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Counties → Washington

King County, Washington

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.

0% 20% 40% 60% 80% 100% Grant · lowest Spokane · near Mason · near Wahkiakum · highest 69.8% 96.1% 96.3% 96.8% 97.1% 97.6% 100%

Source: EPA SDWIS (county aggregates) As of 2026-05-15

Water Systems

System Name Population Violations PFAS
Seattle Public Utilities 1,091,904 29 Clean
Bellevue City Of 317,330 11 Clean
Kent Water Department 166,421 37 Detected
Redmond Water System City Of 163,335 2 Detected
Lakehaven Water and Sewer District 118,273 78 Detected
Highline Water District 115,950 9 Clean
Auburn City of 113,095 127 Detected
Renton City Of 107,119 59 Detected
Northshore Utility District 105,105 5 Clean
Sammamish Plateau Water & Sewer 79,362 77 Detected
Kirkland City Of 67,107 1 Clean
Soos Creek Water & Sewer District 64,534 1 Clean
Woodinville Water District 59,873 5 Clean
Covington Water District 52,276 21 Detected
Port of Seattle/Seatac Airport 49,483 14 Clean
Tukwila Water Department 45,374 0 Clean
Issaquah Water System 43,584 257 Clean
King County Water District #20 38,974 3 Clean
Bothell Water City Of 33,643 1 Clean
North City Water District 31,744 4 Clean
Mercer Island City Of 30,689 8 Clean
Cedar River Water & Sewer District 28,671 0 Detected
Lake Meridian Water District 24,231 9 Clean
Enumclaw Water Department 23,276 39 Clean
King County Water District No 90 20,100 262 Clean
King County Water District #125 17,546 7 Clean
King County Water District #49 16,065 9 Clean
Coal Creek Utility District 15,989 12 Clean
Snoqualmie Water 15,848 39 Clean
Skyway Water & Sewer 12,036 4 Clean
Duvall City Of 10,267 6 Clean
Union Hill Water Association Inc 8,720 312 Clean
NE Sammamish Sewer & Water District 8,516 19 Clean
Pacific City Of 7,925 16 Clean
North Bend City Of 7,228 5 Clean
Sallal Water Association Inc 6,600 15 Clean
Snoqualmie Pass Utility District 5,805 322 Clean
King County Water District #54 5,037 20 Clean
Stevens Pass Water System 4,053 35 Clean
King County Water District 119 3,796 3 Clean
Water District 19 3,723 572 Clean
Ames Lake Water Assoc Inc 3,224 178 -
Algona Water Dept 3,180 13 -
Lake Forest Park Water District 3,171 9,527 Clean
Fall City Water Dist. #127 2,987 15 -
Black Diamond Water Dept 2,420 194 -
Carnation Water System City Of 2,400 12 -
Cherokee Bay Community Club Inc 2,400 25 -
Mirrormont 2,083 31 -
Heights Water 2,051 6 Clean

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.

4 peers

Similar violation load

Nearest cross-state counties by cumulative SDWIS violation count (all systems in the county).

4 peers

Read our methodology · Check your water system - how this data is sourced, computed, and verified.

Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This page draws directly on EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.