Washington Water Quality Rankings 2026: Best & Worst Cities

This page ranks the 4 Washington cities whose water systems we have matched to EPA records. Every city starts at 100 points and loses points for health-based EPA violations in the last five years (SDWIS 2026Q2), its most recent Lead and Copper Rule 90th-percentile result, PFAS detected in EPA's 2023–2026 UCMR5 monitoring, and 2012–2019 compliance samples that averaged near or above a limit. Letters follow fixed bands (A ≥90, B ≥80, C ≥70, D ≥60, F below 60). Cities run from the highest score (Seattle) down to the lowest (Vancouver); ties are ordered by population served. See the full scoring methodology for every deduction and the data vintages.

What your city's grade means

An A or B grade points to water that consistently tests within federal safety limits, while a C suggests moderate issues worth watching and a D or F flags contaminants or compliance problems serious enough to act on. These grades describe system-level water leaving the treatment plant — they can't account for your home's own plumbing, so older houses with lead service lines or fixtures can add contaminants after the water arrives. For a contaminant-by-contaminant view, see the Washington contaminant breakdown or drill into the county-level rankings.

What Washington residents should do

• Find your city in the ranking below and open its full report for its violation history, lead results and PFAS table.
• See how Washington compares against the best-rated and worst-rated cities nationwide.
• Test your home's water if you have concerns — the most common issues involve lead, PFAS, and arsenic.
• Check whether your utility still has lead service lines in Washington — EPA's inventory counts lead pipes by water system, a risk that plant-level grades cannot capture. Read the lead guide for testing and filter options.
• If treatment makes sense for your situation, compare certified water filters matched to the contaminants found in your area.

4 Washington cities have a report on this site. 4 of them are matched to an active EPA-registered community water system (PWSID). Those 4 systems report serving 2,327,316 people in EPA's Safe Drinking Water Information System (SDWIS).

Of all 4 cities Washington cities we can grade from EPA records, 3 cities (75%) grade B or better, 1 sit in the C range and 0 grade D or F. The average score is 89/100.

None of the 4 graded systems has a health-based EPA violation in the last five years; the 0 violations on file in that window are monitoring or reporting lapses.

4 cities have a Lead and Copper Rule 90th-percentile result from 2020 or later: none at 5 ppb or more — every reported result is well below the action level.

EPA's UCMR5 PFAS monitoring (2023–2026) covers 4 cities: PFAS were detected in 3 cities, and PFOA or PFOS reached EPA's 4 ppt limit in 2 cities.

Seattle scores highest (100) and Vancouver lowest (74), a 26-point spread.

Because lead enters water after treatment, the most useful statewide number is the service line inventory Washington utilities filed with EPA (Q2 2026). 2,682 Washington systems inventoried 2,169,608 service lines: 244 confirmed lead plus 6,689 galvanized lines requiring replacement, spread across 25 systems. Another 220,440 lines (10%) are still of unknown material, which EPA counts as possible lead until verified.

Of the 4 city-linked Washington utilities with an inventory on file, 1 reports at least one lead or galvanized-requiring-replacement line and 3 report no lead with most lines verified. SEATTLE PUBLIC UTILITIES, which serves Seattle and 1,161,961 people, is the biggest and reports no lead lines and 100% of lines verified non-lead.

Regionally, the contaminants worth knowing in Washington are lead, nitrates, arsenic, and copper. Lead (EPA action level 0.015 mg/L (15 ppb); health goal 0) harms brain development in children and raises blood pressure and kidney risk in adults; Nitrate (EPA MCL 10 mg/L (as nitrogen)) can cause methemoglobinemia ("blue baby syndrome") in infants under six months; Arsenic (EPA MCL 0.010 mg/L (10 ppb)) is linked to skin damage, circulatory problems and increased cancer risk; Copper (EPA action level 1.3 mg/L) causes stomach upset short-term and liver or kidney damage with long exposure.

Each of these tracks a different pathway into the tap. Total trihalomethanes are a surface-water signature: chlorine reacts with organic matter in rivers and reservoirs, so byproducts tend to run higher where systems chlorinate surface water. Arsenic is naturally occurring and tends to show up in groundwater, leaching from bedrock into aquifers rather than arriving from pollution. Nitrate follows fertilizer, manure and septic loading, so it is most often a concern for systems drawing shallow groundwater in farm regions. PFAS are tied to specific sites — industrial discharges, firefighting-foam use at airports and bases — rather than to geology, so contamination is local and can affect either source type. Lead is different again: it enters after treatment from service lines and household plumbing, which is why the inventory figures above matter more than plant-level results. Your utility's Consumer Confidence Report names your source.

The best water quality in Washington is found in Seattle with a score of 100/100 and a grade of A. This puts Seattle among the top-performing cities in the country for drinking water safety.

The most concerning water quality is in Vancouver scoring 74/100 with a grade of C. Residents may want to consider home water testing and filtration options.

The statewide average score is 89/100, which is 1 points above the national average of 88/100. Over half (50%) of Washington cities score above the national average, though some areas face challenges.