Drinking Water Report Card Methodology

WaterViolations.org report cards summarize EPA Safe Drinking Water Information System (SDWIS) records into a Drinking Water Violation Exposure Score. The score helps reporters, researchers, and residents identify places where drinking-water compliance questions may deserve closer local follow-up.

Important: this is not an official government grade and it is not a direct tap-water safety test. Violation records can lag current conditions, and consumers should contact their utility or state drinking-water agency for official notices and current guidance.

County report cards start at 100 points and subtract two weighted penalties:

• Health-based violations per 100,000 people served — capped at 60 points. Penalty: min(60, rate × 12).
• Active health violation system rate — capped at 40 points. Penalty: min(40, active rate × 200).

Final score = 100 minus penalties, rounded and capped between 0 and 100. Letter bands are: A 90–100, B 80–89, C 70–79, D 60–69, F below 60.

• Health-based violation: a violation tied to contaminant levels or required treatment standards that may affect health.
• Active health violation: a water system with at least one health-based violation listed as unresolved in the local data.
• Population served: the population value reported for each public water system in SDWIS.

Use report cards as a story-finding and screening tool. Good local follow-up questions include: What contaminant caused the violation? Has the utility issued a public notice? Is the violation resolved? Are vulnerable groups affected? What does the latest Consumer Confidence Report say?

View weakest county scores, download county scores as CSV, or open journalist resources.