Tap Water Quality Report
Tap water quality in Seattle, Washington
Tap water in Seattle, Washington receives a grade of C (78/100) from TapWaterSafety.org. It's served by SEATTLE PUBLIC UTILITIES. The most significant water quality concerns are: Haloacetic acids (HAA9) significantly above health guideline; Haloacetic acids (HAA5) significantly above health guideline; Total trihalomethanes (TTHMs) significantly above health guideline. Data sources: EPA SDWIS, EPA ECHO, EWG Tap Water Database.
What's in Seattle's tap water
Top water quality concerns identified by the EPA and Environmental Working Group across the utility serving Seattle.
Haloacetic acids (HAA9) significantly above health guideline
Moderate concernHaloacetic acids (HAA9) detected at 27.3 ppb, 455x above the EWG health guideline of 0.06 ppb.
Haloacetic acids (HAA5) significantly above health guideline
Moderate concernHaloacetic acids (HAA5) detected at 28.9 ppb, 289x above the EWG health guideline of 0.1 ppb.
Total trihalomethanes (TTHMs) significantly above health guideline
Moderate concernTotal trihalomethanes (TTHMs) detected at 28.7 ppb, 192x above the EWG health guideline of 0.15 ppb.
EPA compliance record
Official U.S. EPA records for SEATTLE PUBLIC UTILITIES (system ID WA5377050) for the last 3 years. Checked 2026-10-07.
Source: U.S. EPA Enforcement and Compliance History Online (ECHO), from the Safe Drinking Water Information System. See EPA's full report.
Recommended filters for Seattle
Filters matched to the specific contaminants in Seattle's water supply.
Carbon filter certified for VOCs (NSF/ANSI 53)
$180-$599Activated carbon is effective for disinfection byproducts. Look for NSF/ANSI 53 VOC reduction.
Disclosure: TapWaterSafety earns a commission from purchases made through these links. This does not influence our scoring methodology or filter selection.
All contaminants detected in Seattle's tap water
Every contaminant identified, compared side-by-side against US EPA legal limits, the EU Drinking Water Directive (2020/2184), WHO Guidelines, and California's Public Health Goal. Why we show multiple standards →
| Contaminant | Detected | EWG US health-based |
EPA US legal |
EU DWD Europe |
WHO global |
CA PHG strictest US |
Tested sample year |
Status |
|---|---|---|---|---|---|---|---|---|
| Haloacetic acids (HAA9) Disinfection byproduct |
27.3 ppb | 0.06 | — | — | — | — | — | 455× over |
| Haloacetic acids (HAA5) Disinfection byproduct |
28.9 ppb | 0.1 | 60.0 | 60 | — | — | — | 289× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
28.7 ppb | 0.15 | 80.0 | 100 | — | — | — | 192× over |
| Trichloroacetic acid Disinfection byproduct |
14.9 ppb | 0.1 | — | — | — | — | — | 149× over |
| Chloroform Disinfection byproduct |
27.0 ppb | 0.4 | — | — | — | — | — | 68× over |
| Dichloroacetic acid Disinfection byproduct |
12.7 ppb | 0.2 | — | — | — | — | — | 64× over |
| Bromodichloromethane Disinfection byproduct |
1.69 ppb | 0.06 | — | — | — | — | — | 28× over |
| Radium, combined (-226 and -228) Radiological |
0.71 pCi/L | 0.05 | 5.0 | — | — | — | — | 14× over |
| Chromium (hexavalent) Heavy metal |
0.116 ppb | 0.02 | — | — | — | — | — | 5.8× over |
| Bromate Disinfection byproduct |
0.352 ppb | 0.1 | 10.0 | 10 | 10 | 0.1 | — | 3.5× over |
| Bromochloroacetic acid Disinfection byproduct |
0.0664 ppb | 0.02 | — | — | — | — | — | 3.3× over |
| Nitrate Inorganic |
0.062 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | Below guideline |
| Chlorate Disinfection byproduct |
16.1 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Monochloroacetic acid Disinfection byproduct |
1.26 ppb | 53.0 | — | — | — | — | — | Below guideline |
| Vanadium Other |
0.483 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Manganese Heavy metal |
1.93 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Strontium Radiological |
0.0291 ppb | 1500.0 | — | — | — | — | — | Below guideline |
All values in the unit of the detected level. Red cells indicate the detected level exceeds that standard. Some contaminants have limits in some jurisdictions but not others (shown as —). The "Tested" column shows the year each contaminant sample was collected.
Sources: US EPA, EU Drinking Water Directive 2020/2184, WHO Guidelines, California OEHHA PHGs, EWG Tap Water Database.
Treatment plant contact info
For service issues, water quality concerns, or to request a Consumer Confidence Report from SEATTLE PUBLIC UTILITIES.
General Contact
Treatment Plant
ZIP codes served
Seattle's public water systems serve the following ZIP codes: