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"" It has been well documented that PEX pipes sold in Europe release chemicals into drinking water and alter odor quality. Two fairly limited scope studies were found that examined PEX pipes available in the USA, while a recent study has shown six brands sold in the USA can alter tap water chemical and odor quality for at least 30 days (Kelley et al. 2014). Other investigators found PEX pipes can alter drinking water chemical and odor quality (Durand & Dietrich 2007; Chemaxx 2007). Various types of PEX pipes (-a, -b, -c) exist and impart antioxidants and their degradation products, solvents used for resin production, manufacturing agents, and multiple unidentified organic contaminants into drinking water (Skjevrak et al. 2003; Koch 2004; Lund et al. 2011). Total organic carbon (TOC) concentration levels have been reported as high as 5 mg/L near room temperature after only 3 days of water contact (Koch 2004). Not all pipes released lesser levels of TOC at the end of the reported experiments. Some pipes released more TOC. For example, of 10 PEX brands tested in Europe for 9 days, five brands demonstrated a reduction in TOC after 9 days, two brands imparted more TOC, and three brands did not impart a detectable level of TOC at all during the studies (Skjevrak et al. 2003; Koch 2004). When European investigators examined multiple brands of PEX for 1 year, three of 11 brands imparted more TOC to tap water after 1 year than during the first 3 days installed (Lund et al. 2011). These dissimilar responses lend themselves to question what compounds are being released in what quantity and why?
Short-duration experiments have found PEX pipes available in Europe altered drinking water odor for up to a year (Skjevrak et al. 2003; Koch 2004; Lund et al. 2011). Some PEX pipes caused threshold odor number (TON) values ranging from 2 to 128 TON (Skjevrak et al. 2003; Koch 2004; Lund et al. 2011). In the USA, gasoline-like odor issues have been found in homes plumbed with new PEX-b piping; tert-butanol (TBA) and methyl tert-butyl ether (MTBE) were detected in drinking water at 52,000 μg/L and 740 μg/L, respectively (Chemaxx 2007). Ethyl tert-butyl ether (ETBE) concentrations from 23 μg/L to greater than 100 μg/L were found leaching from a single brand of new PEX pipe for a 9–12 day exposure period causing the water to smell similar to alcohol, burning, plastic, and chemical (Durand & Dietrich 2007). It is notable that each of the published PEX leaching studies utilized a different pipe cleaning method before conducting their leaching tests.
A factor not considered in any past laboratory or field investigation is whether or not the method used to clean the newly installed PEX pipe alters that material's leaching response. If the cleaning method alters the pipe's impact on water quality, results of published studies may not be directly comparable to one another and the field. In addition, plumbers who clean the pipes may in fact affect chemical leaching. The existing PEX pipe migration literature is based on the application of a number of different cleaning methods (i.e., National Sanitation Foundation International (NSFI) Standard 61, Utility Quick Test (UQT), European EN 1420 and EN 12873).
In the USA, pipes are cleaned according to the International Plumbing Code (IPC 2009) and state-specific plumbing codes. Differences between cleaning methods include variations in disinfectant concentration and contact time (Table 2). Flushing and disinfection steps aim to remove sediment from the system and kill pathogenic organisms. An exception however is the State of California Plumbing Code (CPC 2010) whereby all PEX plumbing systems must undergo a specific cleaning method before use. Discussions with several plumbers and building contractors from the Mobile, Alabama metropolitan area revealed that some new potable water plumbing pipes are simply flushed with tap water for 30 min before use and not disinfected. Thus, there appears to be a wide range of different plumbing pipe cleaning methods applied throughout the USA. Owing to this variation, several questions cannot be answered. (1) Does a longer stagnation period result in more chemical extraction from a new pipe or should more frequent fill/empty cycles be conducted to maximize chemical removal? (2) Does the chlorine disinfectant's presence or concentration affect pipe chemical leaching? To answer these questions, PEX pipe cleaning methods need to be compared to determine the effect they have on contact water quality. ""