Water Quality Report · Updated May 12, 2026
ALAMEDA COUNTY WATER DISTRICT
ALAMEDA COUNTY WATER DISTRICT delivers tap water graded D (56/100) by TapWaterSafety.org. The utility serves approximately 344,000 residents in FREMONT, California using surface water. 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. For questions, the utility can be reached at 510-668-4200.
Is FREMONT tap water safe to drink?
ALAMEDA COUNTY WATER DISTRICT delivers tap water that earns a grade of D (56/100) from TapWaterSafety.org — a below-average rating, with multiple concerns including pfas contamination.
The utility serves 344,000 residents in FREMONT, drawing from surface water.
Public testing data identifies 10 contaminants in this water above EWG's health-based guidelines, including: Perfluorohexane sulfonate (PFHXS), Total trihalomethanes (TTHMs), Haloacetic acids (HAA5), Haloacetic acids (HAA9), Bromate, Perfluorooctane sulfonate (PFOS), Chromium (hexavalent), Nitrate and nitrite, Nitrate, Chlorate. 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.
Quick actions for FREMONT residents
Top concerns in this water
Based on the most recent EPA and EWG data, these are the most significant water quality issues for ALAMEDA COUNTY WATER DISTRICT.
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.
Contact ALAMEDA COUNTY 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 FREMONT
Filters matched to the specific contaminants in this water supply.
Reverse Osmosis or NSF P473 certified carbon
$80-$750Activated carbon and RO are the only technologies proven to remove PFAS at certified levels.
Carbon block (NSF/ANSI 42 + 53)
$40-$750Activated carbon is highly effective for disinfection byproducts like TTHM and HAA5.
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 56/100 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 |
|---|---|---|---|---|---|---|---|---|
| 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 (4th ed.), California OEHHA PHGs, EWG Tap Water Database.
ALAMEDA COUNTY WATER DISTRICT service area
This water system serves 1 community in Alameda County, California. Click any city for its dedicated tap water quality page.
Find the right filter for FREMONT water
Browse filter categories by water-quality concern. Each option below is NSF-certified for the matched contaminant type.