Illinois
About 90% of the population served by community water systems in Illinois had no recent health-based violation. The score reflects EPA drinking-water compliance, weighted by how many people each system serves.
How Illinois’s score works
We pull every active community water system in Illinois from the EPA’s Safe Drinking Water Information System, then find those with a health-based violation in the last five years. The score is the share of the state’s water-system population served by systems without such a violation. City-level detail — utility, lead levels, and specific contaminants — is coming next.
Full methodology · Compliance snapshot, not a live reading. A system meeting federal standards can still carry risk (e.g. lead from home service lines). Not medical advice.