Water Quality in Costa Mesa, CA: 84 Violations — Grade C
Grade C · Score 55/100 · 3 water systems · Updated 2026-05-03
Costa Mesa'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
Costa Mesa in CA has 84 EPA water violations documented — the compliance history below covers what was flagged and which local systems are associated with each finding.
Water Quality by ZIP Code in Costa Mesa
Water quality varies across Costa Mesa's 3 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | Grade | Score | Violations | Health | |
|---|---|---|---|---|---|
| 92626 | D | 52 | 28 | 16 | View report → |
| 92628 | C | 55 | 28 | 16 | View report → |
| 92627 | C | 57 | 28 | 16 | View report → |
Violation Trend
EPA violations recorded for water systems serving Costa Mesa.
Water Quality Overview
Costa Mesa, California receives a water quality grade of C with an overall score of 55 out of 100, based on EPA compliance data from the Safe Drinking Water Information System (SDWIS).
The 3 water systems serving Costa Mesa have accumulated 84 EPA violations, including 48 health-based violations. These violations are tracked across 3 ZIP codes serving approximately 110,450 people.
What Grade C Means
A grade of C indicates moderate compliance issues. Costa Mesa'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
Lead testing data for Costa Mesa is currently being collected. The EPA requires all community water systems to test for lead under the Lead and Copper Rule.
With 78% of homes built before 1986, Costa Mesa 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.
Water Systems Serving Costa Mesa
Costa Mesa is served by 3 community water systems regulated under the Safe Drinking Water Act. These systems collectively serve approximately 110,450 people across 3 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
The EPA has taken 3 enforcement actions against water systems serving Costa Mesa. Enforcement actions range from informal compliance assistance to formal orders and penalties.
How to Check Your Water in Costa Mesa
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
Violation Trend Over Time
Year-by-year EPA violations recorded for water systems serving Costa Mesa:
| Year | Total Violations | Health-Based |
|---|---|---|
| 2022 | 3 | 3 |
| 2023 | 21 | 21 |
| 2024 | 21 | 21 |
Violations have increased from 3 in 2022 to 21 in 2024. This trend warrants monitoring.
EPA Enforcement History
The EPA and state regulators have taken 1 enforcement action against water systems serving Costa Mesa. Recent actions:
| Date | Action Type |
|---|---|
| 2025-03-19 | State Filed Suit |
Enforcement actions range from informal compliance assistance to formal orders and penalties. The most recent action was on 2025-03-19.
Costa Mesa vs. Nearby California Cities
How Costa Mesa's water quality compares to similar cities in California:
| City | Grade | Violations | Systems | Population |
|---|---|---|---|---|
| Costa Mesa | C | 84 | 3 | 110,450 |
| Azusa | B | 3 | 3 | 110,159 |
| Santa Maria | C | 25 | 5 | 109,974 |
| Highland | B | 0 | 1 | 108,629 |
Recommended Water Filters for Costa Mesa
Based on contaminants detected in Costa Mesa's water supply, these filter types are recommended:
Granular Activated Carbon (GAC, whole-house or under-sink)
- Removes: Chlorine Residual
- Effectiveness: 95-99%
- Cost range: $100–$600
- Certification: NSF/ANSI 42
- Recommended products:
- Aquasana AQ-5200
- Waterdrop Chubby Pitcher
- Berkey Travel
Water Quality by ZIP Code in Costa Mesa
Water quality varies across Costa Mesa's ZIP codes. The table below shows the worst-scoring and best-scoring areas:
Common Questions About Costa Mesa Water
These are the most common questions residents search for about water quality in Costa Mesa, California:
Is Costa Mesa water hard or soft? Water hardness varies by source. Costa Mesa's 3 water systems use multiple sources. Check your ZIP code report for specific hardness data.
Can I drink Costa Mesa tap water? Costa Mesa's water receives a grade of C (55/100). There are 48 health-based violations — consider filtration.
What is the best water filter for Costa Mesa? Based on detected contaminants, a granular activated carbon (gac, whole-house or under-sink) filter is most recommended. See our Water Filter Matcher for personalized recommendations.
Costa Mesa vs. California Average
Understanding how Costa Mesa 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 Costa Mesa.
ZIP Codes in Costa Mesa
Costa Mesa spans 3 ZIP codes. The ZIP with the lowest water quality score is 92626. 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.