Is Clearlake Oak, CA Tap Water Safe to Drink?
Graded B+ — but Copper was detected above EPA limits. Here's what's in the water and how to remove it. What to do next ↓
81.2/100
waterverge.com Clearlake Oak, CA — Water Quality Report
Clearlake Oak's drinking water received a grade of B+ (81.2 out of 100), indicating good water quality. The city's 1 water system serves approximately 2,359 residents using surface water.
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 10 violations on record, including 4 health-based violations. 3 remain unresolved.
What to know about Clearlake Oak's water
Clearlake Oak ranks #353 out of 694 cities in California for water quality, placing it below average in the state.
The city draws from surface water sources, which are more susceptible to seasonal runoff and agricultural contamination, requiring extensive multi-barrier treatment including coagulation, filtration, and disinfection.
As a small community water system, Clearlake Oak may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Clearlake Oak, CA water safe to drink?
Clearlake Oak's drinking water has significant quality concerns based on EPA testing data. With a grade of B+ (81.2/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 2,359 residents using surface water (rivers, lakes, or reservoirs).
Recent water quality updates for Clearlake Oak
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Clearlake Oak's water quality assessment. Grade: B+ (81.2/100).
1 health-based. Contaminants: TTHM.
1 health-based. Contaminants: TTHM.
Contaminants: Lead and Copper Rule.
Key contaminant findings
Based on the most recent EPA sampling data for Clearlake Oak's water supply.
Well within EPA limits.
Exceeds EPA action level. Copper can leach from household plumbing — flush taps for 30 seconds before drinking.
Violation history
Clearlake Oak's water system has 10 total violations on record, including 4 health-based violations. 3 remain unresolved. 2 violations were issued in the last 5 years.
Where does Clearlake Oak's water come from?
Clearlake Oak's drinking water comes from surface water (rivers, lakes, or reservoirs), supplied by 1 water system serving approximately 2,359 people. Surface water sources are more susceptible to contamination from runoff, industrial discharge, and algal blooms, requiring extensive treatment.
What Clearlake Oak residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Clearlake Oak'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.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Violation summary
Violations & advisories
Recommended water filters
Based on contaminants detected in Clearlake Oak's water supply, we recommend the following filter types.
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 |
| Copper (90th percentile) CopperInorganic A metal that enters drinking water mainly through corrosion of copper plumbing. Small amounts are essential for health, but excess levels are harmful. Health EffectsGastrointestinal distress (nausea, vomiting, diarrhea) at short-term high levels; liver and kidney damage from long-term exposure. EPA Limit1.3 mg/L action level Common SourcesCorrosion of copper household plumbing, erosion of natural deposits. | 2.80 | 1.3 | mg/L | Inorganic | Over Limit |
Lead level trend (90th percentile)
Copper level (90th percentile)
Latest reading: 2.800 mg/L (1995)
EPA action level: 1.3 mg/L
See how Clearlake Oak compares by contaminant
Explore where Clearlake Oak ranks among all California cities for specific contaminants.
Water source & infrastructure
Where Clearlake Oak's water comes from
Clearlake Oak's drinking water comes primarily from surface water sources such as rivers, lakes, or reservoirs.
Surface water systems require multi-stage treatment including coagulation, sedimentation, filtration, and disinfection to meet EPA Safe Drinking Water Act standards.
These sources can be impacted by seasonal changes, stormwater runoff, upstream agriculture, and industrial discharge.
The system is operated by local government ownership and serves approximately 2,359 people through 1 water system.
Water systems serving Clearlake Oak
| System Name | PWSID | Population | Source |
|---|---|---|---|
| CLEARLAKE OAKS COUNTY WATER DISTRICT | CA1710001 | 2,359 | SW |
How Clearlake Oak compares
Full California rankings →Clearlake Oak's score of 81.2/100 is above the average of 57/100 among major California cities. It outscores 8 of 10 nearby cities.
Nearby cities
View California rankings →Learn more about your water
Guides and resources related to Clearlake Oak's water quality findings.
Explore water quality across Lake
Frequently asked questions
Is Clearlake Oak, CA tap water safe to drink?
Clearlake Oak's water quality earned a grade of B+ (81.2/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #353 out of 694 cities tested in California.
What contaminants are in Clearlake Oak's water?
Lead was measured at 0.0 ppb (90th percentile). 10 violations are on record.
How is Clearlake Oak'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 Clearlake Oak?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Clearlake Oak's water come from?
Clearlake Oak's water is sourced from Surface water. The city has 1 water system serving approximately 2,359 residents.
What health violations has Clearlake Oak's water system had?
Clearlake Oak has 4 health-based violations on record. The most recent violation was recorded in October 2023. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 3 violations remain unresolved.
How does Clearlake Oak's water compare to other cities?
Clearlake Oak ranks #353 out of 694 cities in California (better than 49% of state cities) and #7561 out of 15744 cities nationally (52th percentile). The grade of B+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Clearlake Oak's small water system affect quality?
Clearlake Oak's system serves approximately 2,359 residents. Small community water systems (under 3,300 people) may have fewer financial resources for infrastructure upgrades and advanced treatment technologies. However, they are held to the same EPA drinking water standards as larger systems. This system has 10 violations on record.