Cook County Water Quality

Cook County, Illinois has a water quality grade of A with a score of 70.8/100, based on EPA Safe Drinking Water Information System data. The county has 30 health-based drinking water violations on record.

Cook County has 30 health-based drinking water violations recorded by the EPA. Health-based violations indicate instances where contaminant levels exceeded EPA Maximum Contaminant Levels (MCLs). Violations may have been resolved — check with your local water utility for current status.

Cook County's water quality score of 70.8/100 is higher than the Illinois state average of 47.8. The average water quality grade across Illinois is D, based on data from 102 counties with available water quality data.

Based on EPA data, Cook County has a water quality grade of A (70.8/100). This indicates good to excellent water quality with strong compliance. For the most up-to-date information, contact your local water utility or review your Consumer Confidence Report (CCR).

Cook County has 30 health-based drinking water violations on record from the EPA SDWIS database. A higher violation count can result from aging infrastructure, underfunded water utilities, agricultural runoff contamination, or industrial pollution. Counties with more water systems may also see more violations simply due to scale. Residents concerned about water quality should consider independent water testing and home filtration systems.

Cook County ranks #15 out of 102 counties in Illinois by water quality score (1 = best). With a score of 70.8/100, it falls in the top third of counties statewide. Rankings are based on EPA Safe Drinking Water Information System (SDWIS) data including health-based violations and compliance records.