The 50 largest US water systems: what EPA testing found
Ranked by people served (EPA SDWIS). PFAS and lithium come from EPA’s UCMR 5 testing (2023–2025, final data released August 2026); violations are health-based violations since 2016. Checked 16 Oct 2026.
| # | System | People served | PFOA/PFOS above EPA limit | PFAS found | Violations since 2016 |
|---|---|---|---|---|---|
| 1 | New York CityNew York City water supply system, NY | 8,271,000 | No | 0 | 1 |
| 2 | Los AngelesLos Angeles Department of Water and Power, CA | 3,875,566 | No | 0 | 1 |
| 3 | HoustonCity of Houston, TX | 2,970,543 | No | 4 | 1 |
| 4 | ChicagoCity of Chicago, IL | 2,721,308 | No | 0 | 0 |
| 5 | San AntonioSan Antonio Water System, TX | 2,643,729 | No | 3 | 0 |
| 6 | Greater Boston (wholesale supplier)Massachusetts Water Resources Authority (MWRA), MA | 2,580,000 | no UCMR 5 data | – | 0 |
| 7 | Miami-Dade CountyMiami-Dade Water and Sewer (main system), FL | 2,377,460 | Yes | 11 | 0 |
| 8 | Montgomery and Prince George’s countiesWSSC Water (Washington Suburban Sanitary Commission), MD | 1,900,000 | No | 2 | 0 |
| 9 | PhoenixCity of Phoenix, AZ | 1,695,000 | No | 2 | 1 |
| 10 | BaltimoreCity of Baltimore, MD | 1,600,000 | No | 1 | 3 |
| 11 | PhiladelphiaPhiladelphia Water Department, PA | 1,600,000 | Yes | 8 | 0 |
| 12 | Las VegasLas Vegas Valley Water District, NV | 1,539,277 | No | 2 | 0 |
| 13 | Oakland and the East BayEast Bay Municipal Utility District (EBMUD), CA | 1,468,000 | No | 2 | 0 |
| 14 | San DiegoCity of San Diego, CA | 1,408,937 | No | 0 | 0 |
| 15 | DallasDallas Water Utilities, TX | 1,356,479 | No | 8 | 0 |
| 16 | ColumbusCity of Columbus, OH | 1,309,468 | No | 6 | 0 |
| 17 | ClevelandCleveland Water, OH | 1,308,955 | No | 0 | 0 |
| 18 | DenverDenver Water, CO | 1,287,000 | No | 0 | 0 |
| 19 | CharlotteCharlotte Water, NC | 1,206,285 | No | 2 | 0 |
| 20 | SeattleSeattle Public Utilities, WA | 1,161,961 | No | 0 | 0 |
| 21 | Fairfax CountyFairfax Water (Fairfax County Water Authority), VA | 1,121,613 | Yes | 8 | 0 |
| 22 | AustinAustin Water, TX | 1,115,323 | No | 6 | 5 |
| 23 | St. Louis CountyMissouri American Water (St. Louis and St. Charles counties), MO | 1,111,000 | No | 1 | 0 |
| 24 | Suffolk County, Long IslandSuffolk County Water Authority, NY | 1,100,000 | Yes | 10 | 2 |
| 25 | AtlantaCity of Atlanta, GA | 1,089,893 | No | 4 | 5 |
| 26 | San Juan metro areaPRASA Metropolitano system, PR | 1,084,637 | Yes | 8 | 82 |
| 27 | San JoseSan Jose Water, CA | 1,039,920 | No | 2 | 1 |
| 28 | Gwinnett CountyGwinnett County Department of Water Resources, GA | 975,000 | No | 0 | 0 |
| 29 | Fort WorthCity of Fort Worth, TX | 955,900 | Yes | 7 | 1 |
| 30 | IndianapolisCitizens Water, IN | 880,345 | No | 4 | 0 |
| 31 | San FranciscoSan Francisco Public Utilities Commission (city distribution), CA | 848,019 | No | 0 | 0 |
| 32 | JacksonvilleJEA (major grid), FL | 826,664 | No | 2 | 0 |
| 33 | Philadelphia suburbsAqua Pennsylvania (main system), PA | 822,600 | Yes | 9 | 2 |
| 34 | LouisvilleLouisville Water Company, KY | 806,997 | No | 4 | 0 |
| 35 | CincinnatiGreater Cincinnati Water Works, OH | 800,000 | Yes | 3 | 0 |
| 36 | Bergen and Hudson countiesVeolia Water New Jersey (Hackensack system), NJ | 792,713 | Yes | 8 | 1 |
| 37 | NashvilleMetro Water Services, TN | 789,969 | No | 0 | 0 |
| 38 | El PasoEl Paso Water, TX | 747,168 | Yes | 6 | 0 |
| 39 | DeKalb CountyDeKalb County, GA | 743,000 | No | 0 | 0 |
| 40 | TampaCity of Tampa Water Department, FL | 733,886 | Yes | 8 | 0 |
| 41 | TucsonTucson Water, AZ | 732,906 | No | 1 | 0 |
| 42 | Cobb CountyCobb County Water System, GA | 695,000 | No | 3 | 0 |
| 43 | Pittsburgh areaPennsylvania American Water (Pittsburgh), PA | 686,000 | No | 0 | 1 |
| 44 | BostonBoston Water and Sewer Commission, MA | 675,647 | No | 0 | 1 |
| 45 | Palm Beach CountyPalm Beach County Water Utilities, FL | 671,114 | Yes | 9 | 1 |
| 46 | LexingtonKentucky American Water, KY | 669,042 | No | 5 | 0 |
| 47 | PortlandPortland Water Bureau, OR | 666,200 | No | 0 | 1 |
| 48 | OmahaMetropolitan Utilities District, NE | 660,000 | No | 0 | 0 |
| 49 | Moreno Valley, Hemet and PerrisEastern Municipal Water District, CA | 659,923 | No | 0 | 0 |
| 50 | MemphisMemphis Light, Gas and Water, TN | 659,500 | No | 0 | 0 |