Is Mercer Island, WA tap water safe?
Data: U.S. EPA · How we read the data · How we check it
Summary
No federal limits exceeded in EPA data for City of Mercer Island.
City of Mercer Island supplies Mercer Island (31,057 people).
Water system
City of Mercer Island
31,057 people · Purchased surface water · EPA ID WA5353640
Buys treated water from Seattle Public Utilities.
| PFAS | Highest average | Limit |
|---|---|---|
| PFOA Not detected | – | 4 ppt |
| PFOS Not detected | – | 4 ppt |
| PFHxS Not detected | – | 10 ppt |
| PFNA Not detected | – | 10 ppt |
| HFPO-DA (GenX) Not detected | – | 10 ppt |
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.
Lead: no results reported
Health-based violations since 2016: 0
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.
Mercer Island homes and lead pipes
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 Mercer Island city (tables B25034, B25003). Estimates for small places have a margin of error.
How nearby cities compare
| City | PFAS | Lead (90th pct.) |
|---|---|---|
| Bellevue 4 mi City of Bellevue | None above limits | – |
| Renton 6 mi City of Renton | None above limits | 1.9 ppb |
| Seattle 7 mi Seattle Public Utilities | None above limits | 1.6 ppb |
| Burien 8 mi Highline Water District | None above limits | 1.4 ppb |
| Issaquah 9 mi Sammamish Plateau Water & Sewer | Above limit | 1.7 ppb |
| Sammamish 9 mi Sammamish Plateau Water & Sewer | Above limit | 1.7 ppb |
Mercer Island ZIP codes (1)
- 98040
Questions
Is Mercer Island tap water safe to drink?
City of Mercer Island has had no health-based violations since 2016. 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 Mercer Island, WA?
City of Mercer Island, which serves 31,057 people.
Does Mercer Island tap water have PFAS?
None detected above EPA's reporting limits. City of Mercer Island had no PFAS detected in EPA's 2023–2025 testing. "Not detected" means below the reporting limit (about 2 to 20 ppt), not proven zero.
Do Mercer Island homes have lead pipes?
Census estimates put 61% of Mercer Island 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. City of Mercer Island'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.