Is Angwin, CA Tap Water Safe to Drink?
Graded B, with 7 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
76.9/100
waterverge.com Angwin, CA — Water Quality Report
Angwin's drinking water received a grade of B (76.9 out of 100), indicating good water quality. The city's 5 water systems serve approximately 3,390 residents using groundwater.
Lead levels were measured at 0.0 ppb (90th percentile), well within EPA limits. This system has not yet been tested for PFAS under the EPA UCMR 5 program.
The system has 73 violations on record, including 37 health-based violations. 7 remain unresolved.
What to know about Angwin's water
Angwin ranks #426 out of 694 cities in California for water quality, placing it below average in the state.
Angwin relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff.
Water quality score
See methodology →Is Angwin, CA water safe to drink?
Angwin's drinking water has significant quality concerns based on EPA testing data. With a grade of B (76.9/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 5 water systems serve approximately 3,390 residents using groundwater (wells).
Recent water quality updates for Angwin
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Angwin's water quality assessment. Grade: B (76.9/100).
1 health-based. Contaminants: LEAD AND COPPER RULE REVISIONS.
Federal disaster declaration (FEMA DR-3592). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-4683). Flood event — may have impacted local water infrastructure.
1 health-based. Contaminants: TTHM.
Contaminants: Revised Total Coliform Rule.
Key contaminant findings
Based on the most recent EPA sampling data for Angwin's water supply.
Well within EPA limits.
Violation history
Angwin's water system has 73 total violations on record, including 37 health-based violations. 7 remain unresolved. 5 violations were issued in the last 5 years.
Flood & environmental risk
Napa County has experienced 10 federally declared disasters since 1964. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies. Local water sources include Pope C A Walter Springs, Napa R Nr St Helena.
Where does Angwin's water come from?
Angwin's drinking water comes from groundwater (wells), supplied by 5 water systems serving approximately 3,390 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Pope C A Walter Springs (river), Napa R Nr St Helena (river).
What Angwin residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Angwin's water.
Your water utility is required to publish an annual Consumer Confidence Report (CCR) with detailed testing results. Ask for the latest copy or check your utility's website.
Angwin's area has a history of flooding. After severe weather, watch for boil water advisories from your local utility.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Violation summary
Violations & advisories
Flood & disaster history
Napa County has experienced 10 federally declared disasters since 1964. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 0.0 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how Angwin compares by contaminant
Explore where Angwin ranks among all California cities for specific contaminants.
Water source & infrastructure
Where Angwin's water comes from
Angwin's drinking water is drawn from underground aquifers through wells.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals.
Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds.
The system is operated by private ownership and serves approximately 3,390 people through 5 water systems.
Water bodies near Angwin
Angwin is located near 2 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Angwin
| System Name | PWSID | Population | Source |
|---|---|---|---|
| PACIFIC UNION COLLEGE | CA2810012 | 1,958 | GW |
| HOWELL MOUNTAIN MUTUAL WATER COMPANY | CA2810001 | 1,240 | SW |
| LINDA VISTA MUTUAL WATER CO | CA2800528 | 90 | GW |
| LA TIERRA HEIGHTS MUTUAL | CA2800525 | 67 | GW |
| LINDA FALLS TERRACE MUTUAL | CA2800527 | 35 | GW |
How Angwin compares
Full California rankings →Angwin's score of 76.9/100 is above the average of 57/100 among major California cities. It outscores 7 of 10 nearby cities.
Nearby cities
View California rankings →About Angwin, CA
Learn more about your water
Guides and resources related to Angwin's water quality findings.
Explore water quality across Napa
Frequently asked questions
Is Angwin, CA tap water safe to drink?
Angwin's water quality earned a grade of B (76.9/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #426 out of 694 cities tested in California.
What contaminants are in Angwin's water?
Lead was measured at 0.0 ppb (90th percentile). 73 violations are on record.
How is Angwin's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Angwin?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Angwin's water come from?
Angwin's water is sourced from Groundwater. The city has 5 water systems serving approximately 3,390 residents.
What health violations has Angwin's water system had?
Angwin has 37 health-based violations on record. The most recent violation was recorded in October 2024. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 7 violations remain unresolved.
Is Angwin's groundwater at risk of contamination?
Angwin uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 73 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Angwin's water compare to other cities?
Angwin ranks #426 out of 694 cities in California (better than 39% of state cities) and #9156 out of 15744 cities nationally (42th percentile). The grade of B reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.