State profile · EPA SDWIS + UCMR5
Washington Drinking Water Quality
4,557 SDWIS-listed public water systems serve 9,736,844 people across Washington. Violation rates use that full inventory; PFAS rates use only the UCMR5-tested subset.
- 4,557
- SDWIS water systems
- 314,648
- Total violations
- 92.1%
- SDWIS systems w/ a violation
- 26.7%
- UCMR5 PFAS rate (247 tested)
The verdict
9,736,844 people served via SDWIS-listed systems - larger served population (> 5,131,439). According to EPA SDWIS population served, Washington ranks #11 of 66 states and territories by people served through public water systems.
- #11 of 66
- Population · states corpus
- 314,648
- Total EPA violations on record
- 7%
- Health-based (MCL / treatment)
- 92.1%
- SDWIS systems with ≥1 violation
SDWIS violation % and UCMR5 PFAS % use different denominators (full inventory vs tested subset). Population ordinal uses SDWIS population served.
Washington standing, low SDWIS violation-rate third
Washington is in the lower third of jurisdictions by violation rate (92.1%; lower-third rate (≤ 92.5%)). That is a relative placement among peers, not a claim that most systems are clean - 4,199 of 4,557 still carry ≥1 record. Population served is large (9,736,844; larger served population (> 5,131,439)), so household exposure scale sits behind inventory and rate. Health-based share is only 7% - almost all of this trail is monitoring/reporting rather than MCL exceedance. UCMR5 PFAS detection is 26.7% on the tested subset (mid UCMR5 detection (≤ 35.3%)) - a different denominator from the SDWIS violation rate. Systems listed below are ranked by population served or violation count; pair rate with inventory size before reading exposure scale.
Nationwide similar states
Nearest by SDWIS violation rate
Nearest by population served
Health-based share of this violation record
EPA SDWIS classifications for Washington's 314,648 recorded violations.
Washington vs nearest violation-rate peers
Share of SDWIS-listed systems with at least one recorded violation; peers are nearest by absolute rate distance, not a fixed top-seven list.
- WA
Washington
92.1 % of systems
- GA
Georgia
92.1 % of systems
- LA
Louisiana
92.5 % of systems
- NV
Nevada
92.5 % of systems
- CO
Colorado
92.6 % of systems
What this shows Washington's rate is 92.1% (4,199 of 4,557 systems; lower-third rate (≤ 92.5%)). This is a comparison of recorded SDWIS violations, not a measure of current water safety.
Washington vs all jurisdictions by SDWIS system inventory
Where this state's public water system count sits among every state and territory on PlainWater
4,557 11th of 66 higher than 55 of 66 jurisdictions
States and territories, banded by SDWIS-listed public water system count
Each bar is a band; taller bars hold more jurisdictions. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source EPA SDWIS state aggregates · 2026-05-15
Largest Water Systems
Most Violations
Counties in Washington
Showing top 30 of 39 counties.
Context: Check your water system · methodology · all states
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.