Tap Water Quality Report
Tap water quality in MERCED, California
Tap water in MERCED, California receives a grade of D (62/100) from TapWaterSafety.org. It's served by CITY OF MERCED. The most significant water quality concerns are: PFAS contamination; Perfluorohexane sulfonate (PFHXS) significantly above health guideline; Arsenic significantly above health guideline; Haloacetic acids (HAA5) significantly above health guideline. Data sources: EPA SDWIS, EPA ECHO, EWG Tap Water Database.
What's in MERCED's tap water
Top water quality concerns identified by the EPA and Environmental Working Group across the utility serving MERCED.
PFAS contamination
Severe concernPerfluorooctanoic acid (PFOA), Perfluorooctane sulfonate (PFOS) detected. PFAS are persistent chemicals linked to cancer and immune effects with no known safe exposure threshold.
Perfluorohexane sulfonate (PFHXS) significantly above health guideline
Moderate concernPerfluorohexane sulfonate (PFHXS) detected at 1.22 ppt, 1221x above the EWG health guideline of 0.001 ppt.
Arsenic significantly above health guideline
Moderate concernArsenic detected at 3.34 ppb, 836x 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.
EPA compliance record
Official U.S. EPA records for CITY OF MERCED (system ID CA2410009) 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 MERCED
Filters matched to the specific contaminants in MERCED's water supply.
Filter certified for PFOA/PFOS (NSF/ANSI 53 or 58)
$180-$750Reverse osmosis and some carbon block filters reduce PFAS. Look for certification to NSF/ANSI 53 or 58 for PFOA/PFOS.
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 MERCED'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 |
|---|---|---|---|---|---|---|---|---|
| Perfluorohexane sulfonate (PFHXS) PFAS |
1.22 ppt | 0.001 | 10.0 | — | — | — | — | 1221× over |
| Arsenic Heavy metal |
3.34 ppb | 0.004 | 10.0 | 10 | 10 | 0.004 | — | 836× over |
| Haloacetic acids (HAA5) Disinfection byproduct |
36.2 ppb | 0.1 | 60.0 | 60 | — | — | — | 362× over |
| Chromium (hexavalent) Heavy metal |
3.63 ppb | 0.02 | — | — | — | — | — | 181× over |
| Nitrate and nitrite Inorganic |
2.55 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 18× over |
| Nitrate Inorganic |
2.32 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 17× over |
| Perfluorooctanoic acid (PFOA) PFAS |
0.321 ppt | 0.09 | 4.0 | 100 | 100 | 0.007 | — | 3.6× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
0.283 ppb | 0.15 | 80.0 | 100 | — | — | — | 1.9× over |
| Perfluorooctane sulfonate (PFOS) PFAS |
0.543 ppt | 0.3 | 4.0 | 100 | 100 | 1 | — | 1.8× over |
| Bromodichloromethane Disinfection byproduct |
0.107 ppb | 0.06 | — | — | — | — | — | 1.8× over |
| Uranium Radiological |
0.5 pCi/L | 0.43 | 20.0 | 30 | 30 | 0.43 | — | 1.2× over |
| Tetrachloroethylene (perchloroethylene) Volatile organic compound |
0.0672 ppb | 0.06 | 5.0 | — | — | — | — | 1.1× over |
| Vanadium Other |
21.9 ppb | 21.0 | — | — | — | — | — | 1.0× over |
| Haloacetic acids (HAA9) Disinfection byproduct |
0.05 ppb | 0.06 | — | — | — | — | — | Below guideline |
| Dibromochloromethane Disinfection byproduct |
0.0833 ppb | 0.1 | — | — | — | — | — | Below guideline |
| Radium, combined (-226 and -228) Radiological |
0.03 pCi/L | 0.05 | 5.0 | — | — | — | — | Below guideline |
| Chlorate Disinfection byproduct |
112.9 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Barium Heavy metal |
231.3 ppb | 700.0 | 2000.0 | — | 1300 | 2000 | — | Below guideline |
| 1,2,3-Trichloropropane Other |
0.000196 ppb | 0.0007 | — | — | — | — | — | Below guideline |
| Chloroform Disinfection byproduct |
0.0417 ppb | 0.4 | — | — | — | — | — | Below guideline |
| Bromoform Disinfection byproduct |
0.0467 ppb | 0.5 | — | — | — | — | — | Below guideline |
| Molybdenum Other |
1.44 ppb | 40.0 | — | — | — | — | — | Below guideline |
| 1,2-Dichloroethane Volatile organic compound |
0.00769 ppb | 0.4 | 5.0 | — | — | — | — | Below guideline |
| 1,4-Dioxane Semi-volatile organic compound |
0.0055 ppb | 0.35 | — | — | 50 | 1 | — | Below guideline |
| Manganese Heavy metal |
1.24 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Trichloroethylene Volatile organic compound |
0.00171 ppb | 0.4 | 5.0 | 10 | 20 | 1.7 | — | Below guideline |
| Perfluorohexanoic Acid (PFHxA) PFAS |
0.287 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
0.368 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Chlorodifluoromethane Other |
0.0128 ppb | — | — | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.1 ppm | — | 4.0 | 1.5 | 1.5 | — | — | Below guideline |
| o-toluidine Other |
0.0019 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 CITY OF MERCED.