Illinois Water Quality Report 2026
Illinois tap water is use filtration based on our analysis of 11 water systems serving 3,937,111 residents. The average PurityMap score is 76.7/100 (Grade: C), which is 1.2 points below the national average.
- PFAS detected in 1 of 11 cities (9%). Forever chemicals require reverse osmosis filtration.
- 8 cities have lead at or above 5 ppb. Homes built before 1986 are at highest risk.
- 9 cities (82%) have hard or very hard water (7+ GPG) which causes scale buildup and appliance damage.
- 1 cities exceed the EPA secondary TDS guideline of 500 ppm, which affects taste and may indicate elevated minerals.
- 11 cities use chloramine or have elevated chlorine residuals. Standard Brita pitchers do not remove chloramine.
We recommend an under-sink reverse osmosis system for drinking water in PFAS-affected areas of Illinois. RO removes 99%+ of PFAS, lead, and other contaminants. For hard water cities, add a whole-house softener.
Hard
Illinois is 1.2 points below the US average of 77.9/100. Hardness is 2.8 GPG above the US average of 6.3 GPG.
Cities ranked by lowest score. Click any city for the full report and filter recommendations.
| Rank | City | Score | Hardness | Lead | Key Issues |
|---|---|---|---|---|---|
| 1 | Rockford | 58/100 | 10.5 GPG | 7.2 ppb | PFAS (2.4 ppt), Very Hard (10.5 GPG), Lead (7.2 ppb) |
| 2 | Champaign | 73/100 | 14.5 GPG | 3.0 ppb | Very Hard (14.5 GPG), TDS (580 ppm) |
| 3 | Elgin | 75/100 | 11.2 GPG | 5.5 ppb | Very Hard (11.2 GPG), Lead (5.5 ppb) |
| 4 | Chicago | 79/100 | 8.4 GPG | 8.0 ppb | Hard (8.4 GPG), Lead (8.0 ppb) |
| 5 | Aurora | 79/100 | 9.6 GPG | 6.5 ppb | Hard (9.6 GPG), Lead (6.5 ppb) |
| 6 | Naperville | 79/100 | 8.8 GPG | 5.8 ppb | Hard (8.8 GPG), Lead (5.8 ppb) |
| 7 | Joliet | 79/100 | 8.5 GPG | 6.0 ppb | Hard (8.5 GPG), Lead (6.0 ppb) |
| 8 | Peoria | 79/100 | 8.2 GPG | 5.5 ppb | Hard (8.2 GPG), Lead (5.5 ppb) |
| 9 | Waukegan | 79/100 | 8.4 GPG | 6.0 ppb | Hard (8.4 GPG), Lead (6.0 ppb) |
| 10 | Springfield | 82/100 | 5.5 GPG | 3.5 ppb | Hardness 5.5 GPG, Lead 3.5 ppb |
How Illinois's 11 cities score on the PurityMap 0–100 scale:
Water quality for the most populated cities. Click any city for details.
| City | Population | Score | Hardness | Key Issues |
|---|---|---|---|---|
| Chicago | 2.7M | 79/100 | 8.4 GPG | Hard, Lead |
| Aurora | 198K | 79/100 | 9.6 GPG | Hard, Lead |
| Naperville | 150K | 79/100 | 8.8 GPG | Hard, Lead |
| Rockford | 149K | 58/100 | 10.5 GPG | PFAS, Very Hard, Lead |
| Joliet | 147K | 79/100 | 8.5 GPG | Hard, Lead |
| Springfield | 116K | 82/100 | 5.5 GPG | — |
| Elgin | 115K | 75/100 | 11.2 GPG | Very Hard, Lead |
| Peoria | 113K | 79/100 | 8.2 GPG | Hard, Lead |
| Waukegan | 89K | 79/100 | 8.4 GPG | Hard, Lead |
| Champaign | 88K | 73/100 | 14.5 GPG | Very Hard |
| Decatur | 73K | 82/100 | 6.8 GPG | — |
9 of 11 cities (82%) in Illinois have hard or very hard water (7+ GPG). Champaign has the hardest at 14.5 GPG. Cities: Champaign, Elgin, Rockford, Aurora, Naperville, Joliet, Chicago, Waukegan. A water softener is recommended.
