King County Water District #20
EPA ID: WA5338950 · 38,974 people served · 62 ZIP codes
ZipCheckup's reading of EPA SDWIS for King County Water District #20 (WA5338950): 1 EPA violation in the last five years. While 1 violation did appear in King County Water District #20's five-year monitoring record, none remain unresolved - the utility has returned to full compliance and continues to serve approximately 38,974 residents under all current EPA drinking water standards.
Data: EPA SDWIS Last verified: 2026-04-02
Service Area Map
Coverage area for King County Water District #20 Source: EPA SDWIS service area boundaries.
Service area boundary - Grade A
Service Area Demographics
The King County Water District #20 serves a community with a median household income of $114,213 and an estimated 994,393 residents across its service area. Approximately 63% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
🌊 Where Does Your Water Come From?
King County Water District #20's water is drawn from rivers, lakes, or reservoirs. Surface water sources are more exposed to agricultural runoff, stormwater, and upstream discharges, but they typically receive more intensive treatment before reaching your tap.
Superfund Proximity Note: This service area ranks in the 69th percentile nationally for proximity to Superfund (NPL) sites.
Infrastructure Risk
Detected Contaminants
How King County Water District #20 compares to EPA limits
What This Means For You
Surface Water Treatment Rule at 1 mg/L exceeds the EPA maximum of mg/L.
PFAS Detected in Service Area
PFAS ("forever chemicals") have been detected in water serving this system's area. 2 detections recorded.
Comparable Water Systems
Similar-sized systems in Washington
Estimated Remediation Costs
Average estimated costs across ZIP codes served by this system
Based on national averages for common remediation projects. Actual costs vary by property. Only issues flagged by EPA, FEMA, or state data for each ZIP code are included.
System Overview
King County Water District #20 (EPA ID: WA5338950) is a community water system in Washington that serves approximately 38,974 people from surface water sources.
This system provides water to 62 ZIP codes across 1 community.
Average Home Safety Score: A (95/100)
Based on water quality violations, lead levels, and radon risk across all ZIP codes served by this system.
Violation History
Recent Violations
| Date | Contaminant | Type | Status |
|---|---|---|---|
| July 1, 2024 | Surface Water Treatment Rule | Monitoring | Resolved |
Contaminants Detected
The following contaminants have been flagged in EPA records for this water system:
| Contaminant | Category | Violations | Health-Based |
|---|---|---|---|
| Surface Water Treatment Rule | Treatment Failure | 1 | No |
Lead & Copper
EPA Lead and Copper Rule sampling data for ZIP codes served by this system:
| ZIP Code | Lead Level | Exceeds Limit | Sample Date |
|---|---|---|---|
| 98148 | 0.0035 mg/L | No | N/A |
Radon Risk in Service Area
Dominant radon zone for ZIP codes served by this system: Zone 3 (Low Risk)
Need help with your water quality?
Typical cost: Water test: typically $20–$50 (DIY kit) · Professional inspection: $150–$400
Find the Right Water FilterFree tip: Let cold water run for 2 minutes before drinking — this helps flush lead from your pipes.
ZIP Codes Served
Coverage: 6 ZIP codes confirmed via EPA Community Water System Service Area Boundaries v3 plus 56 additional ZIPs inferred from SDWIS registry data. The EPA-confirmed set is the most reliable; SDWIS-inferred entries may be narrower than the real deployment area.
This system serves 62 ZIP codes:
98101 · 98102 · 98103 · 98104 · 98105 98106 · 98107 · 98108 · 98109 · 98111 98112 · 98113 · 98114 · 98115 · 98116 98117 · 98118 · 98119 · 98121 · 98122 98124 · 98125 · 98126 · 98127 · 98129 98131 · 98132 · 98133 · 98134 · 98136 98138 · 98139 · 98141 · 98144 · 98145 98146 · 98148 · 98154 · 98155 · 98158 98160 · 98161 · 98164 · 98165 · 98166 98168 · 98170 · 98171 · 98174 · 98175 98177 · 98178 · 98181 · 98185 · 98188 98189 · 98190 · 98191 · 98194 · 98195 98198 · 98199
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for King County Water District #20 (WA5338950) on EPA.gov.
Frequently Asked Questions
Is King County Water District #20 water safe to drink?
