Disinfectants Cause Odorous Chemicals to Leach from Plastic Piping
Piping and distribution systems can have a direct effect on the taste, odor and quality of drinking water. While North America’s water supply may be more secure than other parts of the world, water quality threats are still present. Nearly two-thirds of water resource experts characterize America’s water situation as either at risk or already in crisis due to decaying infrastructure, lead in water threats, chemical contamination and more.
With millions of piping systems supplying businesses, homes and schools, researchers are looking at how piping materials may contribute to eroding water quality. A recent study by researchers from Virginia Tech looked at small-diameter piping systems inside buildings to determine if chemical leaching from the pipes affected the odor of drinking water. In addition, they examined whether the presence of disinfectants commonly used by water utilities amplified any issues.
The materials studied included one of the most common plastic choices on the market: cross-linked polyethylene (PEX). To simulate normal active conditions, an 8-foot PEX pipe was flushed for three hours, disinfected with 50 mg/L free chloride and then rinsed. After that, 10 research students and Virginia Tech faculty members assessed the odor of the water exiting the piping after three different flushing periods and using various levels of disinfectants. A summary of the results appears below.
Further analysis revealed that the unfavorable odors were caused by chemicals that had leached from the PEX pipe’s wall, such ethyl-tert-butyl ether (ETBE), a fuel additive used in the PEX manufacturing process. At its peak, ETBE levels exceeded 100 parts-per-billion (ppb), far above the 40 ppb limit regulated in some regions. Even following a third and final flush, the researchers found a “burning plastic” odor persisted.
While the odors generated were distasteful, ETBE’s effect on water quality was less conclusive. Some observations suggested ETBE broke down when exposed to disinfectants present in the water, but additional studies are needed to evaluate potential health risks or water quality threats. As stated by the research team, “In this era of heightened terrorism[,] understanding all potential sources of Taste and Odor (T&O) to drinking water is an important aspect of the Nation’s security… Consumers usually infer that if their water tastes and smells different it may not be safe. The presence of off-flavors or odors undermines consumer confidence in the drinking water industry resulting in increased consumption of bottled water or other alternative sources of water.”
If the water in your building is releasing any of these strong odors after traveling through PEX, the piping might be leaching chemicals into the water. For more information about chemical leaching and plastic piping, click here.