Increasing Chloride Levels in U.S. Rivers Can Lead to Increased Corrosion in Water Pipes


A new study by the U.S. Geologic Survey (USGS) found increasing chloride levels in many U.S. rivers, which contributes to increased corrosion in water distribution pipes. Over a 20-year period, from 1992-2012, chloride concentrations increased as well as other measures of the potential corrosivity of water such as chloride-sulfate mass ratio (CSMR) and the Larson Ratio (LR).  The study also analyzed the current status (2010-2015) of chloride, CSMR, and LR. The long-term found slight increases in chloride, CSMR, and LR across the U.S., but found much larger increases in urban-dominated sampling sites.  Urbanization was strongly correlated with elevated chloride, CSMR, and LR, most likely due to the use of road salt in the snow-affected areas of the study.
Elevated chloride, CSMR, and LR in source waters can result in increased corrosion in water pipes and lead action level exceedances (ALEs) under the Lead and Copper Rule (LCR). In this study, the probability of lead ALEs in drinking water systems increased along with raw surface water CSMR, indicating a statistical connection between surface water chemistry and corrosion in water pipes. Research on this connection between increased CSMR and increased corrosion in water pipes started a decade ago with research conducted at Virginia Tech, and continues to be an important consideration for LCR compliance.