PFAS have been detected in 1 of 11 cities (9%) in Illinois. Highest: Rockford at 2.4 ppt. Affected: Rockford. A reverse osmosis filter is recommended.
8 cities in Illinois have lead at or above 5 ppb. Highest: Chicago at 8.0 ppb. No safe level of lead exists. Cities: Chicago, Rockford, Aurora, Joliet, Waukegan, Naperville, Peoria, Elgin.
1 cities in Illinois have TDS above 500 ppm. Cities: Champaign. RO effectively reduces TDS.
Where Illinois gets its drinking water, based on 11 water systems.
| Source Type | Cities | % of Total |
|---|---|---|
| Surface Water | 7 | 64% |
| Mixed (Ground + Surface) | 3 | 27% |
| Groundwater | 1 | 9% |
Illinois has both PFAS (1 cities) and hard water (9 cities). RO for drinking water + softener for whole house.
| # | City | Pop. | Score | Hardness | Lead | PFAS | TDS |
|---|---|---|---|---|---|---|---|
| 1 | Rockford | 149K | 58/100 | 10.5 GPG (Hard) | 7.2 ppb | ⚠️ Yes (2.4 ppt) | 350 ppm |
| 2 | Champaign | 88K | 73/100 | 14.5 GPG (Very Hard) | 3.0 ppb | ✅ No | 580 ppm |
| 3 | Elgin | 115K | 75/100 | 11.2 GPG (Very Hard) | 5.5 ppb | ✅ No | 375 ppm |
| 4 | Aurora | 198K | 79/100 | 9.6 GPG (Hard) | 6.5 ppb | ✅ No | 280 ppm |
| 5 | Naperville | 150K | 79/100 | 8.8 GPG (Hard) | 5.8 ppb | ✅ No | 220 ppm |
| 6 | Joliet | 147K | 79/100 | 8.5 GPG (Hard) | 6.0 ppb | ✅ No | 215 ppm |
| 7 | Peoria | 113K | 79/100 | 8.2 GPG (Hard) | 5.5 ppb | ✅ No | 275 ppm |
| 8 | Chicago | 2.7M | 79/100 | 8.4 GPG (Hard) | 8.0 ppb | ✅ No | 210 ppm |
| 9 | Waukegan | 89K | 79/100 | 8.4 GPG (Hard) | 6.0 ppb | ✅ No | 210 ppm |
| 10 | Springfield | 116K | 82/100 | 5.5 GPG (Moderate) | 3.5 ppb | ✅ No | 190 ppm |
| 11 | Decatur | 73K | 82/100 | 6.8 GPG (Moderate) | 4.0 ppb | ✅ No | 235 ppm |
Illinois has 11 utilities. Major: Chicago Department of Water Management, City of Aurora Water Production, City of Rockford Water Division, City of Naperville Water Utilities, City of Joliet Water.
Sources: Lake Michigan, Fox River and Lake Michigan blend, Rock River and groundwater, DuPage Water Commission Lake Michigan, Lake Springfield.
- EPA Safe Drinking Water Information System
- EWG Tap Water Database
- State utility Consumer Confidence Reports
- USGS regional water monitoring data
PurityMap compiles publicly available data and does not perform independent testing.
11 city water quality reports available for Illinois.
Champaign Water Quality Report
Chicago Water Quality Report
Decatur Water Quality Report
Elgin Water Quality Report
Joliet Water Quality Report
Naperville Water Quality Report
Peoria Water Quality Report
Rockford Water Quality Report
Springfield Water Quality Report
Waukegan Water Quality Report
Compare water quality reports across all 50 US states