IAPMO recently reported in its I-Connection publication that a year-long study from the Civil and Environmental Engineering Department of Virginia Tech suggests that polyvinyl chloride (PVC) plastic pipes may create an environment for lead contamination.

The study found that chloramine, a chemical added by most public water systems to kill bacteria, can cause a chain reaction: the chloramine decays and forms ammonia, which in turn supports "autotrophic microbial nitrification." The nitrification process stimulates growth of heterotrophic bacteria (which grew easily in PVC pipe, but not in copper), which lowers the pH levels. Water with low pH (acidity), causes the corrosion of the brass fixtures and pipefitting common in plumbing systems.

The lead levels recorded exceed the EPA recommendations. The study is being published in the June issue of the American Chemical Society's Environmental Science & Technology journal. To view the report, click on the following link: http://pubs.acs.org/cgi-bin/sample.cgi/esthag/2008/42/i12/html/es702483d.html

Update: PPFA Responds

The Plastics Pipes and Fittings Association in the US has responded to a Plastics & Rubber Weekly (PRW.com) article, titled “Plastic pipes may indirectly pose ‘lead problem’,” published on 4 June, which referred to the above study published in the peer-reviewed Environmental Science & Technology.

In a letter, Dick Church, executive director of the PPFA, wrote:

“Plastic plumbing pipe contains no lead. Therefore, your recent story on “Plastic pipes may indirectly pose lead problem,” is a huge leap from any reality since it appears to blame lead extraction on the use of plastic pipe. In effect, the referenced experiment, partially funded by the Copper Development Association, created an artificial water world where water without disinfectant was used to farm bacteria in pipes by deliberately fertilizing the water with ammonium sulfate. In short and at best, the experiment does not represent real-world conditions. Its most dramatic shortcoming is its failure to recreate what actually happens in plumbing systems that are treated with chlorine, chloramines or may be disinfected in other ways.

“Another significant shortcoming of the experiment is its insufficient duration. Its conclusions are based on the absence of a bio-film on the copper after 200 days. A bio-film had formed on the plastic, lead and brass by that point, but not on the copper. According to Lehtola et al*, bio-film formation is a normal process common to all piping systems and equalizes just past 200 days. Since the copper itself is toxic to aquatic life, including the bacteria studied by this experiment, the water in the experiment’s copper systems maintains a higher (less acidic) pH than the water in plastic (CPVC), lead and brass systems. Hence, the bacteria enhancing nitrification had free reign in the test – in a normal plumbing system using chorine or chloramines, the bacteria would not develop, or, at least, would be kept in check. There’s no reason to believe water pH would normally change dramatically in the real-world as it apparently did in the experiment. The water pH is more likely to be highly variable due to the source of the water than the impact of the bacteria under any conditions.

“We hope everyone will keep in mind that the best way to avoid lead contamination in plumbing systems is to use products that do not contain lead. Blaming non-lead containing products for lead contamination just won’t cut it."

* Microbiology, chemistry and biofilm development in a pilot drinking water distribution system with copper and plastic pipes, Water Research 38 (2004) 3769-3779.