What's in Loudoun County, VA tap water?
Loudoun County sits about 31 miles from our Arlington base and is served primarily by Loudoun Water - Central System, which provides water to roughly 335,000 people. It draws from the Potomac River watershed. Most of the DC metro area drinks treated Potomac River water. Because that surface water is heavily disinfected to stay safe across a long distribution system, the contaminants that most often exceed EWG's stricter health guidelines here are chlorination byproducts, alongside unregulated contaminants like PFAS and hexavalent chromium.
Find a local installerLoudoun Water quality report, explained
What testing of Loudoun Water shows for Loudoun County, compared with EWG's health guidelines. Being above a guideline is not a legal violation.
Primary water system (EPA)
Loudoun Water - Central System
Serves about 335,000 people
Contaminants EWG most often flags above its health guidelines for the Potomac River watershed:
Larger areas have more than one water system. Enter your exact zip code below for your utility's own EPA record and EWG report.
Measured by the EPA · Loudoun County, VA
Loudoun County, VA tap water is fully legal.
It is also 5.5× the health standard for lead.
Loudoun Water - Central System runs Loudoun County's water, drawing from surface water and supplying about 334,808 people through 83,426 service connections. A system that size runs a long distribution network, and water spends days in it between the plant and the tap.
River water has to be disinfected hard enough to stay safe across the whole network, and this system uses chloramines rather than free chlorine. Chloramine is more stable in long pipe runs and produces fewer trihalomethanes — but it is more corrosive to old plumbing, which is precisely how lead gets into water that left the plant clean.
Every federal limit that applies here is met. Those limits weigh what removal costs. EWG says its health standards are “based only on protecting health and does not consider technical feasibility or the cost of water treatment”. Here is how far apart the two are.
Harm to the brain and nervous system · EPA limit 10 ppb (action level, lowered from 15 ppb, in force November 2027)
Harm to fetal growth and child development · no federal limit exists
The EPA's latest round found 1 PFAS compound in this supply. Lead sampling put the ninetieth percentile at 1.1 ppb — meaning nine in ten homes tested below that, and one in ten above it.
Loudoun Water - Central System, on the EPA's record
- Source
- surface water
- Connections served
- 83,426
- People served
- 334,808
- Violations on file
- 2, none health-based
How this water is treated before it reaches you
Treatment makes water safe to distribute. It is not designed to remove PFAS, and chlorine-based disinfection creates byproducts of its own.
Levels: EPA Fifth Unregulated Contaminant Monitoring Rule (UCMR5, 2023–2025) for PFAS, and the Lead and Copper Rule 90th-percentile result for lead and copper — the highest reported for Loudoun Water - Central System. Health standards: EWG's published drinking water standards, updated February 2025. Levels vary by sampling point and date, and being above a health standard is not a legal violation.
13 contaminants above EWG's health guidelines
Everything EWG found above its guideline in Loudoun County's water, from testing in 2013-2024. A level can be under the legal limit and still be listed here: EWG's guidelines are set to protect health, not to be easy to meet.
| Contaminant | In this water | EWG guideline | Times over |
|---|---|---|---|
| Haloacetic acids (HAA9) | 15.3 ppb | 0.06 ppb | 255× |
| Total trihalomethanes (TTHMs) | 28.5 ppb | 0.15 ppb | 190× |
| Haloacetic acids (HAA5) | 14.2 ppb | 0.1 ppb | 142× |
| Bromodichloromethane | 6.80 ppb | 0.06 ppb | 113× |
| Trichloroacetic acid | 5.67 ppb | 0.1 ppb | 57× |
| Chloroform | 18.2 ppb | 0.4 ppb | 45× |
| Dichloroacetic acid | 7.75 ppb | 0.2 ppb | 39× |
| Dibromochloromethane | 3.30 ppb | 0.1 ppb | 33× |
| Dibromoacetic acid | 0.495 ppb | 0.03 ppb | 17× |
| Nitrate and nitrite | 1.36 ppm | 0.14 ppm | 9.7× |
| Chromium (hexavalent) | 0.116 ppb | 0.02 ppb | 5.8× |
| Radium, combined (-226 and -228) | 0.23 pCi/L | 0.05 pCi/L | 4.6× |
| Bromate | 0.351 ppb | 0.1 ppb | 3.5× |
Source: EWG Tap Water Database, Loudoun Water - Central System (VA6107350).
The fix for Loudoun County water
$999$1,250Save $251
or 4 interest-free payments of $249.75 with Shop Pay
Reverse osmosis under your sink, for the contaminants EWG most often flags in the Potomac River watershed.
Free shipping · 60-day returns · 3-year warranty
What’s really in your tap? Find out in seconds.
Common in U.S. tap water
Loudoun County water quality FAQ
Is Loudoun County, VA tap water safe to drink?
Public water in Loudoun County meets federal EPA legal limits. But "legal" is not the same as "clean": across the Potomac River watershed, independent testing routinely finds contaminants like total trihalomethanes (TTHMs) and haloacetic acids (HAA5) above EWG's stricter health guidelines. Enter your zip code above to see your exact utility's record.
What contaminants are common in Loudoun County water?
For the Potomac River watershed, the contaminants that most often exceed health guidelines are total trihalomethanes (TTHMs), haloacetic acids (HAA5), hexavalent chromium (chromium-6), PFAS (forever chemicals) and lead (from older service lines). Your specific levels depend on your utility, which you can look up by zip code above.
Does Sanavia install reverse osmosis systems in Loudoun County?
Yes. Loudoun County is roughly 31 miles from our Arlington base and inside our service area. A Sanavia Hydra reverse osmosis system installs under your sink and reduces every contaminant class above, and we offer a free in-home water test.
Where does Loudoun County tap water come from?
Loudoun County's primary public water system is Loudoun Water - Central System, which serves roughly 335,000 people. It sits in the Potomac River watershed, so its water shares that region's contaminant profile. Larger areas may have more than one utility, so enter your exact zip code above for your own system's EPA record.
Is well water in Loudoun County tested for these contaminants?
No. Private wells are not covered by municipal testing, so the responsibility falls on the homeowner. If your Loudoun County home is on a well, nitrate and naturally occurring contaminants are worth testing for specifically, and a reverse osmosis system reduces them at the tap. We offer a free in-home water test either way.
Contaminants common in the Potomac River watershed
Each of these is a plain-English guide to a contaminant class common in Loudoun County and the surrounding Potomac River watershed — what it is, the health context, and what actually removes it.
Reverse osmosis in Ashburn & Loudoun County, VA
Loudoun Water - Central System treats this water to the federal standard, yet the contaminants listed above still exceed EWG’s stricter health guidelines — Total trihalomethanes (TTHMs), Haloacetic acids (HAA5), Hexavalent chromium (chromium-6) and 2 more. Most of them either pass straight through treatment or form after the plant, in the pipes between it and the tap, which is why the fix has to be at the tap as well.
Lead is the one nothing upstream can fix. It does not arrive from the treatment plant; it comes off the service line and the household plumbing in between, which is why two houses on the same street test differently. A reverse osmosis membrane sits at the end of that run, after every pipe the water has already passed through.
Fit it yourself
$999, under the sink, with the included instructions.
We fit it for you
$1,250 installed in Loudoun County.
Full testing record for Loudoun County · Find a local installer
Detailed city water reports
For the largest DC-metro utilities we publish the full measured contaminant table.
Nearby areas we serve
What's in your Loudoun County tap?
Your water test kit is free.