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Sonoma County, CA Water Quality

Water quality data for 31 public water systems serving Sonoma County, California — based on EPA SDWIS enforcement records, lead testing results, and health-based violation history.

📅 2026 Report 🔄 Data updated 2026 Q2 📍 31 water systems · 35 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

Sonoma County Earns a B

Sonoma County: 35 communities across 31 water systems. 91.4% have no open violations.

  • Median lead where detected: 2.95 ppb
  • 10 communities with a lead detection, 25 reporting none detected
  • 5 communities with PFAS above the federal limit
  • 0 with significant inspection deficiencies
  • 91.4% of communities have no open violations
2.95 ppb
Median Lead Level
County-wide, 90th percentile
31
Water Systems
Active CWS & NTNCWS
91%
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
  • Rohnert Park
    Not detected
    No federal limits exceeded on record
    A
  • Windsor
    Not detected
    No federal limits exceeded on record
    A
  • Sebastopol
    Not detected
    No federal limits exceeded on record
    A
  • Guerneville
    Not detected
    No federal limits exceeded on record
    B
  • Forestville
    Not detected
    No federal limits exceeded on record
    B
⚠ Needs Attention
  • Valley Ford
    9.00 ppb
    1 violation currently open
    D
  • Sea Ranch
    Not detected
    Copper above the 1,300 ppb action level
    D
  • Petaluma Center
    Not detected
    1 violation currently open
    C
  • Sonoma
    Not detected
    PFAS above the limit at 1 of 6 sampling points
    C
  • Boyes Hot Springs
    Not detected
    PFAS above the limit at 1 of 7 sampling points
    C
County Lead Level — Median 2.95 ppb
Based on most recent 90th percentile lead tests across all reporting systems
0 ppb5 ppb10 ppb15 ppb
County median: 2.95 ppb — 19.7% of the federal action level
Systems by Lead Level
Under 5 ppb
7
5 – 10 ppb
3
No Data
25

All Cities in Sonoma County

Santa Rosa 1.32 ppb A
Petaluma Not detected A
Rohnert Park Not detected A
Windsor Not detected A
Healdsburg Not detected A
Sonoma Not detected C
Cloverdale Not detected A
Larkfield-Wikiup 6.00 ppb A
Sebastopol Not detected A
Cotati Not detected A
Boyes Hot Springs Not detected C
Fetters Hot Springs-Agua Caliente Not detected C
Guerneville Not detected B
El Verano Not detected C
Sonoma State University Not detected A
Penngrove Not detected B
Forestville Not detected B
Eldridge Not detected C
Sea Ranch Not detected D
Monte Rio Not detected B
Bodega Bay 1.90 ppb B
Geyserville Not detected A
Petaluma Center Not detected C
Kenwood Not detected B
Occidental 3.80 ppb B
Fulton 6.00 ppb A
Cazadero Not detected C
Graton 3.20 ppb B
Timber Cove Not detected B
Sereno del Mar Not detected B
Jenner 2.70 ppb C
Salmon Creek Not detected B
Valley Ford 9.00 ppb D
Carmet 2.20 ppb B
Bodega 1.80 ppb C
Showing 35 cities
No active violations Active violations

About Sonoma County Drinking Water

Sonoma County is served by 31 water systems covering 35 communities. 91% have no open violations.

Of the communities reporting lead results, 10 recorded a detection, with a median of 2.95 ppb — 20% of the federal action level. 25 reported none detected, which means below the laboratory limit rather than an absence of lead.

5 of 35 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 Sonoma County tap water safe to drink?▼
91% of communities have no open violation. 5 of 35 have PFAS above the federal limit, which is the main open concern.
What is the lead level in Sonoma County?▼
Among communities with a detection the median is 2.95 ppb, 20% of the 15 ppb action level. 25 reported none detected and 0 reported no result.
How many water systems serve Sonoma County?▼
31 community water systems serve 35 communities here.
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