B67/100
Clearlake Oak Tap Water Quality: Is It Safe to Drink? (2026 Report)
Serving 2,359 residents · California
What's In Clearlake Oak's Tap Water?
9
Contaminants Tested
1
Exceed EPA Limits
0
Above EPA Goals
1 contaminant above EPA health goals
| Contaminant | Detected | Limit (MCL) | Status |
|---|---|---|---|
Copper (90th percentile) | 2.80 mg/L | 1.30 mg/L | Over Limit |
EPA Violation History
1
Violation (last 5yr)
0
Unresolved
1
Health-Related
TIER 2Resolved
Exceeded the Maximum Contaminant Level (running average)
When: October 1, 2023 – December 31, 2023Rule: Stage 2 DBPREnforcement: Formal — state order issued
Understanding violation severity
Tier 1Urgent health risk. Utility must notify all customers within 24 hours.Tier 2Important health or treatment issue. Customers notified within 30 days.Tier 3Administrative or monitoring issue. Reported in the annual water quality report.
Source: EPA Safe Drinking Water Information System (SDWIS) · Updated quarterly
Water Utility Details
CLEARLAKE OAKS COUNTY WATER DISTRICT
Population Served
2,359
Water Source
Surface Water
System ID
CA1710001
Frequently Asked Questions About Clearlake Oak Water
Is Clearlake Oak tap water safe to drink?
Clearlake Oak, California tap water receives a grade of B (67/100), which is considered good. Out of 9 contaminants tested, 1 exceed EPA maximum contaminant levels (MCLs) and 1 exceed health guidelines (MCLGs). While the water meets federal standards, some residents may still choose to use a filter for additional peace of mind.
What contaminants are in Clearlake Oak's water?
Of the 9 contaminants tested in Clearlake Oak's water supply, the most notable include Copper (90th percentile). 1 contaminant(s) exceed EPA legal limits (MCLs). 1 contaminant(s) exceed EPA health goals (MCLGs), which are non-enforceable targets set at levels with no known health risk.
Does Clearlake Oak have any water quality violations?
Yes, Clearlake Oak has 9 EPA violation(s) on record, with the most recent in 2023. Violation types include MCL, MR, TT. 4 of these are health-based violations, which are the most serious category.
Do I need a water filter in Clearlake Oak?
Based on EPA data, using a water filter in Clearlake Oak is recommended. 1 contaminant(s) exceed legal limits. An NSF-certified filter — such as a reverse osmosis or activated carbon system — can effectively reduce many common contaminants. Choose a filter certified to remove the specific contaminants found in your area.
Where does Clearlake Oak's tap water come from?
Clearlake Oak's drinking water is sourced from surface water and supplied by CLEARLAKE OAKS COUNTY WATER DISTRICT. The system serves approximately 2,359 people. Surface water sources include rivers, lakes, and reservoirs.
How often is Clearlake Oak's water tested?
Under the Safe Drinking Water Act (SDWA), water utilities are required to regularly test for over 90 contaminants. Testing frequency varies by contaminant — some are tested monthly, others quarterly or annually. Clearlake Oak's water systems must report results to the EPA and publish an annual Consumer Confidence Report (CCR). The data on this page reflects the latest available EPA testing data.
How does Clearlake Oak's water compare to other cities in California?
Clearlake Oak's water quality score of 67/100 earns a grade of B, which is considered good. This is an above-average score compared to many cities nationwide. Visit our California state page to see how all cities in the state compare.
What should I do if I'm concerned about Clearlake Oak's water quality?
If you have concerns about Clearlake Oak's tap water, consider these steps: (1) Request your utility's annual Consumer Confidence Report for detailed local data. (2) Get your water independently tested through a state-certified laboratory. (3) Consider an NSF-certified water filter rated for the contaminants found in your area. (4) Contact your water utility (CLEARLAKE OAKS COUNTY WATER DISTRICT) with specific questions. (5) Report water quality issues to your state drinking water program or the EPA Safe Drinking Water Hotline at 800-426-4791.