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Rock County, WI Water Quality

Water quality data for 13 public water systems serving Rock County, Wisconsin — based on EPA SDWIS enforcement records, lead testing results, and health-based violation history.

📅 2026 Report 🔄 Data updated 2026 Q2 📍 13 water systems · 24 cities
✅
Excellent — All Systems Performing Well

Water quality across the county is outstanding with minimal violations and very low lead levels.

A

Rock County Earns a A

Rock County: 24 communities across 13 water systems. 100.0% have no open violations.

  • Median lead where detected: 3.63 ppb
  • 20 communities with a lead detection, 4 reporting none detected
  • 0 communities with PFAS above the federal limit
  • 0 with significant inspection deficiencies
  • 100.0% of communities have no open violations
3.63 ppb
Median Lead Level
County-wide, 90th percentile
13
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
  • Clinton
    0.29 ppb
    No federal limits exceeded on record
    A
  • Orfordville
    0.68 ppb
    No federal limits exceeded on record
    B
  • Rock
    0.67 ppb
    No federal limits exceeded on record
    B
  • Magnolia
    1.60 ppb
    No federal limits exceeded on record
    B
  • Spring Valley
    0.68 ppb
    No federal limits exceeded on record
    B
⚠ Needs Attention
  • Evansville
    6.33 ppb
    6 health-based violations since 2015
    B
  • Union
    6.33 ppb
    6 health-based violations since 2015
    B
  • Center
    Not detected
    Copper above the 1,300 ppb action level
    B
  • Plymouth
    Not detected
    Copper above the 1,300 ppb action level
    B
  • Footville
    Not detected
    Copper above the 1,300 ppb action level
    B
County Lead Level — Median 3.63 ppb
Based on most recent 90th percentile lead tests across all reporting systems
0 ppb5 ppb10 ppb15 ppb
County median: 3.63 ppb — 24.2% of the federal action level
Systems by Lead Level
Under 5 ppb
13
5 – 10 ppb
2
10 – 15 ppb
5
No Data
4

All Cities in Rock County

Janesville 10.00 ppb A
Beloit 4.50 ppb A
Edgerton 2.76 ppb A
Evansville 6.33 ppb B
Milton 1.47 ppb A
Beloit 4.50 ppb A
Clinton 0.29 ppb A
Orfordville 0.68 ppb B
Rock 0.67 ppb B
Footville Not detected B
Harmony 10.00 ppb A
Turtle 4.50 ppb A
Union 6.33 ppb B
Janesville 10.00 ppb A
Fulton 10.10 ppb B
Lima Not detected B
Bradford 0.38 ppb B
La Prairie 10.00 ppb A
Magnolia 1.60 ppb B
Spring Valley 0.68 ppb B
Milton 1.47 ppb A
Clinton 0.29 ppb A
Center Not detected B
Plymouth Not detected B
Showing 24 cities
No active violations Active violations

About Rock County Drinking Water

Rock County is served by 13 water systems covering 24 communities. No community here has an open violation on record.

Of the communities reporting lead results, 20 recorded a detection, with a median of 3.63 ppb — 24% 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 no significant deficiencies.

Frequently Asked Questions

Is Rock County tap water safe to drink?▼
No community in Rock County has an open violation on record. No community has PFAS above the federal limit on record.
What is the lead level in Rock County?▼
Among communities with a detection the median is 3.63 ppb, 24% of the 15 ppb action level. 4 reported none detected and 0 reported no result.
How many water systems serve Rock County?▼
13 community water systems serve 24 communities here.
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