What was found in Seattle'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 | 1054 µg/L 11% of the EPA limit 10000 µg/L Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2019
Highest in the city: 2780 µg/L — SKYWAY WATER & SEWER · 12,036 people · 2019 | 2/5 | SYR4 |
| Nitrate-Nitrite | 880 µg/L 8.8% of the EPA limit 10000 µg/L Highest in the city: SKYWAY WATER & SEWER · 12,036 people · 2019 | 1/5 | SYR4 |
| Fluoride | 795 µg/L 20% of the EPA limit 4000 µg/L Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2012 | 2/5 | SYR4 |
| Total Haloacetic Acids (HAA5) | 50.606 µg/L 84% of the EPA limit 60 µg/L Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2019
Highest in the city: 59.865 µg/L — SKYWAY WATER & SEWER · 12,036 people · 2019 | 4/5 | SYR4 |
| TTHM | 49.723 µg/L 62% of the EPA limit 80 µg/L Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2019 | 4/5 | SYR4 |
| Chloroform | 45.3 µg/L No EPA limit set Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2019
Highest in the city: 46.26 µg/L — KING COUNTY WATER DISTRICT #20 · 48,469 people · 2019 | 4/5 | SYR4 |
| Trichloroacetic Acid | 29.75 µg/L No EPA limit set Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2019
Highest in the city: 34 µg/L — SKYWAY WATER & SEWER · 12,036 people · 2019 | 4/5 | SYR4 |
| Dichloroacetic Acid | 23.5 µg/L No EPA limit set Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2019
Highest in the city: 26.38 µg/L — SKYWAY WATER & SEWER · 12,036 people · 2019 | 4/5 | SYR4 |
| Arsenic | 8.08 µg/L 81% of the EPA limit 10 µg/L Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2012 | 1/5 | SYR4 |
| Barium | 3.48 µg/L 0.2% of the EPA limit 2000 µg/L Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2012
Highest in the city: 7 µg/L — SKYWAY WATER & SEWER · 12,036 people · 2019 | 2/5 | SYR4 |
| Bromodichloromethane | 2.7465 µg/L No EPA limit set Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2019
Highest in the city: 6.799 µg/L — SKYWAY WATER & SEWER · 12,036 people · 2019 | 4/5 | SYR4 |
| Monochloroacetic Acid | 3.515 µg/L No EPA limit set Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2019
Highest in the city: 4.725 µg/L — SKYWAY WATER & SEWER · 12,036 people · 2019 | 4/5 | SYR4 |
| Copper | 4.35 µg/L 0.3% of the EPA limit 1300 µg/L Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2012 | 1/5 | SYR4 |
| Dibromochloromethane | 1.922 µg/L No EPA limit set Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2019
Highest in the city: 3.6985 µg/L — SKYWAY WATER & SEWER · 12,036 people · 2019 | 4/5 | SYR4 |
| Gross Beta Particle Activity | 2.36 pCi/L No EPA limit set Highest in the city: SKYWAY WATER & SEWER · 12,036 people · 2018 | 1/5 | SYR4 |
| Nitrite | 2 µg/L 0.2% of the EPA limit 1000 µg/L Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2019 | 1/5 | SYR4 |
| Chromium | 1.2 µg/L 1.2% of the EPA limit 100 µg/L Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2012 | 1/5 | SYR4 |
| Selenium | 1.2 µg/L 2.4% of the EPA limit 50 µg/L Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2012 | 1/5 | SYR4 |
| Dibromoacetic Acid | 0.7886 µg/L No EPA limit set Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2019
Highest in the city: 0.8365 µg/L — SKYWAY WATER & SEWER · 12,036 people · 2019 | 3/5 | SYR4 |
| Bromoform | 0.6500 µg/L No EPA limit set Highest in the city: KING COUNTY WATER DISTRICT #20 · 48,469 people · 2019 | 1/5 | SYR4 |
| Lead | 0.0016 mg/L 11% of the EPA limit 0.0150 mg/L Main supplier: SEATTLE PUBLIC UTILITIES · 1,161,961 people · 2025
Highest in the city: 0.0020 mg/L — HOT SPRINGS COURT · 55 people · 2025 | 3/5 | 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 Seattle
| Supplier | Population served |
|---|---|
| SEATTLE PUBLIC UTILITIES | 1,161,961 |
| KING COUNTY WATER DISTRICT #20 | 48,469 |
| KING COUNTY WATER DISTRICT #125 | 21,904 |
| SKYWAY WATER & SEWER | 12,036 |
| HOT SPRINGS COURT | 55 |
Frequently asked questions about Seattle tap water
Is Seattle tap water safe to drink?
EPA testing detected 21 contaminants in the water serving Seattle. 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 Seattle?
5 public water suppliers report drinking-water monitoring for Seattle, Washington to the EPA. Each is listed above with its population served.
What contaminants are in Seattle's water?
The contaminants EPA monitoring detected in Seattle include Nitrate, Nitrate-Nitrite, Fluoride, Total Haloacetic Acids (HAA5), 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.