Water Quality Lab Testing

The mission of the Seattle Public Utility (SPU) Water Quality Laboratory is to provide water laboratory services including sample collection, analysis, data management, reporting, and consultations that sustain regulatory compliance, facilitate operational decisions, and help protect customer health. Analysts conduct microbial, chemical and physical monitoring daily, 365 days per year, testing over 20,000 samples each year.

This facility is the largest state-accredited water utility laboratory. Tests are conducted on water from all parts of the Seattle system as well as for other water utilities in the region.

Chemistry, Limnology, & Microbiology

Chemistry staff members provide sample processing for fluoride, turbidity, pH, alkalinity, conductivity, UV absorbance, chlorine demand, and screening for synthetic and volatile organics. Some of these analyses are also conducted at the water treatment facilities.

The SPU laboratory conducts tests for inorganic chemicals (including lead, copper, cadmium, arsenic, barium, chromium, selenium, silver, nitrate and nitrite) and organic chemicals (such as haloacetic acids and trihalomethanes).

Limnology staff members monitor and sample Seattle’s two drinking water sources: the South Fork Tolt River and Cedar River source waters, the Lake Youngs reservoir, and the storage reservoirs within the City of Seattle. Analyses of biological samples, algae identification, algal toxins, and taste and odor flavor profile analyses are also conducted.

Microbiology staff members provide testing of water samples collected from both the Cedar and Tolt River watersheds, and from sites throughout the retail and wholesale distribution systems. Samples are tested for coliform bacteria, E. coli, and heterotrophic bacteria. Additionally, water temperature and chlorine residual tests are done in the field at each sample collection site.

Seattle Public Utilities (SPU) provides some of the highest quality drinking water in the nation because it comes from pristine, protected mountain sources: the Cedar River Watershed and South Fork Tolt River Watershed. To ensure the safety of our drinking water, SPU's water quality laboratory analyzes over 20,000 microbiological samples each year (more than 50 a day) and conducts chemical and physical monitoring daily, 365 days per year.

Each year, SPU publishes a Drinking Water Quality Report that summarizes water quality information for the year as required under the federal Safe Drinking Water Act. More detailed information can be found on the Water Quality Analyses page, which includes quarterly reports and annual summaries for dozens of drinking water quality parameters.