Sonoma County Water Quality

Sonoma County, California has a water quality grade of D with a score of 45.1/100, based on EPA Safe Drinking Water Information System data. The county has 104 health-based drinking water violations on record.

Sonoma County has 104 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.

Sonoma County's water quality score of 45.1/100 is higher than the California state average of 44.6. The average water quality grade across California is D, based on data from 58 counties with available water quality data.

Based on EPA data, Sonoma County has a water quality grade of D (45.1/100). This indicates below-average water quality with significant compliance issues. Residents may want to consider home water filtration. For the most up-to-date information, contact your local water utility or review your Consumer Confidence Report (CCR).

Sonoma County has 104 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.

Sonoma County ranks #30 out of 58 counties in California by water quality score (1 = best). With a score of 45.1/100, it falls in the middle third of counties statewide. Rankings are based on EPA Safe Drinking Water Information System (SDWIS) data including health-based violations and compliance records.