Washington State generally provides its residents with high-quality drinking water, particularly in densely populated municipal areas. This reliability is due to regulatory frameworks and advanced treatment systems that manage large water sources. However, the safety of the water supply is not uniform across the state, varying significantly based on whether a home is connected to a public water system or relies on a private well. Understanding the source of your water is the first step in assessing its quality and identifying potential localized risks.
The Regulatory Framework and Public System Reliability
The vast majority of Washington residents are served by public water systems, which are subject to rigorous oversight. This regulatory structure begins at the federal level with the Environmental Protection Agency (EPA) enforcing the Safe Drinking Water Act (SDWA). The Washington State Department of Health (DOH) has a formal “primacy” agreement with the EPA, allowing the state to administer and enforce these federal standards.
These public water systems must adhere to monitoring, testing, and reporting requirements. The DOH monitors their performance and compliance with state and federal regulations through a mandatory annual operating permit program. Public utilities must test their water for contaminants.
The annual Consumer Confidence Report (CCR) is a key tool for public transparency. Every public water system must provide this report to its customers, detailing the source of the water, the contaminants detected, and compliance with all drinking water standards. Furthermore, in cases of an acute health risk, such as bacterial contamination, the utility must notify its customers within 24 hours.
Groundwater Reliance and Private Well Safety
While most of the population receives water from regulated public sources, a significant number of Washington residents, rely on individual private wells. Private wells are not subject to the continuous testing and regulatory requirements mandated for public systems.
The safety of a private well is the sole responsibility of the homeowner. Neither the DOH nor the EPA regulates the water quality of a private well after its initial installation. This lack of ongoing oversight means that contamination can occur without the homeowner’s knowledge, as many contaminants are odorless and tasteless.
Private well water is especially vulnerable to localized issues, including proximity to septic systems, agricultural runoff, and naturally occurring geological contaminants. The DOH recommends that private well owners test their water annually for coliform bacteria and nitrate. Testing is also advised whenever there is a change in the water’s taste, odor, or appearance, or after events like flooding that could compromise the well seal.
Key Contaminants and Regional Concerns
Specific contaminants pose localized risks across Washington State, often linked to the source water type or the age of the infrastructure. Lead is one such contaminant, though it rarely originates in the state’s source water. The primary risk comes from older homes and buildings where water interacts with lead service lines, lead-containing solder in plumbing, or brass fixtures.
Naturally occurring elements like arsenic and radon concern groundwater users on private wells. Elevated arsenic levels are found in certain geological regions, including parts of the Puget Sound basin, such as areas of King and Snohomish counties, and on South Whidbey Island. Arsenic concentrations in well water can also fluctuate seasonally, making consistent testing necessary for an accurate assessment.
Radon is a radioactive gas that can enter well water from the decay of uranium in underlying rock and soil. It can be found in groundwater, especially in areas like Spokane and Clark counties, and in a patchwork of regions across the Cascades and Eastside.
An emerging concern statewide is Per- and polyfluoroalkyl substances (PFAS), a group of man-made chemicals often linked to industrial sites or the historical use of firefighting foam. The DOH has established state action levels for specific PFAS compounds, requiring public systems to monitor for them.
How to Check Your Local Water Quality
Verifying the safety of your water source requires accessing specific data relevant to your location. If you receive water from a public system, you should look for your utility’s Consumer Confidence Report (CCR). This report is often available on the water utility’s website.
For a more detailed look at a public system’s history and compliance, the DOH maintains the Sentry Internet Database, which contains summary information on compliance actions and water quality data. This database allows residents to search for specific data on their water provider.
Private well owners must take a proactive approach, beginning with professional testing for bacteria, nitrate, and arsenic. The DOH recommends testing for coliform bacteria and nitrate annually. Finding an accredited laboratory to perform the analysis is crucial, and certified labs can be located through the Department of Ecology or your local health department.