TapWaterMap shows US tap-water quality city by city, using the EPA's own Safe Drinking Water Information System (SDWIS) records. Look up the water systems serving a city, the contaminants and violations on record — with dates and whether the EPA classifies each as health-based — compare cities side by side, and understand what any contaminant is. It's calm and sourced: it reports what the EPA recorded and never gives a safety verdict. Covers about 19,000 cities across all 50 states and DC.