Is Herndon, VA Tap Water Safe to Drink?
Yes, Herndon tap water is safe to drink. Hardness is low at 110 PPM, and no contaminants exceed health guidelines. Most homes here don't need treatment.
Hardness Scale: Where Herndon Falls
0Slightly
60Moderate
120Hard
180Very Hard
250Extreme
400+
How Herndon Compares
Herndon's water is close to the national average of 138 PPM, ranking #551 out of 1000 cities tracked. Within Virginia, Herndon has the 2nd hardest water out of 22 cities - 116% above the state average of 51 PPM. Among smaller cities, Herndon ranks #132 of 288 for hardness.
What Herndon's Water Means for Your Home
Hardness: 110 PPM - Low Concern
Herndon's water is firmly in the moderate range at 110 PPM. You'll see some spotting on glassware and a film on shower doors over time, but it's not the kind of hardness that demands a full softener. A salt-free conditioner is worth considering if you have a tankless water heater or high-end fixtures.
Contaminants & Safety
Disinfection byproducts are the notable finding here. Herndon's water has TTHMs at 19.7 ppb and HAA5 at 12.8 ppb — both within legal limits, but the EWG health guidelines are far stricter. These byproducts form when chlorine reacts with organic matter during treatment. A whole-house activated carbon filter reduces both chlorine and its byproducts. Want the full picture? Request your utility's annual Consumer Confidence Report.
What's in the Treatment Process
Herndon's surface water supply requires heavy chlorination to stay safe — but that creates a tradeoff. The treatment process generates disinfection byproducts: TTHMs at 19.7 ppb (25% of the legal limit, but 131x the EWG guideline) and HAA5 at 12.8 ppb (21% of the legal limit, but 128x the EWG guideline). These are within legal limits, but the EWG sets much tighter thresholds based on cancer-risk research. A whole-house activated carbon filter reduces both chlorine and byproducts.
Chromium-6 was detected at 0.169 ppb, which is 8.4x the EWG health guideline. There's no separate federal limit for chromium-6, only total chromium. A reverse osmosis system is the most effective removal method. All measurements are within federal legal limits. The EWG guidelines represent a more conservative, health-based standard.
| Contaminant | Detected | Health Guideline | Legal Limit | Status |
|---|---|---|---|---|
| Hardness (as CaCO₃) | 110 PPM | < 60 PPM | No federal limit | ✓ OK |
| Total Dissolved Solids | 185 PPM | < 300 PPM | 500 PPM | ✓ OK |
| PFAS (total) | 12.5 ppt | — | No total limit | Detected |
| ↳ PFOA | 0 ppt | 0 ppt | 4 ppt (2024) | ✓ OK |
| ↳ PFOS | 0 ppt | 0 ppt | 4 ppt (2024) | ✓ OK |
| Lead | 0.4 ppb | 0 ppb (no safe level) | 15 ppb (10 ppb in 2027) | ✓ Low |
| Chlorine / Chloramine | 1.4 mg/L | Taste threshold ~1.0 | 4.0 mg/L | ✓ Normal |
| Nitrate | 1.12 mg/L | 5 mg/L | 10 mg/L | ✓ OK |
Recommendations for Herndon Homes
Quick Fix for Chlorine: Shower Filter
At 1.4 mg/L chlorine, many Herndon residents notice dry skin, brittle hair, and that "pool smell" in the shower. A shower filter installs in 5 minutes, no tools needed.
How to Test Your Water in Herndon
City-wide data is a solid starting point, but your specific tap might differ based on plumbing age, distance from the treatment plant, or seasonal changes.
Free option: Request Fairfax Water's annual Consumer Confidence Report for official city-level data.
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About Herndon's Water Supply
Water Utility: Fairfax Water
Water Source: Potomac River (Fairfax Water) (Surface Water)
Population Served: 24,601
Hardness: 110 PPM (6.4 grains per gallon)
Herndon's drinking water comes from surface sources — Potomac River (Fairfax Water). Surface water requires more extensive treatment than groundwater, including coagulation, filtration, and disinfection. This heavier chlorination is why disinfection byproducts tend to be higher in surface-supplied systems. On the upside, surface sources often deliver softer water than deep aquifers. The system serves 25,000 residents.
Water quality can vary by neighborhood and season. For your exact numbers, request Fairfax Water's Consumer Confidence Report (CCR) or test your own tap.
ZIP Codes Covered by This Report
This water quality data applies to all areas served by Fairfax Water in Herndon, VA, including ZIP codes:
20101, 20102, 20103, 20104, 20105, 20117, 20118, 20122, 20131, 20132, 20135, 20141, 20142, 20146, 20147, 20148, 20149, 20151, 20152, 20153, 20160, 20163, 20164, 20166, 20167, 20170, 20171, 20172, 20175, 20185, 20189, 20190, 20191, 20192, 20194, 20195, 20196, 20598, 22009, 22015, 22030, 22031, 22032, 22033, 22034, 22035, 22037, 22038, 22066, 22067, 22095, 22096, 22103, 22118, 22119, 22124, 22156, 22158, 22159, 22160, 22180, 22181, 22182, 22183, 22185, 22611, 22620, 22646, 22655, 22663
If your ZIP code is listed above, this report covers your water supply. Water quality may vary slightly by neighborhood.
Compare Herndon to Other Virginia Cities
Frequently Asked Questions About Herndon Water
Is Herndon tap water safe to drink?
Where does Herndon's water come from?
Do I need a water softener in Herndon?
What is the hardness of Herndon water in grains per gallon?
What are disinfection byproducts in Herndon's water?
Is chromium-6 in Herndon's water?
Why does Herndon water taste like chlorine?
Can I drink Herndon tap water straight from the faucet?
Data sources: Lead and copper data from EPA Safe Drinking Water Act LCR reporting. Contaminant data from utility-reported testing results. PFAS data from EPA UCMR5 (2023–2025). Hardness from USGS and municipal reports. Data reflects system-level testing results and may not match your specific tap due to neighborhood plumbing, season, or recent utility changes. For your utility's latest results, request their Consumer Confidence Report (CCR). Our methodology. Last updated: 2026-02-24.
What Herndon Homeowners Actually Buy
Common purchases for homes with 110 PPM water.
Affiliate disclosure: we may earn a commission. Selection based on Herndon's water data.