States › Illinois

Illinois Tap Water Quality 2026

EPA drinking water data for 1,297 cities across Illinois — covering lead levels, violation history, and compliance status.

Systems tracked: 1,115 Cities covered: 1,297 Updated: 2026 Q2
B

Illinois earns a B for overall water quality

1297 communities across 102 counties and 1115 water systems. 94.3% have no open violations.

Median lead where detected: 2.80 ppb
55.1% of systems report lead as not detected — a state filing convention, not a water quality measure
PFAS tested at 41.0% of communities; 22 above the federal limit
Lead reported for 100.0% of communities
94.3% of communities have no open violations
Water Systems
1,115
Active community systems
Median Lead Level
2.8 ppb
19% of EPA action level
Fully Compliant
94.3%
of systems — no active violations
How we grade states Grades are based on actual EPA enforcement data — MCL violations and lead levels measured against the 15 ppb federal action level. We do not use MCLG-based detections, which are aspirational zero-tolerance goals that would make nearly every state look dangerous. Read our full methodology →

Best & Worst Cities in Illinois

✓ Cleanest Water
Third Lake
Lake County
0.0 ppb A
Springfield
Sangamon County
0.0 ppb A
Champaign
Champaign County
1.0 ppb A
Bloomington
McLean County
0.6 ppb A
Bolingbrook
Will County
0.0 ppb A
Decatur
Macon County
2.6 ppb A
⚠ Needs Attention
Danforth
Iroquois County
0.0 ppb F
Secor
Woodford County
1.2 ppb F
Windsor
Mercer County
6.2 ppb F
Crest Hill
Will County
1.2 ppb F
Albany
Whiteside County
2.2 ppb F
St. Rose
Clinton County
0.0 ppb F

Water Quality by County

102 of 102
Sort:
CountySystemsLead LevelViolationsGrade
Cook County 119 5.5 ppb 0 B
Lake County 56 6.3 ppb 0 B
Will County 38 1.7 ppb 0 B
Madison County 31 1.9 ppb 0 B
DuPage County 30 1.5 ppb 0 B
LaSalle County 26 2.1 ppb 0 B
Champaign County 26 1.0 ppb 0 B
Macoupin County 25 2.0 ppb 0 B
McHenry County 25 1.8 ppb 0 B
St. Clair County 24 3.0 ppb 0 B

About Illinois Drinking Water

Illinois is served by 1115 community water systems covering 1297 communities across 102 counties. 94.3% have no open violation on record.

Lead was detected in 582 communities, with a median of 2.80 ppb — 19% of the federal action level. A further 715 reported none detected. That share is a state reporting convention rather than a measure of water quality, so it is stated separately rather than averaged in.

PFAS has been tested at 41.0% of communities here, and 22 are above the limits EPA set in 2024. Coverage matters: states that test more find more, so this figure is not comparable with a state that has tested less.

Frequently Asked Questions

Is Illinois tap water safe to drink? ▼
94.3% of communities have no open violation on record. 22 have PFAS above the federal limit set in 2024, which is the main open concern.
Does Illinois have a lead problem? ▼
16 water systems report a 90th-percentile lead result at or above the 15 ppb action level. The action level is a treatment trigger, not a legal maximum, and 715 communities report no detection at all.
How complete is the data for Illinois? ▼
Lead results are reported for 100.0% of communities and PFAS for 41.0%. Where a figure is missing it is shown as not reported rather than assumed safe.
How does Illinois compare with other states? ▼
We do not rank states against each other. Lead reporting completeness ranges from under 20% to 100% depending on the state, so a national ranking would compare filing practice rather than water quality.