Water Safety Score
IsWaterSafe's proprietary A-F grade for water systems, based on health violations (40%), contaminant exceedances (30%), enforcement history (20%), and monitoring compliance (10%).
How It Works
The Water Safety Score answers the question: "How safe is my tap water?" It combines four weighted factors derived from EPA Safe Drinking Water Information System (SDWIS) data. Health violations, the most serious type, indicating water that may pose an immediate health risk, carry the highest weight (40%). Contaminant exceedances that exceed MCLs carry 30% weight. A history of enforcement actions (indicating systematic problems) carries 20%. Monitoring violations, failing to test as required, carry 10% because they indicate potential hidden problems. A system with an "A" grade has no recent health violations, no contaminant exceedances, and a clean compliance record.
Related Terms
- Health-Based Violation, The most serious type of drinking water violation, indicating that water quality has exceeded a maximum contaminant level or failed to meet a treatment requirement that directly protects health.
- Maximum Contaminant Level (MCL), The highest level of a contaminant allowed in drinking water, set by the EPA and enforceable by law. Exceeding the MCL triggers a health-based violation.
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About This Definition
This definition is part of the IsWaterSafe Drinking Water Safety Glossary, 22 terms explaining water contaminants, treatment methods, and safety standards. Written for homeowners, renters, journalists, and public health professionals.