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Napa County, CA Water Quality

Water quality data for 7 public water systems serving Napa County, California — based on EPA SDWIS enforcement records, lead testing results, and health-based violation history.

📅 2026 Report 🔄 Data updated 2026 Q2 📍 7 water systems · 11 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

Napa County Earns a B

Napa County: 11 communities across 7 water systems. 90.9% have no open violations.

  • Median lead where detected: 3.30 ppb
  • 1 communities with a lead detection, 10 reporting none detected
  • 0 communities with PFAS above the federal limit
  • 0 with significant inspection deficiencies
  • 90.9% of communities have no open violations
3.3 ppb
Median Lead Level
County-wide, 90th percentile
7
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
  • Yountville
    Not detected
    Copper above the 1,300 ppb action level
    B
  • Napa
    Not detected
    5 health-based violations since 2015
    B
  • American Canyon
    Not detected
    9 health-based violations since 2015
    B
  • St. Helena
    Not detected
    11 health-based violations since 2015
    B
  • Calistoga
    Not detected
    12 health-based violations since 2015
    B
⚠ Needs Attention
  • Moskowite Corner
    3.30 ppb
    1 violation currently open
    C
  • Napa
    Not detected
    5 health-based violations since 2015
    B
  • American Canyon
    Not detected
    9 health-based violations since 2015
    B
  • St. Helena
    Not detected
    11 health-based violations since 2015
    B
  • Calistoga
    Not detected
    12 health-based violations since 2015
    B
County Lead Level — Median 3.3 ppb
Based on most recent 90th percentile lead tests across all reporting systems
0 ppb5 ppb10 ppb15 ppb
County median: 3.3 ppb — 22% of the federal action level
Systems by Lead Level
Under 5 ppb
1
No Data
10

All Cities in Napa County

Napa Not detected B
American Canyon Not detected B
St. Helena Not detected B
Calistoga Not detected B
Yountville Not detected B
Angwin Not detected B
Silverado Resort Not detected B
Deer Park Not detected B
Moskowite Corner 3.30 ppb C
Rutherford Not detected B
Oakville Not detected B
Showing 11 cities
No active violations Active violations

About Napa County Drinking Water

Napa County is served by 7 water systems covering 11 communities. 91% have no open violations.

Of the communities reporting lead results, 1 recorded a detection, with a median of 3.30 ppb — 22% of the federal action level. 10 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 Napa County tap water safe to drink?▼
91% of communities have no open violation. No community has PFAS above the federal limit on record.
What is the lead level in Napa County?▼
Among communities with a detection the median is 3.30 ppb, 22% of the 15 ppb action level. 10 reported none detected and 0 reported no result.
How many water systems serve Napa County?▼
7 community water systems serve 11 communities here.
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