County profile · EPA SDWIS + UCMR5
King County, Washington
217 SDWIS-listed public water systems serve 3,193,095 people in King County. Violation rates use that full inventory; PFAS rates use only the UCMR5-tested subset.
- 217
- SDWIS water systems Larger third of counties
- 20,636
- Total violations Upper third of counties
- 96.8%
- SDWIS systems w/ a violation Middle third of counties
- 18.2%
- UCMR5 PFAS rate (44 tested) Middle third of counties with tests
SDWIS compliance plate
Sheet WA033 · King County 217 sys · 20,636 viol · #10/3254
VIOL-SEVERE · HEALTH-LOW · RANK-TOP · PHOTO-FINISH · PFAS-LOW · SRC-GW · SYS-LARGE · BOOK-FULL
- VIOL-SEVERE 96.8% flagged
- HEALTH-LOW 4.0% health
- RANK-TOP #10/3254
- PHOTO-FINISH ±0.3 pp
- PFAS-LOW 18.2% detect
- SRC-GW GW lead 82%
- SYS-LARGE 217 systems
- BOOK-FULL 7/7 fields
Nearest flagged-rate peer: Mason County (+ 0.3 pp flagged-rate)
According to EPA SDWIS county population served used on /counties, King County ranks #10 of 3,254 counties by people served, and #1 of 39 counties in Washington. See methodology · corpus placement.
King County standing, mid-flagged corpus third
Flagged-system rate 96.8% is in the corpus middle third (≤ 100.0% flagged) across 2,973 counties with ≥3 SDWIS systems . Health-based share 4.0% is health-based share at or below the lower third (≤ 10.3%) . UCMR5 detect rate 18.2% is UCMR5 detect rate in the tested-pool middle third (≤ 33.3%) . Population served ranks #10 of 3,254 · #1 of 39 in Washington.
Flagged-rate neighbourhood around King County
Lowest/highest poles plus in-state counties nearest King County on % of SDWIS systems with ≥1 violation. Full ladder: /counties.
Water Systems
Compare beyond Washington
Mid-flagged peers for King County
Cross-state counties nearest King County on flagged-system share (96.8%) and cumulative violation count (20,636). In-state neighbours stay on the compliance plate above.
Similar flagged-system rate
Nearest cross-state counties by % of SDWIS systems with at least one violation on record.
Similar violation load
Nearest cross-state counties by cumulative SDWIS violation count (all systems in the county).
Read our methodology · Check your water system - how this data is sourced, computed, and verified.
Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.