Tap Water Quality Report
Tap water quality in Fremont, California
Tap water in Fremont, California receives a grade of C (70/100) from TapWaterSafety.org. It's served by ALAMEDA COUNTY WATER DISTRICT. The most significant water quality concerns are: PFAS contamination; Perfluorohexane sulfonate (PFHXS) significantly above health guideline; Total trihalomethanes (TTHMs) significantly above health guideline; Haloacetic acids (HAA5) significantly above health guideline. Data sources: EPA SDWIS, EPA ECHO, EWG Tap Water Database.
What's in Fremont's tap water
Top water quality concerns identified by the EPA and Environmental Working Group across the utility serving Fremont.
PFAS contamination
Severe concernPerfluorooctane sulfonate (PFOS), Perfluorooctanoic acid (PFOA) 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 1.38 ppt, 1381x above the EWG health guideline of 0.001 ppt.
Total trihalomethanes (TTHMs) significantly above health guideline
Moderate concernTotal trihalomethanes (TTHMs) detected at 41.3 ppb, 276x above the EWG health guideline of 0.15 ppb.
Haloacetic acids (HAA5) significantly above health guideline
Moderate concernHaloacetic acids (HAA5) detected at 27.3 ppb, 273x above the EWG health guideline of 0.1 ppb.
EPA compliance record
Official U.S. EPA records for ALAMEDA COUNTY WATER DISTRICT (system ID CA0110001) 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 Fremont
Filters matched to the specific contaminants in Fremont'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.
Carbon filter certified for VOCs (NSF/ANSI 53)
$180-$599Activated carbon is effective for disinfection byproducts like TTHM. Look for NSF/ANSI 53 VOC or chloroform 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 Fremont'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 |
1.38 ppt | 0.001 | 10.0 | — | — | — | — | 1381× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
41.3 ppb | 0.15 | 80.0 | 100 | — | — | — | 276× over |
| Haloacetic acids (HAA5) Disinfection byproduct |
27.3 ppb | 0.1 | 60.0 | 60 | — | — | — | 273× over |
| Haloacetic acids (HAA9) Disinfection byproduct |
12.6 ppb | 0.06 | — | — | — | — | — | 209× over |
| Bromate Disinfection byproduct |
1.18 ppb | 0.1 | 10.0 | 10 | 10 | 0.1 | — | 12× over |
| Perfluorooctane sulfonate (PFOS) PFAS |
2.55 ppt | 0.3 | 4.0 | 100 | 100 | 1 | — | 8.5× over |
| Chromium (hexavalent) Heavy metal |
0.136 ppb | 0.02 | — | — | — | — | — | 6.8× over |
| Nitrate and nitrite Inorganic |
0.332 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 2.4× over |
| Nitrate Inorganic |
0.328 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 2.3× over |
| Chlorate Disinfection byproduct |
222.9 ppb | 210.0 | — | — | — | — | — | 1.1× over |
| Perfluorooctanoic acid (PFOA) PFAS |
0.059 ppt | 0.09 | 4.0 | 100 | 100 | 0.007 | — | Below guideline |
| Vanadium Other |
0.432 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Manganese Heavy metal |
1.23 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Molybdenum Other |
0.396 ppb | 40.0 | — | — | — | — | — | Below guideline |
| Perfluorobutanoic Acid (PFBA) PFAS |
1.04 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Perfluorobutane sulfonate (PFBS) PFAS |
1.06 ppt | 2000.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
0.204 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Perfluorohexanoic Acid (PFHxA) PFAS |
0.055 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Chlorodifluoromethane Other |
0.018 ppb | — | — | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.752 ppm | — | 4.0 | 1.5 | 1.5 | — | — | 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 ALAMEDA COUNTY WATER DISTRICT.