ISSAQUAH WATER SYSTEM

Q: Is ISSAQUAH WATER SYSTEM water safe to drink?

ISSAQUAH WATER SYSTEM (PWS ID: WA5336350) has 257 recorded violations in the EPA SDWIS database. No PFAS contamination was detected in UCMR5 testing. This system serves 43,584 people using Surface Water sources.

Q: What type of violations does ISSAQUAH WATER SYSTEM have?

ISSAQUAH WATER SYSTEM has 257 total violations: 8 health-based violations (MCL exceedances or treatment failures), 247 monitoring/reporting violations, and 0 treatment technique violations. Health-based violations indicate contaminant levels exceeded EPA safe limits.

Q: Has PFAS been detected in ISSAQUAH WATER SYSTEM water?

No. ISSAQUAH WATER SYSTEM was tested for PFAS under the EPA's UCMR5 monitoring program and no PFAS contamination was detected.

Q: What water source does ISSAQUAH WATER SYSTEM use?

ISSAQUAH WATER SYSTEM uses Surface Water as its primary water source. It is classified as a Community Water System (CWS), serving residential populations year-round.

Q: Where does this data come from?

All data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS tracks compliance for all public water systems regulated under the Safe Drinking Water Act.

Reviewed byPlainWater Editorial, Drinking Water Quality Editorial Team · June 4, 2026

PWS ID: WA5336350 · ISSAQUAH, Washington 98027-1307

ISSAQUAH WATER SYSTEM serves 43,584 people in ISSAQUAH, Washington using Surface Water water sources. It has 257 recorded EPA violations, including 8 health-based violations. No PFAS contamination was detected in UCMR5 testing.

Water Quality Snapshot: ISSAQUAH WATER SYSTEM

ISSAQUAH WATER SYSTEM is a local-owned community water system that delivers drinking water to 43,584 residents in ISSAQUAH, Washington (King County) through 14,979 service connections. Its water is drawn from surface water sources. EPA's Safe Drinking Water Information System records 257 total violations for this system , of which 8 (3%) are health-based — meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 247 monitoring and reporting violations are on file. The most recent violation on record dates to 2015.

The most frequently cited contaminant at this system is OXAMYL, recorded in 24 violations (MR). This system was sampled under EPA's UCMR5 PFAS monitoring program and no PFAS compounds were detected above the minimum reporting level.

Across Washington, EPA tracks 4,557 public water systems serving 9,736,844 people, with 314,648 cumulative violations and 20,590 health-based violations on record. About 92% of systems in the state carry at least one violation, and state-wide the average per system is 69 violations. ISSAQUAH WATER SYSTEM's 257 violations sit above the Washington average. Statewide, 98 of 247 UCMR5-tested systems have reported PFAS detections (39.7%). All figures above are sourced directly from EPA SDWIS and UCMR5 public data releases and are updated as EPA publishes new reporting cycles.

Population Served

43,584

Total Violations

257

Health-Based Violations

Water Source

Surface Water

System Details

System Type: Community
Owner Type: Local
Connections: 14,979
County: King
School/Daycare: No
MCL Violations: 8
Monitoring Violations: 247
Treatment Tech Violations: 0

Violation History

Contaminant violations recorded by EPA.

Contaminant	Category	Count	Latest
OXAMYL	MR	24	2005
Aldicarb sulfone	MR	24	2005
Aldicarb	MR	24	2005
Aldicarb sulfoxide	MR	24	2005
Carbofuran	MR	24	2005
Coliform (TCR)	MCL	8	2003
Pentachlorophenol	MR	8	2002
Benzo(a)pyrene	MR	4	2002
Hexachlorocyclopentadiene	MR	4	2002
2,4,5-TP	MR	4	2002
Heptachlor epoxide	MR	4	2002
Chlordane	MR	4	2002
BHC-GAMMA	MR	4	2002
Toxaphene	MR	4	2002
Methoxychlor	MR	4	2002
Simazine	MR	4	2002
LASSO	MR	4	2002
Di(2-ethylhexyl) phthalate	MR	4	2002
Picloram	MR	4	2002
Endrin	MR	4	2002
Heptachlor	MR	4	2002
Atrazine	MR	4	2002
Di(2-ethylhexyl) adipate	MR	4	2002
Dinoseb	MR	4	2002
Dalapon	MR	4	2002
HEXACHLOROBENZENE	MR	4	2002
trans-1,2-Dichloroethylene	MR	2	2002
1,2-Dichloroethane	MR	2	2002
1,1,1-Trichloroethane	MR	2	2002
1,2-Dichloropropane	MR	2	2002

PFAS Testing Results (UCMR5)

Results from EPA's Fifth Unregulated Contaminant Monitoring Rule. 0 of 300 samples detected PFAS.

