Lower record-based concern — Population-weighted indicator 91/100
State Overview
Water quality across Washington receives an overall grade of A (Lower record-based concern) with an average score of 91 out of 100, based on EPA compliance data from 316 ZIP codes statewide. This places Washington 16 points above the national average of 75, indicating relatively strong water quality management across the state. A majority of ZIP codes (62%) earn an A grade, reflecting strong compliance across most water systems. Scores are calculated from EPA Safe Drinking Water Information System (SDWIS) violation records, lead and copper testing results, PFAS monitoring data from UCMR5, and enforcement actions over the past 5 years.
Lowest Scoring ZIP Codes