Plastic Water Piping Leads to Greater Corrosion, Lead Levels

Despite the reduced use of metals in potable-water piping systems using plastic pipe such as PEX and CPVC, recent research has found that the bacterial environments in those pipes can lead to higher content of metals, including lead, than in systems using copper pipe.

Environmental Science & Technology examined interactions among several variables: pipes of various kinds, water treated with chloramine (commonly used by water utilities as an alternative to chlorine), pH, phosphates (often added to water as an anti-corrosive), and nitrifying bacteria. While most water-test protocols involve flushing pipes before collecting a sample, the researchers studied stagnant “first draw” water that had been sitting in pipes. They found that the greater inertness of plastic pipe allows nitrifying bacteria to create more acidic conditions, which in turn leach more lead, copper, and zinc from brass fittings and fixtures.

That leaching created lead contamination exceeding U.S. Environmental Protection Agency standards, as well as potentially causing premature failure of fittings. Copper pipe inhibits those same bacteria, resulting in less leaching. While the findings might be a reason to avoid plastic piping, or at least run the water before using it, the researchers declined to make firm recommendations.