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Not health advice. Contact your local water utility for concerns.
Data from EPA Water Quality Reports. For official information, contact your water utility or health department.
Water quality data for 4 cities serving 177,367 residents
Lake County in Illinois has an average water quality score of 92/100 (Grade A) based on analysis of 4 municipal water systems. The county's water systems serve approximately 177,367 residents.
Overall, Lake County demonstrates good water quality standards. 3 of 4 cities exceed the county average, with Gurnee leading with a score of 100/100.
4 cities ranked by water quality score
| Rank | City | Score | Grade | Population |
|---|---|---|---|---|
| 1 | Gurnee | 100 | A | 30,193 |
| 2 | Buffalo Grove Biggest deduction: 2 monitoring/reporting violations in the last 5 years (−2 pts) | 98 | A | 43,212 |
| 3 | Waukegan Biggest deduction: 4 monitoring/reporting violations in the last 5 years (−4 pts) | 93 | A | 87,149 |
| 4 | North Chicago Biggest deduction: 2 health-based violations (MCL/treatment-technique) in the last 5 years (−20 pts) | 78 | C | 16,813 |
Real EPA readings across county water systems (lead: latest 90th percentile; PFAS: UCMR5 2023–2026; others: 2012–2019 averages)
| Contaminant | Avg Level | Max Level | EPA Limit | % of Limit | Cities |
|---|---|---|---|---|---|
| TTHM (2012–2019 avg) | 27.63 ug/L | 33.327 ug/L | 80 ug/L | 34.5% | 4 |
| Fluoride (2012–2019 avg) | 0.856 mg/L | 0.9 mg/L | 4 mg/L | 21.4% | 2 |
| HAA5 (2012–2019 avg) | 11.989 ug/L | 14.87 ug/L | 60 ug/L | 20% | 4 |
| Lead (90th percentile) | 2.325 ppb | 9 ppb | 15 ppb | 15.5% | 4 |
| Arsenic (2012–2019 avg) | 0.419 ug/L | 0.538 ug/L | 10 ug/L | 4.2% | 2 |
| Nitrate (2012–2019 avg) | 0.389 mg/L | 0.398 mg/L | 10 mg/L | 3.9% | 2 |
| PFAS (PFOA/PFOS max, UCMR5) | 0 ppt | 0 ppt | 4 ppt | 0% | 4 |
| Radium (2012–2019 avg) | 0 pCi/L | 0 pCi/L | 5 pCi/L | 0% | 2 |
Recent violations across county water systems
Health-based: MCL exceeded — Maximum Contaminant Level Violation, Average - Di(2-ethylhexyl) phthalate
3/31/2024
Health-based: MCL exceeded — Maximum Contaminant Level Violation, Average - TTHM
3/31/2023
Monitoring & reporting — Follow-up Or Routine LCR Tap M/R - Lead and Copper Rule
6/30/2025
Other — Consumer Confidence Report Inadequate Reporting - Consumer Confidence Rule
6/30/2025
Monitoring & reporting — Monitoring and Reporting (DBP) - Total Haloacetic Acids (HAA5)
3/31/2025
Monitoring & reporting — Monitoring and Reporting (DBP) - Total Haloacetic Acids (HAA5)
9/30/2024
Showing 10 of 20 recent violations
Water quality in Lake County, Illinois reflects the region's unique combination of water sources, treatment infrastructure, and environmental factors. Our comprehensive analysis examines 4 municipal water systems serving a combined population of over 177,367 residents.
The county shows strong water quality performance, with scores ranging from 78/100 in North Chicago to 100/100 in Gurnee. This 22-point spread indicates significant variation in water quality across the county, suggesting different water sources or treatment approaches.
The most prevalent contaminants detected across Lake County water systems include TTHM (2012–2019 avg), Fluoride (2012–2019 avg), HAA5 (2012–2019 avg). Every county-wide average sits below 50% of its EPA Maximum Contaminant Level (MCL).
Lake County's water quality is generally good. Residents can feel confident in their tap water quality, though those with specific health concerns or sensitivity to certain contaminants may still benefit from filtration. Regular review of your city's annual Consumer Confidence Report is recommended.
Lake County has an average water quality score of 92/100 (Grade A) based on analysis of 4 municipal water systems serving 177,367 residents.
Gurnee has the highest water quality score in Lake County at 100/100. View the detailed report for Gurnee.
Most cities in Lake County have water that meets EPA standards. However, a water filter can provide additional protection and improve taste. The need depends on your specific city and any personal health considerations.
Click on any city in the rankings table above to view its detailed water quality report, including contaminant levels, EPA compliance history, and filter recommendations.