What's in Washington, DC tap water?
Washington, DC tap water is treated by DC Water using the Washington Aqueduct's Potomac River source. It meets federal legal limits, but EWG testing flags several disinfection byproducts and other contaminants well above health-based guidelines.
DC Water quality report, explained
What DC Water's own test results show for Washington, compared with EWG's health guidelines. Every result here is within EPA legal limits.
Surrounding area addresses
DC Water
Washington Aqueduct, Potomac River
Washington itself is on its own treatment plant — see above. Addresses just outside the city line are on DC Water.
13
over guideline
Zip codes covered: 20001, 20002, 20009, 20011, 20016, 20024, 20037 and surrounding Washingtonareas. “× over” compares the detected level to EWG's health guideline, not the federal legal limit.
Measured by the EPA · Washington, DC
Washington, DC runs its own water system — and it has not been tested for PFAS.
Washington is served by Washington Aqueduct Division, a surface-water system supplying roughly 0 people. It treats its own water rather than buying it from a regional wholesaler, so what comes out of the tap is its work end to end.
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.
Washington Aqueduct Division was not part of the EPA's most recent national PFAS monitoring round, so there is no federal PFAS result for it. Nobody has looked, which is not the same as nothing being there. No lead or copper results appear in EPA's published record for this system.
Washington Aqueduct Division, on the EPA's record
- Source
- surface water
- Connections served
- 3
- Violations on file
- 1, 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.
Source: EPA Safe Drinking Water Information System record for Washington Aqueduct Division (PWSID DC0000001). Systems outside the UCMR5 sample are not required to test for PFAS.
13 contaminants above EWG's health guidelines
Everything EWG found above its guideline in Washington's water, from testing in 2014-2024. 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) | 42.4 ppb | 0.06 ppb | 707× |
| Haloacetic acids (HAA5) | 31.4 ppb | 0.1 ppb | 314× |
| Total trihalomethanes (TTHMs) | 46.4 ppb | 0.15 ppb | 310× |
| Bromodichloromethane | 11.9 ppb | 0.06 ppb | 198× |
| Bromochloroacetic acid | 3.57 ppb | 0.02 ppb | 179× |
| Trichloroacetic acid | 14.7 ppb | 0.1 ppb | 147× |
| Chloroform | 31.4 ppb | 0.4 ppb | 79× |
| Dichloroacetic acid | 14.9 ppb | 0.2 ppb | 75× |
| Dibromochloromethane | 3.08 ppb | 0.1 ppb | 31× |
| Arsenic | 0.109 ppb | 0.004 ppb | 27× |
| Nitrate | 1.97 ppm | 0.14 ppm | 14× |
| Radium, combined (-226 and -228) | 0.38 pCi/L | 0.05 pCi/L | 7.6× |
| Chromium (hexavalent) | 0.0863 ppb | 0.02 ppb | 4.3× |
Source: EWG Tap Water Database, DC Water (DC0000002).
The fix for Washington water
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Washington water quality FAQ
Is Washington, DC tap water safe to drink?
Water from DC Water meets all federal EPA legal limits. However, independent EWG testing finds 13 contaminants above its stricter health-based guidelines, including haloacetic acids (HAA9) and haloacetic acids (HAA5). Legal compliance and health-optimal water are not the same thing.
What contaminants are in Washington water?
The most notable contaminants above EWG health guidelines are haloacetic acids (HAA9), haloacetic acids (HAA5), total trihalomethanes (TTHMs), bromodichloromethane and 9 more. These are largely disinfection byproducts and trace metals common to the region's water sources.
Does a reverse osmosis system remove these contaminants?
Yes. A reverse osmosis system like the Sanavia Hydra uses a 0.0001-micron membrane plus multi-stage carbon filtration to reduce every contaminant class detected in Washington water, at your tap, regardless of what the utility does upstream.
The contaminants flagged in Washington water
Plain-English guides to what DC Watertesting turns up above EWG's health guidelines — what each one is, and what actually removes it.
Reverse osmosis in Washington, DC
DC Water treats this water to the federal standard, yet the contaminants listed above still exceed EWG’s stricter health guidelines — Haloacetic acids (HAA9), Haloacetic acids (HAA5), Total trihalomethanes (TTHMs) and 10 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.
Trihalomethanes and haloacetic acids are not in the river — they form in the pipes, after treatment, when chlorine meets the organic matter it is there to deal with. That is why they are worst at the far end of a distribution network, and why filtering at the tap catches them where testing at the plant cannot.
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