BLACKSBURG, VA. -- The Civil and Environmental Engineering Department of Virginia Tech recently conducted a sensory impact study on various piping materials in regard to the possible leaching of polymer additives, organic compounds and oxidation of the surface of the pipe during extrusion – all of which can affect the taste and smell of the water.
The study by the engineering school at Virginia Tech, formally known as Virginia Polytechnic Institute and State University, was paid for by a grant from the National Science Foundation. The study's conclusions were presented at a meeting of the American Chemical Society in Boston last August.
The study concluded that CPVC is the preferred choice from a taste and smell viewpoint, as well the absorption of disinfectants used in the water treatment process.
In recent years, polymer pipes have gained market share particularly in residential but also in commercial applications because of their superior performance in all of these areas.
One questionable area regarding the use of polymer materials, however, has been the possible introduction of perceptible tastes and odors that either occur during the extrusion process or during the pipe’s interaction with various water treatment disinfectants. The study confirmed that not all plastics produce the same results with regard to the possible leaching of polymer additives, organic compounds and oxidation of the surface of the pipe during extrusion.
Specifically, CPVC performed consistently higher when compared to copper, high-density polyethylene (HDPE), epoxy lining and the PEX piping selected for the study.
In fact according to the report, “Results indicate that copper pipe consumed nearly all the residual disinfectants… results for the polymer materials indicated that CPVC imparted the fewest organic compounds to the water, consumed the least amount of disinfectants, and produced no noticeable odors. All other polymer materials imparted distinct odors and organic chemicals to water and consumed residual disinfectant.”
The Virginia Tech study is not the first to examine the sensory impacts from polymer pipes interacting with drinking water oxidants. This study, however, compared both chemical and consumer-assessed sensory characteristics of water in contact with the materials. A trained human panel used Flavor Profile Analysis to assess odors. A chemical process commonly referred to as SPME-GC-MS (or more formally known as solid phase microextraction-gas chromatography-mass spectrometry), which utilizes various fiber elements to extract compounds in the water, was used to detect and identify organic components. Total organic carbon was determined using an automated Sievers 800 Portable TOC Analyzer.
The test was designed to accomplish two objectives: 1) to investigate the sensory properties of water with either chlorine or chloramines when it came into contact with different piping materials; 2) to investigate changes in residual disinfectant and leaching of organic chemicals from pipe when in contact with drinking water.
While some materials performed well in certain categories, they under-performed in others. The best-performing PEX pipe, for example, leached the greatest amount of organic carbon, as well as the greatest number of volatile organic compounds, but did not contribute the most intense odors (although it did contribute a variety of odors). HDPE leached only a minor amount of organic carbon (but many specific organics) yet imparted the greatest odor intensity.