Public water system · WA5336350
ActiveIssaquah Water System
At a glance
Issaquah Water System (PWSID WA5336350) is an active community water system in King County, Washington. It reports serving 43,584 people through 14,979 service connections. Its primary water source is purchased surface water, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in July 2015.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
43,584
Service connections
14,979
Primary source
SWP
Purchased surface water
System type
CWS
Community water system
System record
How does Issaquah Water System compare with other water systems in King County?
By EPA's size categories, Issaquah Water System is a large system (10,001 to 100,000 people). King County has 214 active public water systems. Its population served is about 181% above the county average of 15,523 people per system, and accounts for 1.3% of the 3,321,960 people reported by systems filed under the county. Across Washington, the 4,705 active systems average 2,172 people each. Nationally, the average active community water system reports serving 6,703 people, so Issaquah Water System is about 6.5 times that figure.
What does “community water system” mean?
A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. Washington has 2,392 active community water systems, 51% of the state's 4,705 active systems. Purchased surface water means the system buys surface water from another public water system rather than drawing its own. 130 Washington systems (2.8%) list purchased surface water as their primary source.
Who owns and regulates Issaquah Water System?
EPA lists Issaquah Water System as owned by a local government. The WA state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 58 of the 214 active systems in King County (27%) are also owned by a local government.
Does Issaquah Water System have drinking water violations?
Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in July 2015. The violations listed here began between January 2005 and July 2015. By type: 11 monitoring and reporting and 1 public notice, recordkeeping or other. The contaminant or rule involved most often is Oxamyl (3 of them). EPA lists 12 as resolved. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2015-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Complete Failure to Report · code 71 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Carbofurancode 2046 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Oxamylcode 2036 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Aldicarbcode 2047 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Aldicarb sulfonecode 2044 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Aldicarb sulfonecode 2044 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Aldicarb sulfoxidecode 2043 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Aldicarb sulfoxidecode 2043 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Oxamylcode 2036 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Aldicarb sulfonecode 2044 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Aldicarb sulfoxidecode 2043 | No | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Oxamylcode 2036 | No | Resolved |
The 12 most recent violations in EPA's records, newest first.Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.
Issaquah Water System: frequently asked questions
Who runs Issaquah Water System?
Issaquah Water System (PWSID WA5336350) is a community water system owned by a local government. It is regulated by the WA state drinking water program.
How many people does Issaquah Water System serve?
Issaquah Water System reports serving 43,584 people through 14,979 service connections in King County, Washington.
Where does Issaquah Water System get its water?
EPA SDWIS lists this system's primary water source as purchased surface water. Purchased surface water means the system buys surface water from another public water system rather than drawing its own.
Does Issaquah Water System have any drinking water violations?
Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in July 2015. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.
Is Issaquah Water System's water safe to drink?
AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in July 2015. For current results, consult the system's annual water quality report, EPA ECHO, or the WA state drinking water program.
Where can I find Issaquah Water System's water quality report?
As a community water system, Issaquah Water System must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.
Other water systems in King County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Seattle Public Utilities | King | 1,161,961 | Community | Surface water |
| Bellevue City of | King | 321,349 | Community | Purchased surface water |
| Kent Water Department | King | 166,421 | Community | Purchased surface water |
| Redmond Water System City of | King | 163,335 | Community | Purchased surface water |
| Lakehaven Water and Sewer District | King | 148,809 | Community | Purchased surface water |
| Renton City of | King | 108,091 | Community | Groundwater |
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About this data
Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.
Cite as: AquaCensus, “Issaquah Water System, PWSID WA5336350, Washington”, https://aquacensus.com/water-systems/washington/issaquah-water-system-wa5336350 (data as of October 1, 2026).