20th October 2014
Andrew Whelton, Assistant Professor at Purdue’s Lyles School of Civil Engineering and Environmental and Ecological Engineering Department, is a leader in research into the impact of plastic pipes on drinking water in green buildings in the United States. (Purdue University Photo / John Underwood)
WEST LAFAYETTE, Ind. – Various types of plastic pipe in environmentally friendly green buildings in the United States have been found to leach chemicals into drinking water that can cause odors and are sometimes in amounts that potentially exceed health standards.
Buildings are fitted with many types of plastic drinking water pipes. These include crosslinked polyethylene (PEX), high density polyethylene (HDPE), polyvinyl chloride (PVC), chlorinated PVC (cPVC), and polypropylene (PP) pipes, said Andrew Whelton, assistant professor at Purdue University’s Lyles School of Civil Engineering and Division for environmental and eco technology.
Plastic pipes are generally cheaper, lighter and easier to install than metal pipes. A 2012 comparison found that PEX pipe was cheapest among plastic pipes at 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 claim that plastic pipes require less energy to manufacture – compared to metal pipes produce less carbon dioxide – and they are supposedly good for environmentally friendly buildings.
“Little is known about the extent to which plastic pipe sold in the US affects drinking water quality,” Whelton said.
He will explain the research in a presentation at the US Green Building Council’s 2014 Greenbuild International Conference & Exposition on Friday, October 24th in New Orleans with Rebecca Bryant, Managing Director of Watershed LLC of Fairhope, Alabama. Some test results were published online in the journal Water Research in September. There, the researchers describe the effects of drinking water caused by six brands of PEX pipe available in the USA.
The September study tested six months after the installation of drinking water from a PEX plumbing system in a “Net Zero Energy” building in Maryland. The tests revealed the presence of 11 chemicals which were PEX pipe components and degradation products. Research on PEX pipes in the lab also showed that six brands caused drinking water to exceed the maximum limit for drinking water odor recommended by the U.S. Environmental Protection Agency, Whelton said. The US EPA’s maximum drinking water odor limit is an “odor threshold number” of 3 or 3 TON. Compliance is voluntary as the standard is based on aesthetic and not health considerations.
The odor and chemical values were monitored with and without chlorine treatment over a period of 30 days for the six pipe brands. Chlorine, the most popular disinfectant chemical in the US, protects drinking water from disease-causing organisms on its way to the tap. When chlorine reacted with chemicals leached through the plastic pipes, the odor levels tripled for a brand of PEX pipe. While the total mass of chemicals leached through PEX pipes decreased after 30 days of testing, the odors generally persisted as the pipes age, Whelton said.
In the United States, it is generally accepted that chemicals that cause drinking water odors are not a health hazard. Although several chemicals found in sanitary research have regulated health limits and a PEX pipe brand caused the drinking water to exceed the health standard for ethyl tertiary butyl ether (ETBE). ETBE is a by-product of PEX pipe manufacturing with drinking water standards in New Hampshire and New York State.
When setting the ETBE limit in New Hampshire, health officials specifically added a 10x reduction to account for its suspected carcinogenic potential. There is no federal drinking water standard, however, Whelton said.
The researchers found that the ETBE drinking water level was up to 175 ppm for the first three days of using PEX pipes and 74 ppb after 30 days after the tests were completed. New Hampshire has the strictest drinking water health standard of 40 ppb. Michigan also has an ETBE standard, but it is based on limiting the smell of drinking water caused by ETBE.
The presence of drinking water odor can lead homeowners to shun their drinking water altogether.
“A contractor who installed PEX on parts of a million dollar home in Oklahoma asked for help after homeowners reported gasoline-like smells in bathroom tap water,” Whelton said. “The homeowners refused to shower in the PEX bathroom because they were worried about their health.”
While testing tap water from the house, Whelton’s team discovered that toluene, a solvent used in plastic resin synthesis, and ETBE, were present above levels at which odor was detected. However, neither toluene nor ETBE exceeded health standards. The water smelling of gasoline was safe to use.
The study, funded by the National Science Foundation, also shows that there are differences in the quality of PEX products on the market, and different brands have different effects on odor and chemical leaching.
The water research paper was written by Keven M. Kelley, a PhD student at the University of South Alabama. 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 work and publish more results from the study in the next few months. The results show that some chemicals released from pipelines can be converted into carcinogenic chemicals, which are regulated by the EPA. Chemicals leached from certain plastics encourage bacterial growth. The installation system cleaning procedures described in some, but not all installation codes, can degrade the chemical leaching of PEX pipes.
The work is funded by an NSF grant entitled “Towards a Safer, Greener Indoor Climate: Chemical Exemption from Polyethylene Pipelines”.
Writer: Emil Venere, 765-494-4709, [email protected]
Source: Andrew J. Whelton, (765) 494-2160, [email protected]
Release of drinking water pollution and unpleasant odors through environmentally friendly installation systems made of cross-linked polyethylene (PEX)
Keven M. Kelley 1, Alexandra C. Stenson 2, Rajarashi Dey 3, Andrew J. Whelton 4, *
1 Faculty 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. Email addresses: [email protected], [email protected] (AJ Whelton).
Green buildings are increasingly being laid with drinking water pipes made of cross-linked polyethylene (PEX). Tap water quality was examined on a six month old plumbing system and the effects of six brands of PEX pipe on chemical and odor quality 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 aids. The water chemistry and odor quality was monitored for 30 days on new PEX a, b and c pipes with (2 mg / l free chlorine) and without disinfectants. The odor and total organic carbon (TOC) decreased on all pipes, but the odor remained higher than the United States Environmental Protection Agency (USEPA) Secondary Maximum Pollutant Content. Odors were not attributed to the known odorous substances ethyl tert-butyl ether (ETBE) or methyl tert-butyl ether (MTBE). Free chlorine caused odor levels for PEX-a1 pipes to increase from 26 to 75 (TON) on day 3 and affected the rate at which the TOC changed for each brand over 30 days. The UV absorption at 254 nm increased with decreasing TOC. Pipes consumed up to 0.5 mg / L Cl2 during each 3-day stagnation period. 16 organic chemicals were identified, including toluene, pyridine, methylene trichloroacetate, and 2,4-di-tert-butylphenol. Some were also discovered during the field survey of the plumbing system. Six brands of PEX pipe sold in the US and a PEX plumbing system for green buildings affected the odor quality of chemicals and drinking water.