Herndon, Virginia Tap Water Quality Report
Serving utility: Fairfax County Water Authority
Updated March 2026 • Data from EWG Tap Water Database & EPA SDWIS
High Priority Concerns
Herndon tap water has 15 contaminants exceeding EWG health guidelines, including Haloacetic acids (HAA9), Total trihalomethanes (TTHMs), Haloacetic acids (HAA5). Additionally, 15 known or suspected carcinogens were detected, including Haloacetic acids (HAA9), Total trihalomethanes (TTHMs), Haloacetic acids (HAA5).
Water Provider Information
Contaminants Detected
| Contaminant | Detected Level | EWG Guideline | Legal Limit | Status |
|---|---|---|---|---|
| Haloacetic acids (HAA9) carcinogen | 26.60 ppb | 0.06 ppb | No legal limit | Above guideline |
| Total trihalomethanes (TTHMs) carcinogen | 27.80 ppb | 0.15 ppb | 80 ppb | Above guideline |
| Haloacetic acids (HAA5) carcinogen | 16.40 ppb | 0.10 ppb | 60 ppb | Above guideline |
| Bromodichloromethane carcinogen | 6.59 ppb | 0.06 ppb | No legal limit | Above guideline |
| Trichloroacetic acid carcinogen | 6.41 ppb | 0.10 ppb | No legal limit | Above guideline |
| Chloroform carcinogen | 17.70 ppb | 0.40 ppb | No legal limit | Above guideline |
| Dichloroacetic acid carcinogen | 8.72 ppb | 0.20 ppb | No legal limit | Above guideline |
| Dibromochloromethane carcinogen | 3.30 ppb | 0.10 ppb | No legal limit | Above guideline |
| Dibromoacetic acid | 0.70 ppb | 0.03 ppb | No legal limit | Above guideline |
| Nitrate carcinogen | 1.12 ppm | 0.14 ppm | 10 ppm | Above guideline |
| Nitrate and nitrite carcinogen | 1.12 ppm | 0.14 ppm | 10 ppm | Above guideline |
| Chromium (hexavalent) carcinogen | 0.10 ppb | 0.02 ppb | No legal limit | Above guideline |
| Perfluorooctanoic acid (PFOA) carcinogen | 0.42 ppt | 0.09 ppt | 4 ppt | Above guideline |
| 6:2 Fluorotelomer Sulfonic Acid (6:2 FTSA) | 3.17 ppt | 1 ppt | No legal limit | Above guideline |
| Perfluorooctane sulfonate (PFOS) carcinogen | 0.39 ppt | 0.30 ppt | 4 ppt | Above guideline |
| Aluminum | 10.20 ppb | 600 ppb | No legal limit | Below guideline |
| Barium | 31.10 ppb | 700 ppb | 2,000 ppb | Below guideline |
| Bromoform carcinogen | 0.27 ppb | 0.50 ppb | No legal limit | Below guideline |
| Chlorate | 184.10 ppb | 210 ppb | No legal limit | Near guideline |
| Fluoride | 0.67 ppm | N/A | 4 ppm | Below guideline |
| Manganese | 0.09 ppb | 100 ppb | No legal limit | Below guideline |
| Molybdenum | 0.11 ppb | 40 ppb | No legal limit | Below guideline |
| Monochloroacetic acid | 0.32 ppb | 53 ppb | No legal limit | Below guideline |
| Nitrite carcinogen | 0.00 ppm | N/A | 1 ppm | Below guideline |
| Perfluorobutane sulfonate (PFBS) | 0.72 ppt | 2,000 ppt | No legal limit | Below guideline |
| Perfluorobutanoic Acid (PFBA) | 0.80 ppt | 1,000 ppt | No legal limit | Below guideline |
| Perfluoroheptanoic acid (PFHPA) | 0.33 ppt | 1,000 ppt | No legal limit | Below guideline |
| Perfluorohexanoic Acid (PFHxA) | 2.71 ppt | 1,000 ppt | No legal limit | Below guideline |
| Perfluoropentanoic Acid (PFPeA) | 2.88 ppt | 1,000 ppt | No legal limit | Below guideline |
| Radium, combined (-226 and -228) | 0.02 pCi/L | 0.05 pCi/L | 5 pCi/L | Below guideline |
| Strontium | 0.13 ppb | 1,500 ppb | No legal limit | Below guideline |
| Vanadium | 0.35 ppb | 21 ppb | No legal limit | Below guideline |
Health Context
Haloacetic acids (HAA9) carcinogen
Exposure to elevated levels of this contaminant may pose health risks. See EWG and EPA guidelines for more information.
Total trihalomethanes (TTHMs) carcinogen
Exposure to elevated levels of this contaminant may pose health risks. See EWG and EPA guidelines for more information.
Haloacetic acids (HAA5) carcinogen
Exposure to elevated levels of this contaminant may pose health risks. See EWG and EPA guidelines for more information.
Bromodichloromethane carcinogen
Bromodichloromethane is a trihalomethane (THM) disinfection byproduct that damages liver and kidneys with chronic exposure. EPA classifies it as a probable human carcinogen based on animal carcinogenicity data.
Trichloroacetic acid carcinogen
Exposure to elevated levels of this contaminant may pose health risks. See EWG and EPA guidelines for more information.
Recommended Filtration for This Water
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Shop Hydrogen FlaskFrequently Asked Questions
Is Herndon tap water safe to drink?
Herndon tap water meets EPA legal standards for drinking water. However, 15 contaminants exceed stricter EWG health guidelines, and 15 known carcinogens were detected. While legally compliant, additional filtration is recommended for optimal safety.
What contaminants are in Herndon water?
A total of 32 contaminants were detected in Herndon tap water, including Haloacetic acids (HAA9), Total trihalomethanes (TTHMs). Of these, 15 exceed EWG health guidelines.
What's the best water filter for Herndon?
For Herndon tap water, we recommend a reverse osmosis (RO) system for drinking water — it removes up to 99.9% of contaminants including heavy metals, PFAS, and disinfection byproducts. For shower and bath water, a whole-home filtration system reduces chlorine and volatile organics.
Where does Herndon get its water?
Herndon tap water is provided by Fairfax County Water Authority, serving approximately 1,121,613 people. For detailed source water information, contact your local utility or visit the EPA's SDWIS database.
Nearby City Water Reports
Data sources: Environmental Working Group (EWG) Tap Water Database, U.S. EPA Safe Drinking Water Information System (SDWIS)
Last updated: March 2026
Methodology: Contaminant levels are compared against both EPA legal limits (Maximum Contaminant Levels) and EWG health guidelines, which are often stricter and based on the latest scientific research.
