States › Illinois › Mercer County

Mercer County, IL Water Quality

Water quality data for 12 public water systems serving Mercer County, Illinois — based on EPA SDWIS enforcement records, lead testing results, and health-based violation history.

📅 2026 Report 🔄 Data updated 2026 Q2 📍 12 water systems · 13 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

Mercer County Earns a B

Mercer County: 13 communities across 12 water systems. 92.3% have no open violations.

  • Median lead where detected: 1.70 ppb
  • 9 communities with a lead detection, 4 reporting none detected
  • 0 communities with PFAS above the federal limit
  • 10 with significant inspection deficiencies
  • 92.3% of communities have no open violations
1.7 ppb
Median Lead Level
County-wide, 90th percentile
12
Water Systems
Active CWS & NTNCWS
92%
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
  • Aledo
    3.00 ppb
    No federal limits exceeded on record
    B
  • Viola
    Not detected
    No federal limits exceeded on record
    B
  • Seaton
    Not detected
    No federal limits exceeded on record
    B
  • New Boston
    Not detected
    2 significant inspection deficiencies
    B
  • Keithsburg
    Not detected
    1 significant inspection deficiency
    B
⚠ Needs Attention
  • Windsor
    6.20 ppb
    1 violation currently open
    F
  • Sherrard
    3.00 ppb
    Copper above the 1,300 ppb action level
    C
  • Joy
    1.70 ppb
    3 significant inspection deficiencies
    C
  • Millersburg
    1.70 ppb
    3 significant inspection deficiencies
    C
  • Matherville
    1.20 ppb
    5 significant inspection deficiencies
    B
County Lead Level — Median 1.7 ppb
Based on most recent 90th percentile lead tests across all reporting systems
0 ppb5 ppb10 ppb15 ppb
County median: 1.7 ppb — 11.3% of the federal action level
Systems by Lead Level
Under 5 ppb
8
5 – 10 ppb
1
No Data
4

All Cities in Mercer County

Aledo 3.00 ppb B
Viola Not detected B
Matherville 1.20 ppb B
Windsor 6.20 ppb F
Sherrard 3.00 ppb C
New Boston Not detected B
Keithsburg Not detected B
North Henderson 1.30 ppb B
Joy 1.70 ppb C
Swedona 0.70 ppb B
Seaton Not detected B
Preemption 1.00 ppb B
Millersburg 1.70 ppb C
Showing 13 cities
No active violations Active violations

About Mercer County Drinking Water

Mercer County is served by 12 water systems covering 13 communities. 92% have no open violations.

Of the communities reporting lead results, 9 recorded a detection, with a median of 1.70 ppb — 11% of the federal action level. 4 reported none detected, which means below the laboratory limit rather than an absence of lead.

No community here has PFAS above the federal limit on record. State inspectors recorded significant deficiencies at 10 of them.

Frequently Asked Questions

Is Mercer County tap water safe to drink?▼
92% of communities have no open violation. No community has PFAS above the federal limit on record.
What is the lead level in Mercer County?▼
Among communities with a detection the median is 1.70 ppb, 11% of the 15 ppb action level. 4 reported none detected and 0 reported no result.
How many water systems serve Mercer County?▼
12 community water systems serve 13 communities here.
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