Issaquah, WA Water Quality (ZIP 98027)

Quick Answers

Is ZIP 98027 tap water safe to drink? Water for ZIP 98027 shows high PFAS contamination. EPA testing found a peak of 600 ppt, above the EPA's 4 ppt enforceable limit. A reverse osmosis or certified PFAS filter is strongly recommended.

What filter should I use in 98027? A reverse osmosis system (NSF/ANSI 58) removes 90%+ of PFAS, lead, and arsenic. For smaller households, a pitcher certified to NSF-53 for PFAS (ZeroWater, PUR PLUS) works. Standard Brita cartridges are not certified for PFAS.

ZIP 98027 Water Quality Summary

EPA testing has detected PFAS "forever chemicals" in the water system serving ZIP 98027 (Issaquah, WA). Monitoring found a peak of 600 ppt across 1 system, averaging 183.26 ppt over 5 detected compounds. These levels come from individual EPA UCMR 5 water samples (2023-2025). The EPA's 4 ppt limit for PFOA and PFOS is enforced on a running annual average, so a sample above it shows real exposure but is not by itself a violation.

Contamination Level: HIGH – High contamination – multiple PFAS compounds detected at levels significantly above EPA safety thresholds.

Top Detected Compounds in ZIP 98027

• PFOS: 600 ppt (exceeds the EPA 4 ppt limit)
• PFHXS: 241 ppt (exceeds the EPA 10 ppt limit)
• PFNA: 28 ppt (exceeds the EPA 10 ppt limit)
• PFHPA: 25.8 ppt (exceeds the EPA 10 ppt limit)
• PFOA: 21.5 ppt (exceeds the EPA 4 ppt limit)

Lead in ZIP 98027 Water

EPA Lead and Copper Rule testing recorded 16 lead samples for the system serving 98027, with a 90th-percentile high of 0.0053 mg/L (within the EPA 0.015 mg/L action level). There is no safe level of lead for children; homes built before 1986 should use a certified NSF/ANSI 53 lead filter.

EPA Violations Affecting ZIP 98027

The water system serving 98027 has 1 health-based EPA Safe Drinking Water Act violation on record, including Revised Total Coliform Rule. A health-based violation means a contaminant exceeded its federal limit or required treatment was not applied.

About the Data

Source: EPA UCMR5 monitoring (2023-2025), Lead and Copper Rule samples, and SDWIS violation records tied to the water system that serves 98027 in Issaquah, WA.

Beyond water: other exposures in Issaquah, WA

Drinking water is one exposure route. These are the other federal datasets that cover ZIP 98027 and King County, WA.

Radon risk in King County, WA

The EPA places King County, WA in Zone 3 - the EPA's lowest-risk category, with a predicted average indoor radon level below 2 pCi/L. Zone maps predict the radon potential of an area from geology and existing indoor readings - they do not describe any individual home. Radon is the leading cause of lung cancer among people who have never smoked, and the only way to know your own level is a test kit.

Lead paint risk in King County, WA

Census figures show 47% of homes in King County, WA were built before 1980, and 16% before 1950. Lead-based paint was banned for residential use in 1978, so older housing stock is the strongest available proxy for lead-paint exposure. This is a statistic about the county's housing, not a test of any particular property - if your home predates 1980, a lead swab test is the way to check.

Air quality in King County, WA

Modelled annual fine-particle pollution (PM2.5) for King County, WA averages 9 µg/m³, within the EPA's annual PM2.5 standard of 9 µg/m³. PM2.5 is the pollution fraction small enough to reach deep into the lungs. These are CDC modelled estimates for the county as a whole, not a reading taken at this ZIP code.

Superfund sites near 98027

There is 1 EPA Superfund (National Priorities List) site within about five miles of 98027: Queen City Farms (about 3.6 miles). Distances are measured from the ZIP code's geographic centre, so the distance from a specific address will differ. Proximity to a listed site is a fact about location - it is not itself evidence of exposure.

Industrial releases near 98027

EPA Toxics Release Inventory data for 2023 records 1 reporting facility within about five miles of 98027, together reporting roughly 39,422 pounds of on-site chemical releases that year. TRI covers facilities above federal reporting thresholds, so smaller sources are not included, and a reported release is not the same as a measured concentration in air or water.