Illinois water quality
Illinois has 3,982 active public water systems (25,185 on file total), 1,752 of them graded by TapGraded.
Grade distribution
Biggest water systems
CHICAGO
CHICAGO, IL · 2,721,308 served
AURORA
AURORA, IL · 183,000 served
NAPERVILLE
NAPERVILLE, IL · 156,406 served
IL AMERICAN-CHAMPAIGN
GODFREY, IL · 150,000 served
ROCKFORD
ROCKFORD, IL · 147,051 served
IL AMERICAN-PEORIA
GODFREY, IL · 137,575 served
IL AMERICAN-EAST ST LOUIS
GODFREY, IL · 131,368 served
SPRINGFIELD
SPRINGFIELD, IL · 117,444 served
ELGIN
ELGIN, IL · 114,797 served
WAUKEGAN
WAUKEGAN, IL · 87,149 served
Lowest-graded systems
Active, graded systems serving at least 10,000 people, ordered by lowest Tap Grade first.
CALUMET CITY
CALUMET CITY, IL · 37,000 served
MAYWOOD
MAYWOOD, IL · 24,090 served
LOCKPORT
LOCKPORT, IL · 23,100 served
HOMEWOOD
HOMEWOOD, IL · 19,463 served
MACOMB
MACOMB, IL · 15,051 served
SOUTH ELGIN
SOUTH ELGIN, IL · 23,648 served
CARBONDALE
CARBONDALE, IL · 22,107 served
CREST HILL
CREST HILL, IL · 21,169 served
FOX LAKE
INGLESIDE, IL · 11,780 served
EAST PEORIA
EAST PEORIA, IL · 22,284 served
Cities in Illinois
Source: EPA SDWIS/ECHO · Data as of 2026Q2