Seattle, Washington Tap Water Quality Report
Serving utility: Seattle Public Utilities
Updated March 2026 • Data from EWG Tap Water Database & EPA SDWIS
High Priority Concerns
Seattle tap water has 11 contaminants exceeding EWG health guidelines, including Haloacetic acids (HAA9), Haloacetic acids (HAA5), Total trihalomethanes (TTHMs). Additionally, 10 known or suspected carcinogens were detected, including Haloacetic acids (HAA9), Haloacetic acids (HAA5), Total trihalomethanes (TTHMs).
Water Provider Information
Contaminants Detected
| Contaminant | Detected Level | EWG Guideline | Legal Limit | Status |
|---|---|---|---|---|
| Haloacetic acids (HAA9) carcinogen | 27.30 ppb | 0.06 ppb | No legal limit | Above guideline |
| Haloacetic acids (HAA5) carcinogen | 28.90 ppb | 0.10 ppb | 60 ppb | Above guideline |
| Total trihalomethanes (TTHMs) carcinogen | 28.70 ppb | 0.15 ppb | 80 ppb | Above guideline |
| Trichloroacetic acid carcinogen | 14.90 ppb | 0.10 ppb | No legal limit | Above guideline |
| Chloroform carcinogen | 27 ppb | 0.40 ppb | No legal limit | Above guideline |
| Dichloroacetic acid carcinogen | 12.70 ppb | 0.20 ppb | No legal limit | Above guideline |
| Bromodichloromethane carcinogen | 1.69 ppb | 0.06 ppb | No legal limit | Above guideline |
| Radium, combined (-226 and -228) | 0.71 pCi/L | 0.05 pCi/L | 5 pCi/L | Above guideline |
| Chromium (hexavalent) carcinogen | 0.12 ppb | 0.02 ppb | No legal limit | Above guideline |
| Bromate carcinogen | 0.35 ppb | 0.10 ppb | 10 ppb | Above guideline |
| Bromochloroacetic acid | 0.07 ppb | 0.02 ppb | No legal limit | Above guideline |
| Chlorate | 16.10 ppb | 210 ppb | No legal limit | Below guideline |
| Manganese | 1.93 ppb | 100 ppb | No legal limit | Below guideline |
| Monochloroacetic acid | 1.26 ppb | 53 ppb | No legal limit | Below guideline |
| Nitrate carcinogen | 0.06 ppm | 0.14 ppm | 10 ppm | Below guideline |
| Strontium | 0.03 ppb | 1,500 ppb | No legal limit | Below guideline |
| Vanadium | 0.48 ppb | 21 ppb | No legal limit | Below guideline |
Health Context
Haloacetic acids (HAA9) carcinogen
Exposure to elevated levels of this contaminant may pose health risks. See EWG and EPA guidelines for more information.
Haloacetic acids (HAA5) carcinogen
Exposure to elevated levels of this contaminant may pose health risks. See EWG and EPA guidelines for more information.
Total trihalomethanes (TTHMs) carcinogen
Exposure to elevated levels of this contaminant may pose health risks. See EWG and EPA guidelines for more information.
Trichloroacetic acid carcinogen
Exposure to elevated levels of this contaminant may pose health risks. See EWG and EPA guidelines for more information.
Chloroform carcinogen
Chloroform is the most abundant trihalomethane (THM) disinfection byproduct and a probable human carcinogen that accumulates in body tissues. Chronic exposure increases colorectal and bladder cancer risk and causes liver/kidney damage.
Recommended Filtration for This Water
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Shop Hydrogen FlaskFrequently Asked Questions
Is Seattle tap water safe to drink?
Seattle tap water meets EPA legal standards for drinking water. However, 11 contaminants exceed stricter EWG health guidelines, and 10 known carcinogens were detected. While legally compliant, additional filtration is recommended for optimal safety.
What contaminants are in Seattle water?
A total of 17 contaminants were detected in Seattle tap water, including Haloacetic acids (HAA9), Haloacetic acids (HAA5). Of these, 11 exceed EWG health guidelines.
What's the best water filter for Seattle?
For Seattle tap water, we recommend a reverse osmosis (RO) system for drinking water — it removes up to 99.9% of contaminants including heavy metals, PFAS, and disinfection byproducts. For shower and bath water, a whole-home filtration system reduces chlorine and volatile organics.
Where does Seattle get its water?
Seattle tap water is provided by Seattle Public Utilities, serving approximately 1,091,904 people. For detailed source water information, contact your local utility or visit the EPA's SDWIS database.
Nearby City Water Reports
Data sources: Environmental Working Group (EWG) Tap Water Database, U.S. EPA Safe Drinking Water Information System (SDWIS)
Last updated: March 2026
Methodology: Contaminant levels are compared against both EPA legal limits (Maximum Contaminant Levels) and EWG health guidelines, which are often stricter and based on the latest scientific research.