King County Water District #20 has only monitoring/reporting violations, which are procedural in nature. The system meets federal health-based standards.
How many people does King County Water District #20 serve?
King County Water District #20 serves approximately 38,974 people across 62 ZIP codes in Washington.
Where does King County Water District #20 get its water?
The primary water source is surface water.
Consumer Confidence Report (CCR)
Every community water system is required to provide an annual Consumer Confidence Report (CCR) to customers. The most recent report is from 2025.
Contact Your Water Utility
Public-record contact information for the water utility serving this system. Use these channels to request water quality reports, ask about service, or report issues directly.
Contact information from King County Water District 20 Consumer Confidence Report.
ZipCheckup is not affiliated with this water utility, does not act as its agent, and does not provide customer support for it. Contact details shown are public-record information from CCR filings. For service issues, contact the utility directly using the information above.
Water Source & Treatment
Where this water originates and how it's treated before reaching your tap.
Source: King County Water District 20 Consumer Confidence Report.
ZipCheckup is not affiliated with this water utility. Treatment and source data are sourced from the utility's published CCR filings.
Washington's SWAP, conducted by the Washington State Department of Health Office of Drinking Water, gives all surface waters in Washington a susceptibility rating of 'high' regardless of contaminant detection.
Treatment regime
How this utility classifies its treatment process and what each reported treatment chemical does.
Treatment chemicals and what each one does
Chemical names are reported verbatim by the utility. Purpose categories are ZipCheckup annotations based on standard drinking-water treatment practice.
Watershed exposure sources reported
Land-use and natural conditions identified in the utility's source-water assessment as potential contamination sources upstream of treatment.
Treatment classification and chemical list sourced from King County Water District 20 Consumer Confidence Report.
Treatment intensity is a ZipCheckup-derived classification based on the chemicals and processes the utility reports. Chemicals and contamination sources are taken verbatim from the utility's CCR filing. Routine federal monitoring and contaminant testing shown elsewhere on this page determine whether the water meets safety standards, not the treatment classification.
Federal UCMR5 PFAS Monitoring: Tested Clean
This water system was tested under the federal EPA Unregulated Contaminant Monitoring Rule (UCMR5). No PFAS compounds were detected.
Current MCL reflects the lowest state-enforceable limit (NYS 10 ppt for PFOA/PFOS, effective August 2020). The federal final MCL of 4 ppt for PFOA/PFOS (EPA April 2024 rule) is not enforceable until April 2029. Detections above 4 ppt but below 10 ppt are below current MCL but above the future federal limit.
Source: U.S. EPA UCMR5 (Unregulated Contaminant Monitoring Rule, 5th cycle) — per-system federal sampling, 2023–2025. EPA UCMR5 monitoring program →
Lead Service Line Inventory
Service line breakdown reported under the federal Lead and Copper Rule Improvements (LCRI) inventory requirement:
Federal LCRI rule (effective October 2024) requires every public water system to inventory its service lines and complete lead-line replacement within 10 years.
Source: EPA SDWIS Federal Service Line Inventory (Phase 2) · Submitted 2026
ZipCheckup is not affiliated with the utility or state agency. Inventory figures render verbatim from the public LCRI submission cited above; ZipCheckup does not perform inspections or replacements.
How Water Systems Appear in Rankings
Water systems are evaluated by violation history, contaminant detections, and service population. Larger systems with more service connections appear in more rankings.
Frequently Asked Questions
How to cite this page
ZipCheckup. (2026). King County Water District #20 (WA): 1 EPA Violation (2026). https://zipcheckup.com/water-system/wa5338950/
@misc{zipcheckup-water-system-wa5338950,
author = {{ZipCheckup}},
title = {{King County Water District #20 (WA): 1 EPA Violation (2026)}},
year = {2026},
url = {https://zipcheckup.com/water-system/wa5338950/}
}
Data as of April 2026.
What You Can Do
Test your water
Home test kits can detect lead, bacteria, and other contaminants at your tap. Find the right filter →
Check your specific ZIP code
Water quality can vary within a system. View nearest ZIP report →
Contact your utility
King County Water District #20 (EPA ID: WA5338950) - request the latest Consumer Confidence Report or ask about specific contaminants.