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St. Clair County, IL Water Quality

Water quality data for 17 public water systems serving St. Clair County, Illinois — based on EPA SDWIS enforcement records, lead testing results, and health-based violation history.

📅 2026 Report 🔄 Data updated 2026 Q2 📍 17 water systems · 24 cities
✅
Generally Safe — Most Systems Performing Well

The majority of water systems have no active violations and lead levels well below the federal action level.

B

St. Clair County Earns a B

St. Clair County: 24 communities across 17 water systems. 100.0% have no open violations.

  • Median lead where detected: 3.00 ppb
  • 13 communities with a lead detection, 11 reporting none detected
  • 1 communities with PFAS above the federal limit
  • 21 with significant inspection deficiencies
  • 100.0% of communities have no open violations
3 ppb
Median Lead Level
County-wide, 90th percentile
17
Water Systems
Active CWS & NTNCWS
100%
Violation-Free
No active violations on record
How we grade counties: MyWaterIQ uses EPA SDWIS enforcement data — actual MCL violations and lead test results — not the aspirational MCLG targets used by some sites. A grade reflects real compliance history, not theoretical risk. Learn more →

Cities by Water Quality

⭐ Best Performing
  • Summerfield
    3.43 ppb
    No federal limits exceeded on record
    B
  • O'Fallon
    Not detected
    1 significant inspection deficiency
    A
  • Fairview Heights
    Not detected
    1 significant inspection deficiency
    A
  • Smithton
    Not detected
    2 significant inspection deficiencies
    B
  • St. Libory
    Not detected
    1 significant inspection deficiency
    B
⚠ Needs Attention
  • Mascoutah
    6.00 ppb
    3 significant inspection deficiencies
    C
  • Lenzburg
    Not detected
    Copper above the 1,300 ppb action level
    C
  • Lebanon
    12.20 ppb
    2 significant inspection deficiencies
    C
  • Freeburg
    5.60 ppb
    2 significant inspection deficiencies
    C
  • Dupo
    Not detected
    PFAS above the limit at 1 of 1 sampling points
    B
County Lead Level — Median 3 ppb
Based on most recent 90th percentile lead tests across all reporting systems
0 ppb5 ppb10 ppb15 ppb
County median: 3 ppb — 20% of the federal action level
Systems by Lead Level
Under 5 ppb
9
5 – 10 ppb
3
10 – 15 ppb
1
No Data
11

All Cities in St. Clair County

Belleville 3.00 ppb B
O'Fallon Not detected A
East St. Louis 3.00 ppb B
Swansea 3.00 ppb B
Shiloh 3.00 ppb B
Fairview Heights Not detected A
Mascoutah 6.00 ppb C
Lebanon 12.20 ppb C
Freeburg 5.60 ppb C
Dupo Not detected B
Smithton Not detected B
Scott AFB 6.00 ppb B
Millstadt Not detected B
Caseyville Not detected B
Washington Park 3.00 ppb B
Fairmont City 3.00 ppb B
New Athens Not detected B
Marissa 2.30 ppb B
St. Libory Not detected B
Brooklyn 3.00 ppb B
Lenzburg Not detected C
Summerfield 3.43 ppb B
Fayetteville Not detected B
Sauget Not detected A
Showing 24 cities
No active violations Active violations

About St. Clair County Drinking Water

St. Clair County is served by 17 water systems covering 24 communities. No community here has an open violation on record.

Of the communities reporting lead results, 13 recorded a detection, with a median of 3.00 ppb — 20% of the federal action level. 11 reported none detected, which means below the laboratory limit rather than an absence of lead.

1 of 24 communities have PFAS above the limits EPA set in 2024, measured as a running annual average at each sampling point. State inspectors recorded significant deficiencies at 21 of them.

Frequently Asked Questions

Is St. Clair County tap water safe to drink?▼
No community in St. Clair County has an open violation on record. 1 of 24 have PFAS above the federal limit, which is the main open concern.
What is the lead level in St. Clair County?▼
Among communities with a detection the median is 3.00 ppb, 20% of the 15 ppb action level. 11 reported none detected and 0 reported no result.
How many water systems serve St. Clair County?▼
17 community water systems serve 24 communities here.
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