Water Quality Report · Updated October 07, 2026
MESA WATER DISTRICT
MESA WATER DISTRICT delivers tap water graded C (71/100) by TapWaterSafety.org. The utility serves approximately 110,000 residents in COSTA MESA, California using surface water (purchased). 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. For questions, the utility can be reached at 949-207-5470.
Is COSTA MESA tap water safe to drink?
MESA WATER DISTRICT delivers tap water that earns a grade of C (71/100) from TapWaterSafety.org — an average rating, with several contaminants above health guidelines but generally compliant with US legal limits.
The utility serves 110,000 residents in COSTA MESA, drawing from surface water (purchased).
Public testing data identifies 15 contaminants in this water above EWG's health-based guidelines, including: Arsenic, Haloacetic acids (HAA5), Haloacetic acids (HAA9), Dibromoacetic acid, Total trihalomethanes (TTHMs), Bromodichloromethane, Dibromochloromethane, Bromoform, Chromium (hexavalent), 1,4-Dioxane, Nitrate and nitrite, Nitrate, Chloroform, Uranium, Radium, combined (-226 and -228)*. For most residents, a properly certified home filter at the kitchen tap is the most cost-effective way to reduce exposure to whatever's in your water. See our filter recommendations below, matched specifically to this utility's contaminant profile.
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.
Quick actions for COSTA MESA residents
Top concerns in this water
Based on the most recent EPA and EWG data, these are the most significant water quality issues for MESA WATER DISTRICT.
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.
Contact MESA WATER DISTRICT
Reach the utility directly for service issues, water quality concerns, or to request your Consumer Confidence Report.
General Contact
Treatment Plant
Recommended water filters for COSTA MESA
Filters matched to the specific contaminants in this 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.
Score breakdown
This utility's overall score of 71/100 breaks down across five weighted components. Read the full methodology →
Contaminants detected — international standards comparison
Every contaminant detected, compared side-by-side against US EPA legal limits, the EU Drinking Water Directive (2020/2184), WHO Guidelines, and California's Public Health Goal (the strictest US benchmark). 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 (4th ed.), California OEHHA PHGs, EWG Tap Water Database.
MESA WATER DISTRICT service area
This water system serves 1 community in Orange County, California. Click any city for its dedicated tap water quality page.
Find the right filter for COSTA MESA water
Browse filter categories by water-quality concern. Each option below is NSF-certified for the matched contaminant type.