Is MERCER ISLAND CITY OF's water safe to drink?
MERCER ISLAND CITY OF has a health-based violation on record, but none in the last five years - an older issue, not necessarily a current one. 31,057 people get their water from it, across 9,807 connections.
How this compares nationally
5 total violations and 1 health-based ones put MERCER ISLAND CITY OF at the 33th percentile nationally for violation burden, rank 8,667 of 12,903.
How MERCER ISLAND CITY OF compares within WA
Among the 322 WA systems in this dataset, the average is 3.7 health-based violations - MERCER ISLAND CITY OF's 1 is at or below that. See the lead and copper guide for why lead counts differently.
Most recent violation on record
The last violation EPA has on record for MERCER ISLAND CITY OF is from 1992-01-12 (health-based: 1992-01-01). Last reported to EPA: 06/19/2026.
What kind of problem, specifically
MERCER ISLAND CITY OF's flagged contaminants and rule violations, grouped by what they actually mean for a filter choice rather than left as EPA's raw code list:
- Microbial contamination / treatment technique - flagged from: Coliform (TCR)
The most severe category on record is microbial contamination / treatment technique, which points toward a microbial-class filter if you want to address it directly.
What this data is and is not
This is what MERCER ISLAND CITY OF reported to its state primacy agency and EPA under the Safe Drinking Water Act - real regulatory record, not a lab test of your specific tap. This record - 1 health-based violation on file for MERCER ISLAND CITY OF - stops at the meter and cannot see household plumbing on the other side of it. The guide to what this data misses covers that gap.