Understanding Water Quality Scores: A Complete Guide
WaterQ scores provide a quick way to compare drinking water quality across cities and states. This guide explains how scores work, what grades mean, and how to use them effectively.
Score Range and Meaning
WaterQ scores range from 0 to 100. The score reflects EPA-reported data on:
- Contaminant detection levels vs. EPA limits
- Violation frequency and severity
- Compliance history and recency
- Treatment technique effectiveness
Understanding Grades
Grades translate scores into easy-to-understand ratings:
- A (90-100): Excellent – minimal or no violations
- B (80-89): Good – minor issues, generally safe
- C (70-79): Fair – some violations, moderate concern
- D (60-69): Poor – recurring issues, higher risk
- F (0-59): Critical – significant violations, immediate attention needed
How to Use Scores
Scores work best as a starting point for deeper investigation. Here's a practical workflow:
- Compare cities – Use the city comparison tool to see side-by-side scores
- Check grades – Look at letter grades for quick risk assessment
- Review contaminants – Click into specific cities to see what contaminants were detected
- Check violations – Review violation history and status (resolved vs. ongoing)
Find Your City's Score
Browse scores by location:
What If Your Area Has a Low Score?
A low score doesn't necessarily mean unsafe water. Context matters:
- Monitoring violations – May not affect water safety
- Resolved issues – Past violations that have been fixed
- Treatment in place – Systems addressing specific contaminants
Always review the specific contaminant details and consider certified home testing for peace of mind.
Frequently Asked Questions
What is the WaterQ score range?
WaterQ scores range from 0 to 100. Higher scores indicate better water quality based on EPA compliance data, contaminant levels, and violation history.
What do WaterQ grades mean?
Grades range from A (90-100, excellent) to F (0-49, critical). Grades are derived from scores: A=90+, B=80-89, C=70-79, D=60-69, F=below 60.
How is the WaterQ score calculated?
Scores are calculated using EPA SDWIS data including contaminant detection levels, violation frequency and severity, compliance history, and recency of issues.
Can I trust a low score?
A low score reflects EPA-reported data. However, context matters—some violations may be monitoring-related rather than health-threatening. Always review specific contaminant details.