue University. 

Whelton is overseeing a multiyear examination of the effects that plastic piping has on drinking water quality. He is working with Alexandra Stenson, Ph.D., an associate professor of chemistry at the University of South Alabama, and Rebecca Dunn Bryant, AIA, LEED-AP, GGP, the principal of the Fairhope, Alabama-based green-building design and consulting company Watershed. 

Traditionally, metal pipes have been used for plumbing systems within the United States. However, the comparatively low price of plastic piping has driven its widespread use in homes and commercial buildings, according to Bryant. The use of plastic pipes has become so common, Whelton says, that "water companies are even choosing to use plastics in parts of their buried water piping networks." 

To date, few studies have been conducted on plastic drinking water pipes sold in the United States, according to Whelton, and the results of those few studies are rarely made public. While tests on plastic piping's effect on drinking water have been completed in Europe and Asia, Whelton notes that those results are not applicable in the United States because its plastic piping is manufactured differently. For this reason, his research team is studying which types of chemicals leach from various types and brands of plastic pipes and whether those chemicals exceed health or aesthetic standards, transform into other compounds due to interactions with water disinfectants, and whether those leached chemicals promote microbiological growth inside plumbing systems. The results will be made public.

Under the National Sanitation Foundation International's Standard 61: Drinking Water System Components-Health Effects , tests are conducted on many plumbing pipes before they are sold to "determine what contaminants may migrate or leach from the product into drinking water," according to Whelton. The tests "also confirm if they are below the maximum levels allowed to be considered safe," he says. But the results aren't made public.

According to a surveyof U.S. state drinking water agencies released in 2013 by the National Sanitation Foundation International (NSF) in cooperation with the Association of State Drinking Water Administrators (ASDWA), "48 states have legislation, regulations, or policies requiring drinking water system components to comply with, or be certified to NSF/ANSI Standard 61."

Whelton points out, however, that the Standard 61 test does not address several important issues. "The test assumes water will not be used from newly installed pipes for 14 days," he says. "Secondly, the test involves only one type of [drinking water] disinfectant, [but] several other chemicals are used to keep water safe inside plumbing systems across the U.S." Other acceptable drinking water disinfectants include chloramine, also known as combined chlorine, as well as potassium permanganate and chlorine dioxide, according to Whelton. Whelton also points out that certain states have more stringent drinking water standards than what Standard 61 considers.

"Standard 61 also does not address drinking water odor, which is important to consumers," Whelton says. "The takeaway point is that many pipes that are available for construction professionals to install do not undergo testing that represents the field," he says. Because of these issues, additional research is necessary to determine how plastic pipes will behave once installed, he says.

Whelton's team has already tested how various brands of plastic pipe affect water-chemical quality and odor, most of their effort focused on cross-linked polyethylene, or PEX, plastic piping. And his results show high variability between how different brands of PEX pipe perform with respect to the number and amount of chemicals that they release into drinking water. "Some manufacturers make a fairly 'clean' product and other manufacturers make a very 'dirty' product," he says. "There is wide variability across available brands in the U.S. and there are at least three different PEX manufacturing processes."

Bryant agrees. "The variability in chemical leaching from brand to brand is extremely significant," Bryant notes. "If consumers had access to information about leaching per brand, then market forces would do the work to clean up manufacturing processes and the products," she says. 

Bryant also notes the research team's findings that "many chemicals that end up in your water may not be material 'ingredients' per se." They may be reactants between material ingredients or between water and disinfectants, or they may be by-products of the manufacturing process. "This tells us that while the disclosure of material ingredients… is an important first step, it does not fully capture the impact of piping or other water-contact materials on water quality," she says. (The newest edition of the U.S. Green Building Council's Leadership in Energy and Environmental Design [LEED] rating system requires this type of disclosure, Bryant points out).

When the researchers examined drinking water piped through eight brands of PEX pipe, they found ethyl- tert -butyl ether (ETBE), which is a chemical that is produced as a by-product of PEX pipe manufacturing, according to Whelton. Even though there are no federal guidelines on safe levels of ETBE, "certain states have decided to impose their own limits," Whelton notes. The levels of ETBE discovered by the researchers in the pipes exceeded the health limits established by both New Hampshire and New York, he says. "That's an important finding because to my knowledge, the pipes that are being sold and marketed today are not marketed for different states." Most are promoted as having been tested by the NSF's Standard 61, but this method does not test for ETBE, he points out.

Whelton and his team also tested the plastic pipes for odor over the course of a 30-day period. "We found that on day 30, odor levels were equal to or less than those on day 3, but all pipes exceeded the EPA's recommended drinking water odor level," he noted. "Odor is an aesthetic standard, it's not a health-based standard," Whelton points out. "But …water companies across the United States strive to provide clean, safe, and pleasing water to people…[and] the data we have show building plumbing piping can drastically change the quality of that water."

Bryant, Whelton, and Stenson have drafted a pilot credit for the LEED rating program. The requirement that manufacturers disclose the ingredients of their building products "is the backbone" of the credit, Bryant says. "The credit goes a step further, requiring disclosure of the NSF Standard 61 extraction reports, which analyze compounds in water that have been in contact with these pipes," Bryant says. "The credit also includes specific considerations for preventing lead contamination in metal piping, and addresses best practices to prevent pathogen proliferation in all piping types." 

"Many green building organizations and the USGBC in particular, have been quite embattled as they try to promote consumers' right to know more about the materials in their buildings," Bryant says. "The discussion has been likened to the first debates around nutritional labeling for food products. In those debates, manufacturers argued that disclosure would ruin their businesses, that competitors would steal their 'secret recipes,' etc. It's very similar to the discussion we're having today about building materials.

"Plumbing piping is basically food packaging, and it needs to receive an appropriate level of scrutiny as such," Bryant says.

Future research will continue to study flushing and disinfection techniques in various types of piping, and will include an examination of how water temperature affects the leaching process.

The results of the first study released by the research group are available online.

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