Largest US Water Systems by Population Served
25 of 4,194 city reports shown, ranked by population served, from public EPA records (2024-12-31). It ranks the published record, not which water is safest.
New York City System ranks first in 2026
New York City System is first, at 8,271,000 served (population served). Los Angeles-City, Dept. of Water & Power (3,875,566 served), City of Houston (2,970,543 served), Chicago (2,721,308 served) and San Antonio Water System (2,643,729 served) follow. San Jose Water (1,039,920 served) and Atlanta (1,089,893 served) rank last.
All 25 ranked water systems
- 1New York City SystemNew York City, NYNEW YORK CITY SYSTEM · PWSID NY7003493 · Purity Score 74/100 · Confidence: not yet published8,271,000 served
- 2Los Angeles-City, Dept. of Water & PowerLos Angeles, CALOS ANGELES-CITY, DEPT. OF WATER & POWER · PWSID CA1910067 · Purity Score 90/100 · Confidence: not yet published3,875,566 served
- 3City of HoustonHouston, TXCITY OF HOUSTON · PWSID TX1010013 · Purity Score 87/100 · Confidence: not yet published2,970,543 served
- 4ChicagoChicago, ILCHICAGO · PWSID IL0316000 · Purity Score 91/100 · Confidence: not yet published2,721,308 served
- 5San Antonio Water SystemSan Antonio, TXSAN ANTONIO WATER SYSTEM · PWSID TX0150018 · Purity Score 95/100 · Confidence: not yet published2,643,729 served
- 6Mdwasa - Main SystemMiami, FLMDWASA - MAIN SYSTEM · PWSID FL4130871 · Purity Score 54/100 · Confidence: not yet published2,377,460 served
- 7Washington Suburban Sanitary CommissionMontgomery and Prince George's (WSSC area), MDWASHINGTON SUBURBAN SANITARY COMMISSION · PWSID MD0150005 · Purity Score 100/100 · Confidence: not yet published1,900,000 served
- 8Phoenix City ofPhoenix, AZPHOENIX CITY OF · PWSID AZ0407025 · Purity Score 90/100 · Confidence: not yet published1,695,000 served
- 9City of BaltimoreBaltimore, MDCITY OF BALTIMORE · PWSID MD0300002 · Purity Score 93/100 · Confidence: not yet published1,600,000 served
- 10Philadelphia Water DepartmentPhiladelphia, PAPHILADELPHIA WATER DEPARTMENT · PWSID PA1510001 · Purity Score 61/100 · Confidence: not yet published1,600,000 served
- 11Las Vegas Valley Water DistrictLas Vegas, NVLAS VEGAS VALLEY WATER DISTRICT · PWSID NV0000090 · Purity Score 85/100 · Confidence: not yet published1,539,277 served
- 12East Bay MUDOakland, CAEAST BAY MUD · PWSID CA0110005 · Purity Score 100/100 · Confidence: not yet published1,468,000 served
- 13San Diego, City ofSan Diego, CASAN DIEGO, CITY OF · PWSID CA3710020 · Purity Score 100/100 · Confidence: not yet published1,408,937 served
- 14Dallas Water UtilityDallas, TXDALLAS WATER UTILITY · PWSID TX0570004 · Purity Score 70/100 · Confidence: not yet published1,356,479 served
- 15Columbus Public Water SystemColumbus, OHCOLUMBUS PUBLIC WATER SYSTEM · PWSID OH2504412 · Purity Score 70/100 · Confidence: not yet published1,309,468 served
- 16Cleveland Public Water SystemCleveland, OHCLEVELAND PUBLIC WATER SYSTEM · PWSID OH1801212 · Purity Score 97/100 · Confidence: not yet published1,308,955 served
- 17Denver Water BoardDenver, CODENVER WATER BOARD · PWSID CO0116001 · Purity Score 93/100 · Confidence: not yet published1,287,000 served
- 18Charlotte WaterCharlotte, NCCHARLOTTE WATER · PWSID NC0160010 · Purity Score 93/100 · Confidence: not yet published1,206,285 served
- 19Seattle Public UtilitiesSeattle, WASEATTLE PUBLIC UTILITIES · PWSID WA5377050 · Purity Score 94/100 · Confidence: not yet published1,161,961 served
- 20Fairfax County Water AuthorityFairfax County, VAFAIRFAX COUNTY WATER AUTHORITY · PWSID VA6059501 · Purity Score 59/100 · Confidence: not yet published1,121,613 served
- 21City of Austin Water & WastewaterAustin, TXCITY OF AUSTIN WATER & WASTEWATER · PWSID TX2270001 · Purity Score 73/100 · Confidence: not yet published1,115,323 served
- 22Mo American St Louis St Charles CountiesFlorissant, MOMO AMERICAN ST LOUIS ST CHARLES COUNTIES · PWSID MO6010716 · Purity Score 100/100 · Confidence: not yet published1,111,000 served
- 23Suffolk County Water AuthoritySuffolk County, NYSUFFOLK COUNTY WATER AUTHORITY · PWSID NY5110526 · Purity Score 55/100 · Confidence: not yet published1,100,000 served
- 24AtlantaAtlanta, GAATLANTA · PWSID GA1210001 · Purity Score 88/100 · Confidence: not yet published1,089,893 served
- 25San Jose WaterCampbell, CASAN JOSE WATER · PWSID CA4310011 · Purity Score 66/100 · Confidence: not yet published1,039,920 served
The top 25 of 4,194 city reports are listed. Only cities with a computed Purity Score and a resolved serving system are eligible; all others are excluded.
How this snapshot is built
- How this snapshot is built
Public water systems ranked by the population they serve, from the EPA SDWIS record. Included to orient readers to the systems whose records affect the most people.
- Reading the order
Population figures are as reported to EPA and can lag real service-area changes. Size is not a quality signal.
- Exclusions
The top 25 of 4,194 city reports are shown. Only cities with a computed Purity Score and a resolved serving system are eligible; all others are excluded.
Comparable does not mean complete.
This ranking compares water systems on one measure. It never replaces a full system report, a city-resolution check, or a certified household test, and missing monitoring is excluded, never scored as favourable.