Seattle, Washington Water Quality Report
Population: 749,256 | Last Updated: 1/14/2024
Overall Water Quality Grade
Based on compliance rates, contaminant levels, and treatment effectiveness
Water Sources
Seattle receives its drinking water from multiple sources:
Cedar River Watershed
70%Surface Water
Protected watershed in the Cascade Mountains, naturally filtered through ancient forest
Tolt River Watershed
30%Surface Water
Supplementary source from protected watershed in the Cascade foothills
Detected Contaminants
All contaminants listed below are within legal limits, but some may exceed health guidelines.
| Contaminant | Detected Level | Legal Limit | Health Goal | Status | Trend |
|---|---|---|---|---|---|
| Lead | 2.1 ppb | 15 ppb | 0 ppb | Below Legal Limit | ↓ improving |
| Total Trihalomethanes (TTHMs) | 28 ppb | 80 ppb | 0 ppb | Below Legal Limit | → stable |
| Haloacetic Acids (HAA5) | 18 ppb | 60 ppb | 0 ppb | Below Legal Limit | → stable |
| Chlorine | 0.7 ppm | 4 ppm | 4 ppm | Optimal | → stable |
Comparison with Washington State Average
Lead Compliance
4.0 points above state average
Bacterial Compliance
2.0 points above state average
Chemical Compliance
3.0 points above state average
Overall Score
7.0 points above state average
Water Quality Trends
Overall water quality score over the past 5 years
Water quality has improved by 2.0 points since 2019
Contamination History
Tolt River Turbidity Event
Heavy rainfall caused temporary elevated turbidity in Tolt River source
Resolution:
Additional treatment processes activated, water quality quickly restored, no health impacts
Frequently Asked Questions - Seattle Water Quality
Is Seattle tap water safe to drink?
Yes, Seattle has some of the best tap water in the nation. The water comes from protected mountain watersheds and undergoes advanced treatment. Seattle's water consistently meets or exceeds all federal and state standards and has won national taste awards.
Why is Seattle water so good?
Seattle's water quality benefits from pristine mountain watershed sources in protected old-growth forests of the Cascades. The naturally soft water requires minimal treatment, and Seattle uses advanced UV disinfection and ozonation rather than heavy chlorination.
Is Seattle water soft or hard?
Seattle has very soft water (22 mg/L hardness), among the softest of any major US city. This means less mineral buildup on fixtures and appliances, better soap lathering, and a naturally pleasant taste.
Does Seattle add fluoride to the water?
No, Seattle does not fluoridate its water supply. Voters have rejected fluoridation multiple times, most recently in 2011. The city provides information about alternative sources of fluoride for dental health.
How does Seattle protect its water sources?
Seattle owns and manages over 100,000 acres of protected watershed land in the Cascade Mountains. Public access is prohibited to prevent contamination, and the watersheds are managed for water quality protection and forest health.
Nearby Water Utilities
Compare water quality in nearby cities:
Bellevue, WA
Tacoma, WA
Everett, WA
Renton, WA
Utility Information
Water Provider
Seattle Public Utilities
Contact Information
Customer Service: 206-684-3000
Emergency: 206-386-1800
Data Disclaimer
This water quality report is compiled from publicly available data and annual water quality reports. For the most current information, please contact your local water utility or visit their official website. Last updated: 1/14/2024.