Contaminant	Date	Result	MRL	Status
NMeFOSAA	9/4/2024	<0.006 µg/L	0.006 µg/L	Not Detected
NEtFOSAA	9/4/2024	<0.005 µg/L	0.005 µg/L	Not Detected
PFTrDA	9/4/2024	<0.007 µg/L	0.007 µg/L	Not Detected
PFTA	9/4/2024	<0.008 µg/L	0.008 µg/L	Not Detected
lithium	9/4/2024	<9 µg/L	9 µg/L	Not Detected
4:2 FTS	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFUnA	9/4/2024	<0.002 µg/L	0.002 µg/L	Not Detected
lithium	9/4/2024	<9 µg/L	9 µg/L	Not Detected
PFEESA	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFHxA	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFHpS	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFDoA	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFPeS	9/4/2024	<0.004 µg/L	0.004 µg/L	Not Detected
NFDHA	9/4/2024	<0.02 µg/L	0.02 µg/L	Not Detected
PFTA	9/4/2024	<0.008 µg/L	0.008 µg/L	Not Detected
PFMBA	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFPeA	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFMPA	9/4/2024	<0.004 µg/L	0.004 µg/L	Not Detected
8:2 FTS	9/4/2024	<0.005 µg/L	0.005 µg/L	Not Detected
6:2 FTS	9/4/2024	<0.005 µg/L	0.005 µg/L	Not Detected
PFBS	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFTrDA	9/4/2024	<0.007 µg/L	0.007 µg/L	Not Detected
NEtFOSAA	9/4/2024	<0.005 µg/L	0.005 µg/L	Not Detected
NMeFOSAA	9/4/2024	<0.006 µg/L	0.006 µg/L	Not Detected
PFBA	9/4/2024	<0.005 µg/L	0.005 µg/L	Not Detected
HFPO-DA	9/4/2024	<0.005 µg/L	0.005 µg/L	Not Detected
11Cl-PF3OUdS	9/4/2024	<0.005 µg/L	0.005 µg/L	Not Detected
9Cl-PF3ONS	9/4/2024	<0.002 µg/L	0.002 µg/L	Not Detected
PFHpA	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFHxS	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFNA	9/4/2024	<0.004 µg/L	0.004 µg/L	Not Detected
PFOS	9/4/2024	<0.004 µg/L	0.004 µg/L	Not Detected
PFOA	9/4/2024	<0.004 µg/L	0.004 µg/L	Not Detected
PFDA	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
ADONA	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFBA	9/4/2024	<0.005 µg/L	0.005 µg/L	Not Detected
PFMBA	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFPeA	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFMPA	9/4/2024	<0.004 µg/L	0.004 µg/L	Not Detected
PFUnA	9/4/2024	<0.002 µg/L	0.002 µg/L	Not Detected
PFHxA	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFOA	9/4/2024	<0.004 µg/L	0.004 µg/L	Not Detected
PFOS	9/4/2024	<0.004 µg/L	0.004 µg/L	Not Detected
ADONA	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFHxS	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
PFHpA	9/4/2024	<0.003 µg/L	0.003 µg/L	Not Detected
HFPO-DA	9/4/2024	<0.005 µg/L	0.005 µg/L	Not Detected
PFPeS	9/4/2024	<0.004 µg/L	0.004 µg/L	Not Detected
lithium	9/4/2024	<9 µg/L	9 µg/L	Not Detected
PFNA	9/4/2024	<0.004 µg/L	0.004 µg/L	Not Detected

Verify This Water System

The figures above are aggregated from EPA's public databases. To verify the underlying records — or to file a complaint, request a Consumer Confidence Report, or check current monitoring status — go directly to the federal and state regulators that enforce the Safe Drinking Water Act for ISSAQUAH WATER SYSTEM.

Federal Source of Truth

EPA SDWIS — Federal Reports

EPA's Safe Drinking Water Information System (SDWIS) holds the federal compliance record for every regulated public water system. Open the system-level report by PWS ID:

View PWS ID WA5336350 on SDWIS

Source: EPA SDWIS Federal Reports Search

State Regulator

Washington Drinking Water Authority

Washington State Department of Health — Office of Drinking Water is the primacy agency that licenses and inspects ISSAQUAH WATER SYSTEM under EPA-delegated authority.

