Tap Water Quality Report
Tap water quality in COSTA MESA, California
Tap water in COSTA MESA, California receives a grade of C (71/100) from TapWaterSafety.org. It's served by MESA WATER DISTRICT. The most significant water quality concerns are: Arsenic significantly above health guideline; Haloacetic acids (HAA5) significantly above health guideline; Haloacetic acids (HAA9) significantly above health guideline. Data sources: EPA SDWIS, EPA ECHO, EWG Tap Water Database.
What's in COSTA MESA's tap water
Top water quality concerns identified by the EPA and Environmental Working Group across the utility serving COSTA MESA.
Arsenic significantly above health guideline
Moderate concernArsenic detected at 1.64 ppb, 409x above the EWG health guideline of 0.004 ppb.
Haloacetic acids (HAA5) significantly above health guideline
Moderate concernHaloacetic acids (HAA5) detected at 36.2 ppb, 362x above the EWG health guideline of 0.1 ppb.
Haloacetic acids (HAA9) significantly above health guideline
Moderate concernHaloacetic acids (HAA9) detected at 5.62 ppb, 94x above the EWG health guideline of 0.06 ppb.
EPA compliance record
Official U.S. EPA records for MESA WATER DISTRICT (system ID CA3010004) for the last 3 years. Checked 2026-10-07.
Source: U.S. EPA Enforcement and Compliance History Online (ECHO), from the Safe Drinking Water Information System. See EPA's full report.
Recommended filters for COSTA MESA
Filters matched to the specific contaminants in COSTA MESA's water supply.
Reverse osmosis certified for arsenic (NSF/ANSI 58)
$429-$599Reverse osmosis certified under NSF/ANSI 58 for arsenic is the most reliable home option.
Carbon filter certified for VOCs (NSF/ANSI 53)
$180-$599Activated carbon is effective for disinfection byproducts. Look for NSF/ANSI 53 VOC reduction.
Disclosure: TapWaterSafety earns a commission from purchases made through these links. This does not influence our scoring methodology or filter selection.
All contaminants detected in COSTA MESA's tap water
Every contaminant identified, compared side-by-side against US EPA legal limits, the EU Drinking Water Directive (2020/2184), WHO Guidelines, and California's Public Health Goal. Why we show multiple standards →
| Contaminant | Detected | EWG US health-based |
EPA US legal |
EU DWD Europe |
WHO global |
CA PHG strictest US |
Tested sample year |
Status |
|---|---|---|---|---|---|---|---|---|
| Arsenic Heavy metal |
1.64 ppb | 0.004 | 10.0 | 10 | 10 | 0.004 | — | 409× over |
| Haloacetic acids (HAA5) Disinfection byproduct |
36.2 ppb | 0.1 | 60.0 | 60 | — | — | — | 362× over |
| Haloacetic acids (HAA9) Disinfection byproduct |
5.62 ppb | 0.06 | — | — | — | — | — | 94× over |
| Dibromoacetic acid Disinfection byproduct |
1.6 ppb | 0.03 | — | — | — | — | — | 53× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
6.55 ppb | 0.15 | 80.0 | 100 | — | — | — | 44× over |
| Bromodichloromethane Disinfection byproduct |
0.882 ppb | 0.06 | — | — | — | — | — | 15× over |
| Dibromochloromethane Disinfection byproduct |
1.45 ppb | 0.1 | — | — | — | — | — | 15× over |
| Bromoform Disinfection byproduct |
3.54 ppb | 0.5 | — | — | — | — | — | 7.1× over |
| Chromium (hexavalent) Heavy metal |
0.136 ppb | 0.02 | — | — | — | — | — | 6.8× over |
| 1,4-Dioxane Semi-volatile organic compound |
1.72 ppb | 0.35 | — | — | 50 | 1 | — | 4.9× over |
| Nitrate and nitrite Inorganic |
0.515 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 3.7× over |
| Nitrate Inorganic |
0.414 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 3.0× over |
| Chloroform Disinfection byproduct |
0.727 ppb | 0.4 | — | — | — | — | — | 1.8× over |
| Uranium Radiological |
0.76 pCi/L | 0.43 | 20.0 | 30 | 30 | 0.43 | — | 1.8× over |
| Radium, combined (-226 and -228)* Radiological |
0.07 pCi/L | 0.05 | 5.0 | — | — | — | — | 1.4× over |
| Chlorate Disinfection byproduct |
133.3 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Vanadium Other |
4.29 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Aluminum* Heavy metal |
77.5 ppb | 600.0 | — | 200 | — | 600 | — | Below guideline |
| Molybdenum Other |
4.81 ppb | 40.0 | — | — | — | — | — | Below guideline |
| Dichloroacetic acid Disinfection byproduct |
0.0125 ppb | 0.2 | — | — | — | — | — | Below guideline |
| Barium* Heavy metal |
36.7 ppb | 700.0 | 2000.0 | — | 1300 | 2000 | — | Below guideline |
| Manganese Heavy metal |
2.09 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Strontium Radiological |
0.478 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Bromide Other |
298.5 ppb | — | — | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.519 ppm | — | 4.0 | 1.5 | 1.5 | — | — | Below guideline |
| Germanium Other |
0.207 ppb | — | — | — | — | — | — | Below guideline |
| Lithium Other |
4.34 ppb | — | — | — | — | — | — | Below guideline |
All values in the unit of the detected level. Red cells indicate the detected level exceeds that standard. Some contaminants have limits in some jurisdictions but not others (shown as —). The "Tested" column shows the year each contaminant sample was collected.
Sources: US EPA, EU Drinking Water Directive 2020/2184, WHO Guidelines, California OEHHA PHGs, EWG Tap Water Database.
Treatment plant contact info
For service issues, water quality concerns, or to request a Consumer Confidence Report from MESA WATER DISTRICT.