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Compare drinking water quality across the United States. Select any state to view detailed city rankings, contaminant reports, EPA compliance data, and personalized filter recommendations based on local water quality issues.
Water quality varies dramatically across the United States due to differences in water sources, treatment infrastructure, environmental factors, and state regulations. Some states draw primarily from protected mountain reservoirs, while others rely on groundwater that may contain naturally occurring contaminants like arsenic or radium. Agricultural states often face nitrate contamination from fertilizer runoff, while industrial areas may have legacy pollution affecting water supplies.
Our state-by-state analysis is based on EPA Safe Drinking Water Information System (SDWIS) data, which tracks testing results and violations for all 150,000+ public water systems in the country. We also incorporate health guidelines from the Environmental Working Group (EWG) to identify contaminants that may pose risks even when below legal limits.
All water quality data is sourced from official government databases and leading environmental health organizations.
Learn about our methodologyOur water quality data comes directly from the EPA's Safe Drinking Water Information System (SDWIS) and ECHO databases. These contain testing results and compliance records for every public water system.
Water quality data is updated regularly as new testing results are reported to the EPA. Most water systems are required to test and report on a quarterly or annual basis.
States with consistently high water quality scores include Oregon, Colorado, and Massachusetts. These states benefit from protected water sources, strong environmental regulations, and well-maintained infrastructure. However, water quality varies significantly within each state, so it's important to check your specific city's report.
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