Tap Water Results

Is Issaquah, WA tap water safe?

Data: U.S. EPA · How we read the data · How we check it

Summary

Sammamish Plateau Water & Sewer, the largest system here, had PFAS above the 2024 federal limits (PFOS) in EPA's 2023–2025 testing.

Is it an emergency? No: PFAS limits are about years of exposure, not a glass of water, and nothing in EPA's data calls for you to stop drinking the water today. If your utility issues a boil-water or do-not-drink notice, follow it.

3 public water systems serve parts of Issaquah. The largest, Sammamish Plateau Water & Sewer, serves 79,362 people, and one system here had PFAS above a federal limit. Your water bill names your system.

Largest system

Sammamish Plateau Water & Sewer

79,362 people · Purchased surface water · EPA ID WA5340900

Buys treated water from Northeast Sammamish Sewer & Water District, Issaquah Water System, Ames Lake Water Association Inc, Union Hill Water Association Inc.

PFASHighest averageLimitStatus
PFOA
Not detected
–4 pptNot detected
PFOS
Above limit
9.65 ppt4 pptAbove limit
PFHxS
Rounds to the limit
14.8 ppt10 pptRounds to the limit
PFNA
Not detected
–10 pptNot detected
HFPO-DA (GenX)
Not detected
–10 pptNot detected

ppt = parts per trillion. "Highest average" is the highest average at any of the system's entry points, the way EPA compares results with the limits.

For context: the PFOS average is higher than at 96% of the Washington systems EPA tested.

Lead: 1.7 ppb at the 90th percentile (Dec 2025, and 9 in 10 homes sampled were at or below it) Below action level
Health-based violations since 2016: 0

Full Sammamish Plateau Water & Sewer results

Across Washington, 20 of 245 water systems EPA tested had PFAS above a 2024 federal limit, and 17 systems were above the lead action level in results from the last five years. Washington results.

Issaquah homes and lead pipes

18%
of homes built before 1980 (Washington 43%, US 50%)
3%
built before 1950 (Washington 14%)
43%
of households rent (Washington 36%)

Lead service lines and lead solder were allowed until 1986, so homes from before then are the ones to check. Renting? Ask your landlord what the service line is made of, because it's their pipe to replace. How to check your own line.

Housing: Census American Community Survey 2020–2024 5-year estimates for Issaquah city (tables B25034, B25003). Estimates for small places have a margin of error.

Which system serves your ZIP code

Based on the ZIP codes each system reported serving. Boundaries don't follow ZIP lines exactly, so your water bill is the final word.

SystemZIP codes in Issaquah
Sammamish Plateau Water & Sewer
79,362 people
98029
Issaquah Water System
43,584 people
98027

Other water systems serving Issaquah

  • Issaquah Water System
    43,584 people · Purchased surface water · Washington · lists this city
    No PFAS above limits
  • Bryan County Rws & Swmd #2
    6,270 people · Surface water · Oklahoma · reported ZIPs here
    Total trihalomethanes (TTHM) violationsAlso: Haloacetic acids (HAA5) violation

How nearby cities compare

CityMain water systemPFASLead (90th pct.)
Sammamish 3 mi
Sammamish Plateau Water & Sewer
Sammamish Plateau Water & SewerAbove limit1.7 ppb
Bellevue 6 mi
City of Bellevue
City of BellevueNone above limits–
Renton 8 mi
City of Renton
City of RentonNone above limits1.9 ppb
Mercer Island 9 mi
City of Mercer Island
City of Mercer IslandNone above limits–
Redmond 10 mi
City of Redmond Water System
City of Redmond Water SystemNone above limits2 ppb
Kirkland 13 mi
Northshore Utility District
Northshore Utility DistrictNone above limits–

Questions

Is Issaquah tap water safe to drink?

Sammamish Plateau Water & Sewer has had no health-based violations since 2016, and EPA testing found PFAS above the 2024 federal limits, which it must meet by 2029. Utility data can't show lead from your own pipes: if your home was built before 1986, test your tap. Your utility's annual Consumer Confidence Report is the official summary.

Who supplies water in Issaquah, WA?

3 public water systems serve parts of Issaquah. The largest is Sammamish Plateau Water & Sewer (79,362 people). Your water bill names your system. The EPA ID is also on your utility's Consumer Confidence Report.

Does Issaquah tap water have PFAS?

Yes. EPA's 2023–2025 testing found entry-point averages above the 2024 federal limits for PFOS at Sammamish Plateau Water & Sewer. Systems have until 2029 to meet them.

Do Issaquah homes have lead pipes?

Census estimates put 18% of Issaquah homes as built before 1980 (Washington: 43%). Lead service lines and lead solder were allowed until 1986, so older homes are more likely to have them. Sammamish Plateau Water & Sewer's service line inventory says what your line is made of. The only way to know for your home is to check the line where it enters the house and test your tap.

Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.