Water Quality in Thousand Oaks, CA: No Violations — Grade C
Grade C · Score 66/100 · 2 water systems · Updated 2026-05-03
Thousand Oaks's water has moderate compliance issues. Residents in affected areas should consider filtration.
Data: EPA Safe Drinking Water Information System (SDWIS) Last verified: 2026-05-03
What does the EPA compliance record show for Thousand Oaks, CA? Zero violations documented across 2 water systems, with all health-based and monitoring thresholds met across all available federal records.
Water Quality by ZIP Code in Thousand Oaks
Water quality varies across Thousand Oaks's 4 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | Grade | Score | Violations | Health | |
|---|---|---|---|---|---|
| 91360 | C | 65 | 0 | 0 | View report → |
| 91362 | C | 65 | 0 | 0 | View report → |
| 91358 | C | 66 | 0 | 0 | View report → |
| 91363 | B | 83 | 0 | 0 | View report → |
Water Quality Overview
Thousand Oaks, California receives a water quality grade of C with an overall score of 66 out of 100, based on EPA compliance data from the Safe Drinking Water Information System (SDWIS).
No EPA violations have been recorded for the 2 water systems serving Thousand Oaks. This is a positive indicator, though it does not guarantee the absence of all contaminants — some substances (like PFAS) are not yet fully regulated.
What Grade C Means
A grade of C indicates moderate compliance issues. Thousand Oaks's water systems have some violations that warrant attention. While the water may still be safe for most people, residents in affected ZIP codes should consider additional testing or filtration.
Lead Levels
The average 90th percentile lead level across Thousand Oaks water systems is 0.0025 mg/L — within EPA limits. No ZIP codes exceed the EPA lead action level.
With 71% of homes built before 1986, Thousand Oaks has a higher-than-average risk of lead from older plumbing. Lead solder was banned in 1986, and homes built before this date may have lead in pipes, solder joints, or fixtures.
Radon Risk
Thousand Oaks is in EPA Radon Zone 1 (High risk). The EPA recommends all homes in Zone 1 areas be tested for radon. Radon is the second leading cause of lung cancer after smoking.
Water Systems Serving Thousand Oaks
Thousand Oaks is served by 2 community water systems regulated under the Safe Drinking Water Act. These systems collectively serve approximately 53,157 people across 4 ZIP codes.
Each water system is identified by a Public Water System ID (PWSID) and is required to:
- Test for over 90 regulated contaminants on a regular schedule
- Report results to the EPA and state regulators
- Issue an annual Consumer Confidence Report (CCR) to all customers
- Take corrective action when violations occur
How to Check Your Water in Thousand Oaks
Enter your ZIP code on ZipCheckup to see your specific water system data, including contaminant levels, violation history, and safety scores
Request your CCR — your water utility must provide an annual Consumer Confidence Report with detailed test results for all monitored contaminants
Get a home test — certified kits cost $20–$50 and test for lead, bacteria, and common contaminants. Professional lab tests ($150–$400) cover a broader panel
Consider filtration — NSF-certified filters can remove specific contaminants. Reverse osmosis removes the broadest range; activated carbon is effective for chlorine and many organics
Check for advisories — monitor your local utility website and local news for boil water advisories or system alerts
Thousand Oaks vs. Nearby California Cities
How Thousand Oaks's water quality compares to similar cities in California:
| City | Grade | Violations | Systems | Population |
|---|---|---|---|---|
| Thousand Oaks | C | 0 | 2 | 53,157 |
| Newbury Park | D | 0 | 1 | 53,157 |
| Oak Park | D | 0 | 1 | 53,157 |
| Montebello | B | 6 | 4 | 53,110 |
Water Quality by ZIP Code in Thousand Oaks
Water quality varies across Thousand Oaks's ZIP codes. The table below shows the worst-scoring and best-scoring areas:
| ZIP Code | Score | Grade | Violations | Health-Based |
|---|---|---|---|---|
| 91360 | 65 | C | 0 | 0 |
| 91362 | 65 | C | 0 | 0 |
| 91358 | 66 | C | 0 | 0 |
| 91363 | 83 | B | 0 | 0 |
Common Questions About Thousand Oaks Water
These are the most common questions residents search for about water quality in Thousand Oaks, California:
Is Thousand Oaks water hard or soft? Water hardness varies by source. Thousand Oaks's 2 water systems use multiple sources. Check your ZIP code report for specific hardness data.
Can I drink Thousand Oaks tap water? Thousand Oaks's water receives a grade of C (66/100). No health-based violations have been recorded, but home testing is always recommended.
What is the best water filter for Thousand Oaks? A NSF/ANSI 53-certified filter for lead removal is a good general choice. See our Water Filter Matcher for personalized recommendations.
Thousand Oaks vs. California Average
Understanding how Thousand Oaks compares to the broader California average helps contextualize your local water quality. Factors like water source, treatment methods, and infrastructure age all contribute to differences between cities in the same state.
To see how individual neighborhoods compare, check the ZIP code reports below — water quality can vary significantly even within Thousand Oaks.
ZIP Codes in Thousand Oaks
Thousand Oaks spans 4 ZIP codes. Each ZIP code has its own water quality profile based on the specific water system serving that area. Check each ZIP code for detailed contaminant data, violation history, and system information.
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Lead/copper: EPA Lead and Copper Rule sampling data
- Radon: EPA Map of Radon Zones
- Enforcement: EPA ECHO database
- Filter recommendations: NSF/ANSI certified products
Updated daily.