We analyzed tap water quality data for hundreds of cities in Washington to identify the 25 with the most contaminants exceeding health guidelines. This ranking is based on 2026 data from the EPA and EWG databases.
While all public water systems must meet EPA legal limits, many health experts — including the Environmental Working Group — argue that these legal limits are outdated and don't reflect current scientific understanding of safe exposure levels. The cities below have the widest gap between what's in their water and what's considered safe by modern health standards.
Rankings at a Glance
West Richland, Washington
West Richland has 20 contaminants exceeding EWG health guidelines out of 45 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full West Richland water report →Kennewick, Washington
Kennewick has 19 contaminants exceeding EWG health guidelines out of 34 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Kennewick water report →Richland, Washington
Richland has 18 contaminants exceeding EWG health guidelines out of 31 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Richland water report →Sammamish, Washington
Sammamish has 18 contaminants exceeding EWG health guidelines out of 31 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Sammamish water report →Federal Way, Washington
Federal Way has 17 contaminants exceeding EWG health guidelines out of 30 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Federal Way water report →Po Box 70, Washington
Po Box 70 has 17 contaminants exceeding EWG health guidelines out of 27 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Po Box 70 water report →Issaquah, Washington
Issaquah has 16 contaminants exceeding EWG health guidelines out of 30 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Issaquah water report →Kent, Washington
Kent has 15 contaminants exceeding EWG health guidelines out of 30 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Kent water report →Port Orchard, Washington
Port Orchard has 15 contaminants exceeding EWG health guidelines out of 28 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Port Orchard water report →Grandview, Washington
Grandview has 15 contaminants exceeding EWG health guidelines out of 24 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Grandview water report →Deer Park, Washington
Deer Park has 15 contaminants exceeding EWG health guidelines out of 24 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Deer Park water report →Olympia, Washington
Olympia has 15 contaminants exceeding EWG health guidelines out of 23 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Olympia water report →Centralia, Washington
Centralia has 15 contaminants exceeding EWG health guidelines out of 23 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Centralia water report →Stanwood, Washington
Stanwood has 15 contaminants exceeding EWG health guidelines out of 21 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Stanwood water report →Snohomish, Washington
Snohomish has 14 contaminants exceeding EWG health guidelines out of 27 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Snohomish water report →Vancouver, Washington
Vancouver has 14 contaminants exceeding EWG health guidelines out of 25 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Vancouver water report →Arlington, Washington
Arlington has 14 contaminants exceeding EWG health guidelines out of 24 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Arlington water report →Yakima, Washington
Yakima has 14 contaminants exceeding EWG health guidelines out of 23 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Yakima water report →Redmond, Washington
Redmond has 14 contaminants exceeding EWG health guidelines out of 22 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Redmond water report →Roy, Washington
Roy has 14 contaminants exceeding EWG health guidelines out of 20 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Roy water report →Joint Base Lewis-mcchord, Washington
Joint Base Lewis-mcchord has 13 contaminants exceeding EWG health guidelines out of 27 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Joint Base Lewis-mcchord water report →Moses Lake, Washington
Moses Lake has 13 contaminants exceeding EWG health guidelines out of 27 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Moses Lake water report →Spokane, Washington
Spokane has 13 contaminants exceeding EWG health guidelines out of 26 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Spokane water report →Puyallup, Washington
Puyallup has 13 contaminants exceeding EWG health guidelines out of 25 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Puyallup water report →Buckley, Washington
Buckley has 13 contaminants exceeding EWG health guidelines out of 24 detected — significantly above the national average. Multiple known carcinogens were found at levels of concern.
See full Buckley water report →What We Found: Key Patterns
The most frequently detected contaminants exceeding health guidelines across these cities are Bromodichloromethane, Total trihalomethanes (TTHMs), Dibromochloromethane. These appear repeatedly across different water systems and regions.
Water quality varies significantly even within the same state, driven by local geology, agricultural activity, and industrial proximity.
Across all ranked cities, 379 contaminant readings exceed EWG health guidelines, but only 11 exceed EPA legal limits. This gap of 368 highlights how legal standards may not fully protect public health — EPA limits haven't been updated for many contaminants in decades.
Full Rankings Table
| Rank | City | State | Detected | Above Guidelines | Above Legal | People Served |
|---|---|---|---|---|---|---|
| 1 | West Richland | WA | 45 | 20 | 1 | 17,410 |
| 2 | Kennewick | WA | 34 | 19 | 1 | 89,224 |
| 3 | Richland | WA | 31 | 18 | 1 | 94,463 |
| 4 | Sammamish | WA | 31 | 18 | 1 | 65,598 |
| 5 | Federal Way | WA | 30 | 17 | 0 | 116,906 |
| 6 | Po Box 70 | WA | 27 | 17 | 1 | 5,305 |
| 7 | Issaquah | WA | 30 | 16 | 2 | 39,578 |
| 8 | Kent | WA | 30 | 15 | 0 | 157,101 |
| 9 | Port Orchard | WA | 28 | 15 | 0 | 28,721 |
| 10 | Grandview | WA | 24 | 15 | 0 | 11,010 |
| 11 | Deer Park | WA | 24 | 15 | 0 | 0 |
| 12 | Olympia | WA | 23 | 15 | 0 | 113,584 |
| 13 | Centralia | WA | 23 | 15 | 0 | 28,164 |
| 14 | Stanwood | WA | 21 | 15 | 0 | 13,785 |
| 15 | Snohomish | WA | 27 | 14 | 0 | 22,932 |
| 16 | Vancouver | WA | 25 | 14 | 2 | 373,047 |
| 17 | Arlington | WA | 24 | 14 | 0 | 19,690 |
| 18 | Yakima | WA | 23 | 14 | 0 | 110,598 |
| 19 | Redmond | WA | 22 | 14 | 0 | 123,565 |
| 20 | Roy | WA | 20 | 14 | 1 | 1,214 |
| 21 | Joint Base Lewis-mcchord | WA | 27 | 13 | 1 | 58,497 |
| 22 | Moses Lake | WA | 27 | 13 | 0 | 32,428 |
| 23 | Spokane | WA | 26 | 13 | 0 | 343,167 |
| 24 | Puyallup | WA | 25 | 13 | 0 | 36,906 |
| 25 | Buckley | WA | 24 | 13 | 0 | 38,307 |
Frequently Asked Questions
What city has the worst tap water in Washington?
Based on 2026 data, West Richland, WA has the most contaminants exceeding EWG health guidelines among the cities we analyzed.
How are cities ranked in this report?
Cities are ranked by the number of contaminants exceeding EWG health guidelines. These guidelines are typically stricter than EPA legal limits and reflect current scientific research on safe exposure levels.
Is my tap water safe if my city isn't on this list?
Not necessarily. Even cities not on this list may have contaminants of concern. We recommend checking your specific water quality using our free water scan tool.
What's the best water filter for contaminated water?
A reverse osmosis (RO) system is the most effective for removing the widest range of contaminants. For whole-home protection, a combination of RO for drinking water and a whole-home filter for showers and baths is recommended.
Related Reports
Data sources: Environmental Working Group (EWG) Tap Water Database, U.S. EPA Safe Drinking Water Information System (SDWIS)
Last updated: April 2026
Methodology: Contaminant levels are compared against both EPA legal limits (Maximum Contaminant Levels) and EWG health guidelines, which are often stricter and based on the latest scientific research.
