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Yolo County, CA Water Quality

Water quality data for 12 public water systems serving Yolo County, California — based on EPA SDWIS enforcement records, lead testing results, and health-based violation history.

📅 2026 Report 🔄 Data updated 2026 Q2 📍 12 water systems · 14 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

Yolo County Earns a B

Yolo County: 14 communities across 12 water systems. 71.4% have no open violations.

  • Median lead where detected: 5.00 ppb
  • 2 communities with a lead detection, 12 reporting none detected
  • 0 communities with PFAS above the federal limit
  • 2 with significant inspection deficiencies
  • 71.4% of communities have no open violations
5 ppb
Median Lead Level
County-wide, 90th percentile
12
Water Systems
Active CWS & NTNCWS
71%
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
  • Davis
    Not detected
    No federal limits exceeded on record
    A
  • Woodland
    Not detected
    No federal limits exceeded on record
    A
  • University of California-Davis
    Not detected
    No federal limits exceeded on record
    A
  • Esparto
    Not detected
    No federal limits exceeded on record
    B
  • Winters
    Not detected
    No federal limits exceeded on record
    A
⚠ Needs Attention
  • Knights Landing
    Not detected
    1 violation currently open
    D
  • West Sacramento
    Not detected
    1 violation currently open
    C
  • Madison
    Not detected
    1 violation currently open
    C
  • Yolo
    Not detected
    1 violation currently open
    C
  • Guinda
    5.00 ppb
    Copper above the 1,300 ppb action level
    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
5 – 10 ppb
2
No Data
12

All Cities in Yolo County

Davis Not detected A
Woodland Not detected A
West Sacramento Not detected C
University of California-Davis Not detected A
Esparto Not detected B
Winters Not detected A
Knights Landing Not detected D
El Macero Not detected A
Monument Hills Not detected B
Madison Not detected C
Yolo Not detected C
Dunnigan Not detected B
Guinda 5.00 ppb C
Tancred 5.00 ppb C
Showing 14 cities
No active violations Active violations

About Yolo County Drinking Water

Yolo County is served by 12 water systems covering 14 communities. 71% have no open violations.

Of the communities reporting lead results, 2 recorded a detection, with a median of 5.00 ppb — 33% of the federal action level. 12 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 significant deficiencies at 2 of them.

Frequently Asked Questions

Is Yolo County tap water safe to drink?▼
71% of communities have no open violation. No community has PFAS above the federal limit on record.
What is the lead level in Yolo County?▼
Among communities with a detection the median is 5.00 ppb, 33% of the 15 ppb action level. 12 reported none detected and 0 reported no result.
How many water systems serve Yolo County?▼
12 community water systems serve 14 communities here.
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