A recent U.S. Geological Survey assessment of more than 20,000 wells nationwide indicates that groundwater found in 25 states and the District of Columbia has a high potential for being naturally corrosive.
The findings have the greatest implications for homeowners with private drinking water systems. Naturally corrosive water is not dangerous to consume by itself. Nevertheless, it can cause health-related problems by reacting with pipes and plumbing fixtures in homes. If plumbing materials contain lead or copper, these metals may be leached into the water supply by corrosive water. Signs of corrosive water causing leaching of metals may include bluish-green stains in sinks, metallic taste to water, and small leaks in plumbing fixtures.
Two indicators were used to assess the potential corrosivity of groundwater. The first index is the Langelier Saturation Index, an indicator of whether mineral scale may form on the inside of pipes and prevent the release of lead to drinking water. The second indicator, the chloride-to-sulfate ratio, measures the potential of source water to promote the release of lead in pipes through galvanic corrosion.
These two indicators were combined into one indicator to assess the prevalence of potentially corrosive groundwater nationwide.