Understanding Lead in King County Water: Interpreting Local Water Sampling Data

The public water system serving King County recorded a 90th percentile lead level of 0.0033 mg/L in routine sampling dated December 31, 2025. This figure refers to distribution system measurements across homes served by the Lakehaven Water and Sewer District, not to any individual household's water.

1. Reading Median and Range Data in the Lead Sampling Record

The 90th percentile value means 90% of tested homes had lead concentrations at or below 0.0033 mg/L. This is a statistical measure rather than a direct reading from your home. It reflects lead measurements influenced by plumbing materials, water chemistry, and sampling methods within the served area, not the source water itself.

Because lead levels can vary widely between homes depending on plumbing and fixtures, this central figure helps understand the typical upper range of exposure across many residences. However, it does not indicate a legal violation or unsafe condition, as no health-based violations are recorded for this system.

2. Fixtures, Appliances, or Processes Likely to Show Lead First

Lead contamination in household water generally originates from plumbing components rather than the water source. Faucets, especially older brass fixtures, lead service lines, and internal solder can contribute lead where water sits stagnant for several hours.

Fixtures used sporadically or those with infrequent flushing tend to show higher lead concentrations first. Appliances connected to cold water lines such as ice makers or refrigerators may also accumulate lead if water remains stagnant in small-diameter tubing.

3. Household Size and Usage Patterns That Affect Lead Levels

Larger households with higher water turnover may reduce lead levels by preventing stagnation. Conversely, a second home or seasonal property with infrequent water use might experience higher lead concentrations as water remains in contact with metal plumbing components longer.

Understanding your household’s water use patterns is critical to anticipating potential lead exposure. Homes with extended periods of inactivity should consider flushing taps before use or testing individual water samples for accurate assessment.

4. Sample Size and Scope Behind the Lead Figures

The published lead level is based on sampling multiple homes across the public water supply territory, encompassing almost 47,000 connections. This large sample size offers a reliable regional overview but cannot substitute for individual water testing at a specific residence.

Sampling programs aim to capture a broad cross-section to identify trends and compliance with regulatory expectations. Smaller sample sets can introduce variability and limit confidence about any single home’s water quality.

5. Steps to Identify the Cause and Address Lead Concerns

• Start with flushing taps that have been unused overnight or during prolonged absence to reduce stagnation effects.
• Inspect visible plumbing for materials known to contain lead, if accessible.
• Obtain a certified laboratory test of your household water to confirm lead levels specific to your plumbing.
• If testing shows elevated lead, consider treatment options designed for lead reduction, such as the Fleck Lead in Water Filter, which ships ready to configure for residential use.

This briefing has walked through how to interpret local lead data, identify potential household exposure points, and outline steps to clarify your specific water quality. The next phase is to test your own water and then decide if targeted treatment is the right course.

Where this information comes from

Source: EPA SDWIS public water system record. Sampled 2025-12-31. These figures describe the public water system's record, not the plumbing inside any individual building.

On record: EPA SDWIS record for LAKEHAVEN WATER AND SEWER DISTRICT (WA5341997), surface water supply, serving 148809 people: 0 health-based violations of 1 total; lead 90th percentile 0.0033 mg/L