Drinking water odors, chemicals above health standards caused by 'green building' plumbing

October 20, 2014  

Whelton pipes

Andrew Whelton, an assistant professor in Purdue's Lyles School of Civil Engineering and Division of Environmental and Ecological Engineering, is leading research into the effects plastic pipes have on drinking water in eco-friendly green buildings in the United States. (Purdue University photo/John Underwood)
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WEST LAFAYETTE, Ind. – Several types of plastic pipes in eco-friendly green buildings in the United States have been found to leach chemicals into drinking water that can cause odors and sometimes exist at levels that may exceed health standards.

Buildings are being plumbed with many types of plastic drinking water pipes. These include crosslinked polyethylene (PEX), high-density polyethylene (HDPE), polyvinylchloride (PVC), chlorinated PVC (cPVC) and polypropylene (PP) pipes, said Andrew Whelton, an assistant professor in Purdue University's Lyles School of Civil Engineering and Division of Environmental and Ecological Engineering.

Plastic pipes are generally less expensive, lighter and easier to install than metal pipes. 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. 

Thousands of dollars can be saved during construction by installing plastic instead of metal plumbing systems, and proponents assert plastic pipes require less energy to manufacture - generating less carbon dioxide compared to metal pipes - ostensibly making them a good fit for green buildings.

“Little is known about the degree to which plastic pipes sold in the U.S. affect drinking water quality,” Whelton said.

He will detail research findings in a presentation during the 2014 U.S. Green Building Council’s Greenbuild International Conference & Exposition on Friday (Oct. 24) in New Orleans with Rebecca Bryant, managing principal of Watershed LLC of Fairhope, Alabama. Some testing results were published online in September in the journal Water Research. There, the researchers describe drinking water impacts caused by six brands of PEX pipes available in the United States.

In the September study, drinking water was tested from a PEX plumbing system in a “net-zero energy” building in Maryland six months after the system had been installed. The testing revealed the presence of 11 chemicals that were PEX pipe ingredients and ingredient degradation products. Research with PEX pipes in the laboratory also showed that six brands caused drinking water to exceed the U.S. Environmental Protection Agency's maximum recommended drinking water odor limit, Whelton said. The U.S. EPA's maximum drinking water odor limit is a "threshold odor number" of 3, or 3 TON. Compliance is voluntary because the standard is based on aesthetic - not health - considerations.

Odor and chemical levels were monitored with and without chlorine treatment over a 30-day period for the six pipe brands. Chlorine, the most popular disinfectant chemical used in the United States, protects drinking water from disease-causing organisms as it travels to the tap. When chlorine reacted with chemicals leached by the plastic pipes, odor levels for one brand of PEX pipe tripled. While the total mass of chemicals leached by PEX pipes was found to decline after 30 days of testing, odors generally continued as the pipes aged, Whelton said.

A general assumption in the United States is that chemicals responsible for drinking water odors pose no health dangers. Although, several chemicals found in the plumbing research have regulated health limits, and one PEX pipe brand caused drinking water to exceed the ethyl-tert-butyl ether (ETBE) drinking water health standard. ETBE is a PEX pipe manufacturing byproduct with drinking water standards in New Hampshire and New York state.

When establishing the ETBE limit in New Hampshire, public health officials specifically added a 10-fold reduction to allow for its suspected carcinogenic potential. However, no federal drinking water standard exists, Whelton said.

The researchers found ETBE drinking water levels as high as 175 parts per billion (ppb) during the first three days of PEX pipe use and then 74 ppb after 30 days of use when the testing ended. New Hampshire has the most stringent drinking water health standard of 40 ppb. Michigan also has an ETBE standard, but it is based on limiting drinking water odor caused by ETBE.

The presence of drinking water odor can prompt homeowners to avoid their drinking 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 said. "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 and ETBE were present above levels where odors would be detected. Neither toluene nor ETBE exceeded health standards, however. The gasoline smelling water was safe to use.

The research, funded by the National Science Foundation, also is showing that there are differences in the quality of PEX products on the market, and different brands cause different odor and chemical-leaching impacts.

The Water Research paper was authored by University of South Alabama graduate student Keven M. Kelley; associate professor Alexandra C. Stenson and assistant professor Rajarashi Dey at the University of South Alabama; and Whelton, a former faculty member at the University of South Alabama.

The team plans to continue the work and release additional results from the study over the next several months. Findings show some chemicals released by plumbing pipes can be transformed into carcinogenic chemicals regulated by the EPA; chemicals leached by certain plastics are conducive to bacterial growth; and plumbing system cleaning practices described in some, but not all, plumbing codes can cause PEX pipe chemical leaching to worsen.

The work is funded by an NSF grant entitled "Towards a Safer and Greener Indoor Environment: Chemical Liberation from Polyethylene Plumbing Pipe." 

Writer: Emil Venere, 765-494-4709, venere@purdue.edu 

Source: Andrew J. Whelton, (765) 494-2160, awhelton@purdue.edu


Release of Drinking Water Contaminants and Odor Impacts Caused by Green Building Cross-linked Polyethylene (PEX) Plumbing Systems

Keven M. Kelley 1, Alexandra C. Stenson 2, Rajarashi Dey 3, Andrew J. Whelton 4,*

1 Department of Civil Engineering, University of South Alabama

2 Department of Chemistry, University of South Alabama

3 Department of Statistics and Mathematics, University of South Alabama

4 Lyles School of Civil Engineering, Environmental and Ecological Engineering, Purdue University

* Corresponding author. Department of Civil Engineering, 550 Stadium Mall Drive West Lafayette, IN 47907, USA. Tel.: þ1 765 496 3996. E-mail addresses: ajwhelton@gmail.com, awhelton@purdue.edu (A.J. Whelton).

Green buildings are increasingly being plumbed with cross-linked polyethylene (PEX) potable water pipe. Tap water quality was investigated at a six-month-old plumbing system and chemical and odor quality impacts of six PEX pipe brands were examined. Eleven PEX-related contaminants were found in the plumbing system; one regulated (toluene) and several unregulated: Antioxidant degradation products, resin solvents, initiator degradation products, or manufacturing aides. Water chemical and odor quality was monitored for new PEX-a, -b and -c pipes with (2 mg/L free chlorine) and without disinfectant over 30 days. Odor and total organic carbon (TOC) levels decreased for all pipes, but odor remained greater than the USA's Environmental Protection Agency's (USEPA) secondary maximum contaminant level. Odors were not attributed to known odorants ethyl-tert-butyl ether (ETBE) or methyl-tert-butyl ether (MTBE). Free chlorine caused odor levels for PEX-a1 pipe to increase from 26 to 75 threshold odor number (TON) on day 3 and affected the rate at which TOC changed for each brand over 30 days. As TOC decreased, the ultraviolet absorbance at 254 nm increased. Pipes consumed as much as 0.5 mg/L as Cl2 during each 3-day stagnation period. Sixteen organic chemicals were identified, including toluene, pyridine, methylene trichloroacetate and 2,4-di-tert-butylphenol. Some were also detected during the plumbing system field investigation. Six brands of PEX pipes sold in the USA and a PEX-a green building plumbing system impacted chemical and drinking water odor quality.

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