Open WA regulator portal

Source: Washington State Department of Health — Office of Drinking Water

Violation Timeline

Each row links to the EPA SDWIS public record for verification. Cross-reference the contaminant code on EPA's federal report to see violation dates, return-to-compliance status, and enforcement actions.

Year (latest)	Contaminant	Category	Count	EPA Record
2015	Consumer Confidence Rule	Other	1	SDWIS / WA5336350 / 7000
2005	OXAMYL	MR	24	SDWIS / WA5336350 / 2036
2005	Aldicarb sulfone	MR	24	SDWIS / WA5336350 / 2044
2005	Aldicarb	MR	24	SDWIS / WA5336350 / 2047
2005	Aldicarb sulfoxide	MR	24	SDWIS / WA5336350 / 2043
2005	Carbofuran	MR	24	SDWIS / WA5336350 / 2046
2003	Coliform (TCR)	MCL	8	SDWIS / WA5336350 / 3100
2002	Pentachlorophenol	MR	8	SDWIS / WA5336350 / 2326
2002	Benzo(a)pyrene	MR	4	SDWIS / WA5336350 / 2306
2002	Hexachlorocyclopentadiene	MR	4	SDWIS / WA5336350 / 2042
2002	2,4,5-TP	MR	4	SDWIS / WA5336350 / 2110
2002	Heptachlor epoxide	MR	4	SDWIS / WA5336350 / 2067
2002	Chlordane	MR	4	SDWIS / WA5336350 / 2959
2002	BHC-GAMMA	MR	4	SDWIS / WA5336350 / 2010
2002	Toxaphene	MR	4	SDWIS / WA5336350 / 2020

How ISSAQUAH WATER SYSTEM Compares

Cross-reference this system's record against state averages and the federal MCL framework for context.

Metric	ISSAQUAH WATER SYSTEM	Washington avg	Federal benchmark
Total violations	257	69	SDWA compliance — any non-zero count is a recorded breach
Health-based violations	8	4.5	Indicates a contaminant exceeded a federal MCL
PFAS detection	None	39.7%	EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt
Population served	43,584	2,137	Sizing context for compliance burden

Sources: EPA SDWIS and EPA National Primary Drinking Water Regulations (40 CFR Part 141). State averages computed across 4,557 regulated public water systems in Washington.

Federal MCL reference — Safe Drinking Water Act thresholds ▼

Contaminant	Federal MCL / Action Level	Note
Lead	0 mg/L (Action Level: 0.015 mg/L)	Lead and Copper Rule treatment technique
Arsenic	0.010 mg/L (10 ppb)	Health-based MCL since 2006
Total Coliform	Treatment technique (RTCR)	Indicator organism, monitoring trigger
PFOA / PFOS (PFAS)	4.0 ppt each (final 2024 rule)	Compliance deadline 2029
Nitrate (as N)	10 mg/L	Acute health risk for infants

Frequently Asked Questions

Is ISSAQUAH WATER SYSTEM water safe to drink? ▼

ISSAQUAH WATER SYSTEM (PWS ID: WA5336350) has 257 recorded violations in the EPA SDWIS database. No PFAS contamination was detected in UCMR5 testing. This system serves 43,584 people using Surface Water sources.

How many people does ISSAQUAH WATER SYSTEM serve? ▼

ISSAQUAH WATER SYSTEM serves 43,584 people in ISSAQUAH, Washington. It is a Local-owned system using Surface Water water sources with 14,979 service connections.

What type of violations does ISSAQUAH WATER SYSTEM have? ▼

ISSAQUAH WATER SYSTEM has 257 total violations: 8 health-based violations (MCL exceedances or treatment failures), 247 monitoring/reporting violations, and 0 treatment technique violations. Health-based violations indicate contaminant levels exceeded EPA safe limits.

Has PFAS been detected in ISSAQUAH WATER SYSTEM water? ▼

No. ISSAQUAH WATER SYSTEM was tested for PFAS under the EPA's UCMR5 monitoring program and no PFAS contamination was detected.

What water source does ISSAQUAH WATER SYSTEM use? ▼

ISSAQUAH WATER SYSTEM uses Surface Water as its primary water source. It is classified as a Community Water System (CWS), serving residential populations year-round.

Where does this data come from? ▼

All data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS tracks compliance for all public water systems regulated under the Safe Drinking Water Act.

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Data Sources: EPA Safe Drinking Water Information System (SDWIS), Q4 2025. PFAS data from EPA UCMR5 monitoring program (2023-2025). This data is provided for informational purposes only.

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