What was found in Herndon's water
The level at the city's main supplier, the highest level anywhere in the city, the EPA limit for each, and where every figure comes from.
| Contaminant | Level vs EPA limit | Suppliers | Source |
|---|---|---|---|
| Nitrate-Nitrite | 1614 µg/L 16% of the EPA limit 10000 µg/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 1/2 | SYR4 |
| Nitrate | 1610 µg/L 16% of the EPA limit 10000 µg/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 1/2 | SYR4 |
| Fluoride | 800 µg/L 20% of the EPA limit 4000 µg/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 1/2 | SYR4 |
| Copper | 190 µg/L 15% of the EPA limit 1300 µg/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019
Highest in the city: 255.8 µg/L — HERNDON, TOWN OF · 24,601 people · 2017 | 2/2 | SYR4 |
| TTHM | 63.305 µg/L 79% of the EPA limit 80 µg/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 2/2 | SYR4 |
| Barium | 48.16 µg/L 2.4% of the EPA limit 2000 µg/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 1/2 | SYR4 |
| Chloroform | 47.57 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 2/2 | SYR4 |
| Total Haloacetic Acids (HAA5) | 40.7 µg/L 68% of the EPA limit 60 µg/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 2/2 | SYR4 |
| Dichloroacetic Acid | 22.115 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 2/2 | SYR4 |
| Nitrite | 20 µg/L 2% of the EPA limit 1000 µg/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 1/2 | SYR4 |
| Trichloroacetic Acid | 17.5 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 2/2 | SYR4 |
| Bromodichloromethane | 12.7 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 2/2 | SYR4 |
| Bromate | 8.9 µg/L 89% of the EPA limit 10 µg/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 1/2 | SYR4 |
| Dibromochloromethane | 6.6695 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019
Highest in the city: 8.644 µg/L — HERNDON, TOWN OF · 24,601 people · 2019 | 2/2 | SYR4 |
| Gross Beta Particle Activity | 5.55 pCi/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 1/2 | SYR4 |
| Monochloroacetic Acid | 3.737 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 2/2 | SYR4 |
| Lead | 1.09 µg/L 7.3% of the EPA limit 15 µg/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019
Highest in the city: 3.06 µg/L — HERNDON, TOWN OF · 24,601 people · 2017 | 2/2 | SYR4 |
| Gross Alpha, Excl. Radon And U | 3.01 pCi/L 20% of the EPA limit 15 pCi/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 1/2 | SYR4 |
| Dibromoacetic Acid | 2.329 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019
Highest in the city: 2.627 µg/L — HERNDON, TOWN OF · 24,601 people · 2019 | 2/2 | SYR4 |
| Bromoform | 1.41 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019
Highest in the city: 1.9985 µg/L — HERNDON, TOWN OF · 24,601 people · 2019 | 2/2 | SYR4 |
| Combined Radium (-226 And -228) | 0.6501 pCi/L 13% of the EPA limit 5 pCi/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 1/2 | SYR4 |
| Combined Uranium | 0.1120 µg/L 0.4% of the EPA limit 30 µg/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2019 | 1/2 | SYR4 |
| Atrazine | 0.0875 µg/L 2.9% of the EPA limit 3 µg/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2017 | 1/2 | SYR4 |
| Pfpea | 0.0215 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2025 | 2/2 | UCMR-5 |
| Pfba | 0.0176 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2025 | 2/2 | UCMR-5 |
| Pfhxa | 0.0171 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2025 | 2/2 | UCMR-5 |
| 6:2 Fts | 0.0101 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2025 | 1/2 | UCMR-5 |
| PFBS | 0.0081 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2025 | 1/2 | UCMR-5 |
| PFOA | 0.0074 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2025 | 1/2 | UCMR-5 |
| PFOS | 0.0057 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2025 | 1/2 | UCMR-5 |
| Pfhpa | 0.0056 µg/L No EPA limit set Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2025 | 1/2 | UCMR-5 |
| Lead | 0.0012 mg/L 8% of the EPA limit 0.0150 mg/L Main supplier: FAIRFAX COUNTY WATER AUTHORITY · 1,121,613 people · 2023 | 2/2 | LCR |
Each bar shows the measured level as a share of the EPA limit: green is
well under, amber is close to it, red is over. For lead and copper the
limit applies to exactly the 90th-percentile figure shown, so red there
means a real exceedance. For everything else the limit applies to a
running annual average while the figure is the 95th percentile of the
system's samples — over 100% is worth reading, but is not by itself a
violation.
Formal violations are listed separately.
These are the utilities' own EPA-reported results, not a city-wide
average. A detection means the lab measured the
substance — it isn't the same as exceeding a legal limit. Hover a source
tag to see the EPA program and years behind each figure.
Water suppliers serving Herndon
| Supplier | Population served |
|---|---|
| FAIRFAX COUNTY WATER AUTHORITY | 1,121,613 |
| HERNDON, TOWN OF | 24,601 |
Frequently asked questions about Herndon tap water
Is Herndon tap water safe to drink?
EPA testing detected 32 contaminants in the water serving Herndon. A detection isn't the same as a violation — most detected levels are within federal limits. Check the level and source for each contaminant above, and your utility's annual Consumer Confidence Report for the official compliance status.
How many water suppliers serve Herndon?
2 public water suppliers report drinking-water monitoring for Herndon, Virginia to the EPA. Each is listed above with its population served.
What contaminants are in Herndon's water?
The contaminants EPA monitoring detected in Herndon include Nitrate-Nitrite, Nitrate, Fluoride, Copper, TTHM. The full list, with the level at the main supplier and the data source, is in the table above.
Where does this data come from?
Every figure is official EPA drinking-water monitoring — the Lead & Copper Rule, the UCMR-5 nationwide testing program, and the EPA Six-Year Review — not our own testing. Each number is labelled with its source and period.