Good — Average Score 81/100
State Overview
Water quality across California receives an overall grade of B (Good) with an average score of 81 out of 100, based on EPA compliance data from 1716 ZIP codes statewide. This places California 6 points above the national average of 75, indicating relatively strong water quality management across the state. A majority of ZIP codes (54%) earn an A grade, reflecting strong compliance across most water systems. The lowest-scoring area is ZIP code 91791 (West Covina) with a score of 15/100. 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