City of Mercer Island
EPA ID: WA5353640 · 31,057 people served · 1 ZIP code
ZipCheckup's reading of EPA SDWIS for City of Mercer Island (WA5353640): no EPA violations recorded in the last five years. Water monitoring history at City of Mercer Island shows a clean slate - EPA tracking over the past five years turned up no violations, and 31,057 residents continue to receive fully compliant service.
Data: EPA SDWIS
Service Area Map
Coverage area for City of Mercer Island Source: EPA SDWIS service area boundaries.
Service area boundary - Grade A
Service Area Demographics
The City of Mercer Island serves a community with a median household income of $202,359 and an estimated 25,282 residents across its service area. Approximately 67% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
🌊 Where Does Your Water Come From?
City of Mercer Island'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 70th percentile nationally for proximity to Superfund (NPL) sites.
Infrastructure Risk
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
City of Mercer Island (EPA ID: WA5353640) is a community water system in Washington that serves approximately 31,057 people from surface water sources.
This system serves ZIP code 98040 in Mercer Island.
ZIP-Area Home Safety Context: A (100/100)
This is the average Home Safety Score for 1 of 1 service-area ZIP codes with all required score domains observed. It is not a grade for the water utility.
Model 4.0.0 uses SDWIS identity plus accepted ECHO SDWA lifecycle-based water compliance, the UCMR 5 PFAS MCL screen, EPA radon zone, and annual EPA AirData AQI across three equally weighted domains. Missing required evidence suppresses the score.
Violation History
Lead & Copper
No reported lead measurement appears for this PWSID in the accepted LCR snapshot. Absence of a reported measurement is not a measured zero.
No copper action-level exceedance record appears for this PWSID in the accepted LCR snapshot. This does not establish a clean copper measurement.
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: Service area ZIP codes sourced from EPA Community Water System Service Area Boundaries v3 (March 2026 release). These ZIPs reflect the actual deployment footprint recorded by WA or modeled from parcel and building-footprint data.
- 98040 - Mercer Island
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for City of Mercer Island (WA5353640) on EPA.gov.
Frequently Asked Questions
Is City of Mercer Island water safe to drink?
The accepted 2026Q2 ECHO snapshot contains zero violation records for City of Mercer Island in the inclusive 2021-2026 record-year window. This is a compliance-record finding, not a guarantee about water at a specific tap.
How many people does City of Mercer Island serve?
City of Mercer Island serves approximately 31,057 people across 1 ZIP code in Washington.
Where does City of Mercer Island get its water?
The primary water source is surface water.
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 →
Frequently Asked Questions
How to cite this page
ZipCheckup. (n.d.). City of Mercer Island, WA: Serves 31K People. https://zipcheckup.com/water-system/wa5353640/
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