States › Illinois › McHenry County

McHenry County, IL Water Quality

Water quality data for 20 public water systems serving McHenry County, Illinois — based on EPA SDWIS enforcement records, lead testing results, and health-based violation history.

📅 2026 Report 🔄 Data updated 2026 Q2 📍 20 water systems · 25 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

McHenry County Earns a B

McHenry County: 25 communities across 20 water systems. 100.0% have no open violations.

  • Median lead where detected: 1.80 ppb
  • 15 communities with a lead detection, 10 reporting none detected
  • 3 communities with PFAS above the federal limit
  • 12 with significant inspection deficiencies
  • 100.0% of communities have no open violations
1.8 ppb
Median Lead Level
County-wide, 90th percentile
20
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
  • Crystal Lake
    4.30 ppb
    No federal limits exceeded on record
    A
  • McHenry
    4.10 ppb
    No federal limits exceeded on record
    A
  • Cary
    4.10 ppb
    No federal limits exceeded on record
    A
  • Trout Valley
    4.10 ppb
    No federal limits exceeded on record
    A
  • Oakwood Hills
    Not detected
    1 significant inspection deficiency
    B
⚠ Needs Attention
  • Johnsburg
    Not detected
    PFAS above the limit at 1 of 5 sampling points
    C
  • Pistakee Highlands
    Not detected
    PFAS above the limit at 1 of 5 sampling points
    C
  • Wonder Lake
    1.80 ppb
    Copper above the 1,300 ppb action level
    C
  • Spring Grove
    Not detected
    PFAS above the limit at 1 of 5 sampling points
    C
  • Bull Valley
    1.80 ppb
    Copper above the 1,300 ppb action level
    C
County Lead Level — Median 1.8 ppb
Based on most recent 90th percentile lead tests across all reporting systems
0 ppb5 ppb10 ppb15 ppb
County median: 1.8 ppb — 12% of the federal action level
Systems by Lead Level
Under 5 ppb
13
5 – 10 ppb
2
No Data
10

All Cities in McHenry County

Crystal Lake 4.30 ppb A
Lake in the Hills Not detected A
Algonquin 0.40 ppb B
Woodstock 7.00 ppb C
Huntley Not detected B
McHenry 4.10 ppb A
Cary 4.10 ppb A
Harvard 1.40 ppb A
Island Lake Not detected B
Marengo Not detected B
Fox River Grove Not detected B
Johnsburg Not detected C
Pistakee Highlands Not detected C
Wonder Lake 1.80 ppb C
Lakewood 1.50 ppb B
Richmond 8.70 ppb B
Hebron 4.50 ppb B
Spring Grove Not detected C
Prairie Grove 1.00 ppb B
Union 1.80 ppb B
Trout Valley 4.10 ppb A
Bull Valley 1.80 ppb C
Greenwood 1.80 ppb C
Ringwood Not detected B
Oakwood Hills Not detected B
Showing 25 cities
No active violations Active violations

About McHenry County Drinking Water

McHenry County is served by 20 water systems covering 25 communities. No community here has an open violation on record.

Of the communities reporting lead results, 15 recorded a detection, with a median of 1.80 ppb — 12% of the federal action level. 10 reported none detected, which means below the laboratory limit rather than an absence of lead.

3 of 25 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 12 of them.

Frequently Asked Questions

Is McHenry County tap water safe to drink?▼
No community in McHenry County has an open violation on record. 3 of 25 have PFAS above the federal limit, which is the main open concern.
What is the lead level in McHenry County?▼
Among communities with a detection the median is 1.80 ppb, 12% of the 15 ppb action level. 10 reported none detected and 0 reported no result.
How many water systems serve McHenry County?▼
20 community water systems serve 25 communities here.
← Back to Illinois water quality overview