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Stanislaus County, CA Water Quality

Water quality data for 24 public water systems serving Stanislaus County, California — based on EPA SDWIS enforcement records, lead testing results, and health-based violation history.

📅 2026 Report 🔄 Data updated 2026 Q2 📍 24 water systems · 31 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

Stanislaus County Earns a B

Stanislaus County: 31 communities across 24 water systems. 90.3% have no open violations.

  • Median lead where detected: 5.00 ppb
  • 3 communities with a lead detection, 26 reporting none detected
  • 8 communities with PFAS above the federal limit
  • 0 with significant inspection deficiencies
  • 90.3% of communities have no open violations
5 ppb
Median Lead Level
County-wide, 90th percentile
24
Water Systems
Active CWS & NTNCWS
90%
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
  • Patterson
    Not detected
    No federal limits exceeded on record
    A
  • Waterford
    Not reported
    No federal limits exceeded on record
    B
  • Denair
    Not detected
    No federal limits exceeded on record
    A
  • Empire
    Not reported
    No federal limits exceeded on record
    B
  • Del Rio
    Not detected
    No federal limits exceeded on record
    B
⚠ Needs Attention
  • Ceres
    Not detected
    PFAS above the limit at 1 of 8 sampling points
    F
  • Hughson
    Not detected
    1 violation currently open
    D
  • Knights Ferry
    9.60 ppb
    Copper above the 1,300 ppb action level
    C
  • Crows Landing
    Not detected
    1 violation currently open
    C
  • Modesto
    Not detected
    PFAS above the limit at 6 of 42 sampling points
    C
County Lead Level — Median 5 ppb
Based on most recent 90th percentile lead tests across all reporting systems
0 ppb5 ppb10 ppb15 ppb
County median: 5 ppb — 33.3% of the federal action level
Systems by Lead Level
Under 5 ppb
1
5 – 10 ppb
2
No Data
28

All Cities in Stanislaus County

Modesto Not detected C
Turlock Not detected A
Ceres Not detected F
Patterson Not detected A
Oakdale Not detected A
Riverbank Not detected A
Newman Not detected A
Hughson Not detected D
Salida Not detected A
Bret Harte Not detected C
Keyes Not detected B
Waterford Not reported B
Denair Not detected A
Bystrom Not detected C
West Modesto Not detected C
Empire Not reported B
Diablo Grande Not detected B
Del Rio Not detected B
Parklawn Not detected C
Rouse Not detected C
Grayson Not detected B
Riverdale Park 5.00 ppb B
Airport Not detected C
East Oakdale Not detected B
Hickman 2.25 ppb B
Westley Not detected B
Crows Landing Not detected C
Orange Blossom Not detected B
La Grange Not detected B
Monterey Park Tract Not detected B
Knights Ferry 9.60 ppb C
Showing 31 cities
No active violations Active violations

About Stanislaus County Drinking Water

Stanislaus County is served by 24 water systems covering 31 communities. 90% have no open violations.

Of the communities reporting lead results, 3 recorded a detection, with a median of 5.00 ppb — 33% of the federal action level. 26 reported none detected, which means below the laboratory limit rather than an absence of lead.

8 of 31 communities have PFAS above the limits EPA set in 2024, measured as a running annual average at each sampling point. State inspectors recorded no significant deficiencies.

Frequently Asked Questions

Is Stanislaus County tap water safe to drink?▼
90% of communities have no open violation. 8 of 31 have PFAS above the federal limit, which is the main open concern.
What is the lead level in Stanislaus County?▼
Among communities with a detection the median is 5.00 ppb, 33% of the 15 ppb action level. 26 reported none detected and 2 reported no result.
How many water systems serve Stanislaus County?▼
24 community water systems serve 31 communities here.
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