Issaquah Water System
EPA ID: WA5336350 · 43,584 people served · 6 ZIP codes
ZipCheckup's reading of EPA SDWIS for Issaquah Water System (WA5336350): no EPA violations recorded in the last five years. Throughout five consecutive years of federal water monitoring, Issaquah Water System recorded zero violations - solid performance for a utility serving 43,584 people.
Data: EPA SDWIS
Service Area Map
Coverage area for Issaquah Water System Source: EPA SDWIS service area boundaries.
Service area boundary - Grade A
Service Area Demographics
The Issaquah Water System serves a community with a median household income of $152,726 and an estimated 146,393 residents across its service area.
🌊 Where Does Your Water Come From?
Issaquah Water System'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
PFAS Detected in Service Area
PFAS ("forever chemicals") have been detected in water serving this system's area. 7 detections recorded. 2 exceed federal EPA limits (4 ppt for PFOA/PFOS).
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
Issaquah Water System (EPA ID: WA5336350) is a community water system in Washington that serves approximately 43,584 people from surface water sources.
This system provides water to 6 ZIP codes across 5 communities.
ZIP-Area Home Safety Context: A (98/100)
This is the average Home Safety Score for 1 of 6 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
EPA Lead and Copper Rule evidence attributed directly to this water system:
| Lead Level | Exceeds Action Level | Sample Date |
|---|---|---|
| 0.001 mg/L | No | N/A |
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.
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for Issaquah Water System (WA5336350) on EPA.gov.
Frequently Asked Questions
Is Issaquah Water System water safe to drink?
The accepted 2026Q2 ECHO snapshot contains zero violation records for Issaquah Water System 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 Issaquah Water System serve?
Issaquah Water System serves approximately 43,584 people across 6 ZIP codes in Washington.
Where does Issaquah Water System 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 →
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.
- #39 / 50 Highest Exposure Burden (Washington)
Frequently Asked Questions
How to cite this page
ZipCheckup. (n.d.). Issaquah Water System, WA: Serves 44K People. https://zipcheckup.com/water-system/wa5336350/
@misc{zipcheckup-water-system-wa5336350,
author = {{ZipCheckup}},
title = {{Issaquah Water System, WA: Serves 44K People}},
year = {n.d.},
url = {https://zipcheckup.com/water-system/wa5336350/}
}