Water Quality Report · Updated May 12, 2026
FAIRFAX COUNTY WATER AUTHORITY
FAIRFAX COUNTY WATER AUTHORITY delivers tap water graded D (55/100) by TapWaterSafety.org. The utility serves approximately 1,121,613 residents in HERNDON, Virginia using surface water. The most significant water quality concerns are: PFAS contamination; Haloacetic acids (HAA9) 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 703-289-6568.
Is HERNDON tap water safe to drink?
FAIRFAX COUNTY WATER AUTHORITY delivers tap water that earns a grade of D (55/100) from TapWaterSafety.org — a below-average rating, with multiple concerns including pfas contamination.
The utility serves 1,121,613 residents in HERNDON, drawing from surface water.
Public testing data identifies 15 contaminants in this water above EWG's health-based guidelines, including: Haloacetic acids (HAA9), Total trihalomethanes (TTHMs), Haloacetic acids (HAA5), Bromodichloromethane, Trichloroacetic acid, Chloroform, Dichloroacetic acid, Dibromochloromethane, Dibromoacetic acid, Nitrate, Nitrate and nitrite, Chromium (hexavalent), Perfluorooctanoic acid (PFOA), 6:2 Fluorotelomer Sulfonic Acid (6:2 FTSA), Perfluorooctane sulfonate (PFOS). 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 HERNDON residents
Top concerns in this water
Based on the most recent EPA and EWG data, these are the most significant water quality issues for FAIRFAX COUNTY WATER AUTHORITY.
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.
Haloacetic acids (HAA9) significantly above health guideline
Moderate concernHaloacetic acids (HAA9) detected at 26.6 ppb, 444x above the EWG health guideline of 0.06 ppb.
Total trihalomethanes (TTHMs) significantly above health guideline
Moderate concernTotal trihalomethanes (TTHMs) detected at 27.8 ppb, 186x above the EWG health guideline of 0.15 ppb.
Haloacetic acids (HAA5) significantly above health guideline
Moderate concernHaloacetic acids (HAA5) detected at 16.4 ppb, 164x above the EWG health guideline of 0.1 ppb.
Contact FAIRFAX COUNTY WATER AUTHORITY
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 HERNDON
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 55/100 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 |
|---|---|---|---|---|---|---|---|---|
| Haloacetic acids (HAA9) Disinfection byproduct |
26.6 ppb | 0.06 | — | — | — | — | — | 444× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
27.8 ppb | 0.15 | 80.0 | 100 | — | — | — | 186× over |
| Haloacetic acids (HAA5) Disinfection byproduct |
16.4 ppb | 0.1 | 60.0 | 60 | — | — | — | 164× over |
| Bromodichloromethane Disinfection byproduct |
6.59 ppb | 0.06 | — | — | — | — | — | 110× over |
| Trichloroacetic acid Disinfection byproduct |
6.41 ppb | 0.1 | — | — | — | — | — | 64× over |
| Chloroform Disinfection byproduct |
17.7 ppb | 0.4 | — | — | — | — | — | 44× over |
| Dichloroacetic acid Disinfection byproduct |
8.72 ppb | 0.2 | — | — | — | — | — | 44× over |
| Dibromochloromethane Disinfection byproduct |
3.3 ppb | 0.1 | — | — | — | — | — | 33× over |
| Dibromoacetic acid Disinfection byproduct |
0.703 ppb | 0.03 | — | — | — | — | — | 23× over |
| Nitrate Inorganic |
1.12 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 8.0× over |
| Nitrate and nitrite Inorganic |
1.12 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 8.0× over |
| Chromium (hexavalent) Heavy metal |
0.103 ppb | 0.02 | — | — | — | — | — | 5.2× over |
| Perfluorooctanoic acid (PFOA) PFAS |
0.417 ppt | 0.09 | 4.0 | 100 | 100 | 0.007 | — | 4.6× over |
| 6:2 Fluorotelomer Sulfonic Acid (6:2 FTSA) Other |
3.17 ppt | 1.0 | — | — | — | — | — | 3.2× over |
| Perfluorooctane sulfonate (PFOS) PFAS |
0.392 ppt | 0.3 | 4.0 | 100 | 100 | 1 | — | 1.3× over |
| Chlorate Disinfection byproduct |
184.1 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Bromoform Disinfection byproduct |
0.269 ppb | 0.5 | — | — | — | — | — | Below guideline |
| Radium, combined (-226 and -228) Radiological |
0.02 pCi/L | 0.05 | 5.0 | — | — | — | — | Below guideline |
| Barium Heavy metal |
31.1 ppb | 700.0 | 2000.0 | — | 1300 | 2000 | — | Below guideline |
| Aluminum Heavy metal |
10.2 ppb | 600.0 | — | 200 | — | 600 | — | Below guideline |
| Vanadium Other |
0.347 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Monochloroacetic acid Disinfection byproduct |
0.324 ppb | 53.0 | — | — | — | — | — | Below guideline |
| Perfluoropentanoic Acid (PFPeA) PFAS |
2.88 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Molybdenum Other |
0.114 ppb | 40.0 | — | — | — | — | — | Below guideline |
| Perfluorohexanoic Acid (PFHxA) PFAS |
2.71 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Manganese Heavy metal |
0.0881 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Perfluorobutanoic Acid (PFBA) PFAS |
0.8 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Perfluorobutane sulfonate (PFBS) PFAS |
0.725 ppt | 2000.0 | — | — | — | — | — | Below guideline |
| Perfluoroheptanoic acid (PFHPA) PFAS |
0.325 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
0.127 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.674 ppm | — | 4.0 | 1.5 | 1.5 | — | — | Below guideline |
| Nitrite Inorganic |
0.000957 ppm | — | 1.0 | — | — | — | — | 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.
FAIRFAX COUNTY WATER AUTHORITY service area
This water system serves 1 community in Fairfax County, Virginia. Click any city for its dedicated tap water quality page.
Find the right filter for HERNDON water
Browse filter categories by water-quality concern. Each option below is NSF-certified for the matched contaminant type.