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.