Fair — Average Score 74/100
State Overview
Water quality across Illinois receives an overall grade of C (Fair) with an average score of 74 out of 100, based on EPA compliance data from 1259 ZIP codes statewide. This is roughly in line with the national average of 75. Approximately 13% of ZIP codes (169 areas) receive a D or F grade, indicating communities with notable water quality concerns that warrant attention. The lowest-scoring area is ZIP code 61350 (Ottawa) with a score of 25/100. 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