Water systems with the most service lines of unknown material
An unknown line hasn't been ruled out as lead. City of Houston reported the most, 427,111. Homes on these systems are likely to receive annual notices until their lines are identified. What "unknown" means.
| Rank / water system | Lead | Galv. | Unknown | % lead |
|---|---|---|---|---|
| 1City of HoustonHarris County, TX | 0 | 0 | 427,111 | 0% |
| 2Philadelphia Water DepartmentPhiladelphia County, PA | 16,805 | 1,777 | 351,513 | 3.5% |
| 3San Antonio Water SystemBexar County, TX | 0 | 43 | 346,335 | <0.1% |
| 4City of BaltimoreBaltimore City County, MD | 47 | 385 | 335,694 | <0.1% |
| 5Mdwasa - Main SystemMiami, FL | 0 | 0 | 289,930 | 0% |
| 6Dallas Water UtilityDallas County, TX | 0 | 6 | 258,104 | <0.1% |
| 7City of PhoenixPhoenix, AZ | 0 | 506 | 227,517 | 0.1% |
| 8PA Amer Water Co-PittsburghAllegheny County, PA | 4,290 | 1,780 | 207,101 | 2.6% |
| 9Mo American St Louis St Charles CountiesSt. Charles County, MO | 9,422 | 1,247 | 191,341 | 2.7% |
| 10MetropolitanoBayamon, PR | 0 | 3 | 190,837 | <0.1% |
| 11Albuquerque Water SystemAlbuquerque, NM | 0 | 20 | 170,705 | <0.1% |
| 12Memphis Light, Gas, & WaterMemphis, TN | 17,022 | 532 | 164,591 | 5.7% |
| 13Dekalb CountyDekalb County, GA | 0 | 0 | 155,835 | 0% |
| 14City of TucsonTucson, AZ | 0 | 341 | 140,797 | 0.1% |
| 15El Paso Water UtilitiesEl Paso County, TX | 0 | 9 | 134,633 | <0.1% |
| 16TulsaTulsa County, OK | 0 | 0 | 128,216 | 0% |
| 17New York City SystemNew York, NY | 120,931 | 3,266 | 124,917 | 15% |
| 18New Orleans Carrollton Water WorksOrleans Parish County, LA | 13,927 | 49 | 107,622 | 11% |
| 19North Las Vegas UtilitiesNorth Las Vegas, NV | 0 | 4 | 106,375 | <0.1% |
| 20E Jefferson WW District 1Jefferson Parish County, LA | 0 | 0 | 94,340 | 0% |
| 21City of Shreveport Water SystemCaddo Parish County, LA | 1,799 | 0 | 85,680 | 1.9% |
| 22Wvawc-Kanawha Valley DistCharleston, WV | 0 | 162 | 85,540 | 0.2% |
| 23City Utilities of SpringfieldSpringfield, MO | 1 | 16 | 84,955 | <0.1% |
| 24NJ American Water - RaritanElizabeth City- 2004, NJ | 429 | 5,590 | 76,716 | 2.7% |
| 25Metro Water ServicesNashville, TN | 2,818 | 21,855 | 76,180 | 11% |
| 26NJ American Water - Coastal NorthAberdeen Twp, NJ | 192 | 2,653 | 74,724 | 1.8% |
| 27OcwaSyracuse, NY | 400 | 3,495 | 72,099 | 3.3% |
| 28York Water CoYork County, PA | 9 | 111 | 71,283 | 0.2% |
| 29Kentucky-American Water CoFayette County, KY | 28 | 39 | 69,237 | <0.1% |
| 30City of Fort LauderdaleFt Lauderdale, FL | 2 | 20 | 69,050 | <0.1% |
| 31City of RichmondRichmond City, VA | 1,956 | 28 | 67,626 | 2.4% |
| 32Evansville Water UtilityEvansville, IN | 1 | 50 | 67,204 | <0.1% |
| 33City of GreensboroGreensboro, NC | 0 | 17 | 67,123 | <0.1% |
| 34Columbus Public Water SystemFranklin County, OH | 25,155 | 8,093 | 65,266 | 12% |
| 35Charleston Water System (Sc1010001)Charleston, SC | 6,504 | 2 | 65,064 | 4.8% |
| 36St Louis City PWSSt. Louis, MO | 9,990 | 525 | 64,378 | 9.9% |
| 37Pinellas County UtilitiesClearwater, FL | 0 | 6,472 | 63,789 | 5.6% |
| 38Aquarion-Eastern Fairfield CountyBeacon Falls, CT | 3,948 | 323 | 63,008 | 3.9% |
| 39Manatee County Utilities DeptBradenton, FL | 0 | 0 | 62,778 | 0% |
| 40Gru - Murphree WTPGainesville, FL | 0 | 441 | 62,471 | 0.4% |
| 41Louisville Water CompanyJefferson County, KY | 483 | 2,064 | 59,521 | 0.8% |
| 42W Jefferson WW District 2Jefferson Parish County, LA | 0 | 0 | 58,766 | 0% |
| 43Washington Suburban Sanitary CommissionMontgomery County, MD | 8 | 1,277 | 57,121 | 0.2% |
| 44Henrico County Water SystemHenrico County, VA | 2 | 3 | 57,120 | <0.1% |
| 45Cleveland Public Water SystemCuyahoga County, OH | 144,193 | 528 | 56,954 | 33% |
| 46City of CocoaCocoa, FL | 0 | 29 | 55,320 | <0.1% |
| 47City of DurhamDurham, NC | 0 | 37 | 54,372 | <0.1% |
| 48CWS - BakersfieldKern County, CA | 0 | 0 | 52,060 | 0% |
| 49Veolia Water IdahoAda County, ID | 0 | 0 | 51,992 | 0% |
| 50PA Amer Water Co Lake ScrantonLackawanna County, PA | 271 | 657 | 49,696 | 1.6% |
| 51NJ American Water - WesternAudubon Boro, NJ | 85 | 1,459 | 49,216 | 1.5% |
| 52Grand Strand W&sa/Bull CreekConway, SC | 0 | 0 | 47,216 | 0% |
| 53Des Moines Water WorksDes Moines, IA | 8,114 | 10 | 45,950 | 9.0% |
| 54Pcud-Pasco County Regional PWSNew Port Richey, FL | 0 | 107 | 44,613 | <0.1% |
| 55AtlantaAtlanta, GA | 0 | 0 | 43,429 | 0% |
| 56Tennessee American WaterChattanooga, TN | 2,368 | 0 | 43,208 | 2.6% |
| 57City of Chesapeake - Northwest River SysChesapeake City, VA | 0 | 9 | 42,895 | <0.1% |
| 58City of LancasterLancaster County, PA | 474 | 0 | 42,841 | 1.0% |
| 59Amarillo Municipal Water SystemPotter County, TX | 0 | 252 | 42,657 | 0.3% |
| 60City of AshevilleAsheville, NC | 2 | 219 | 42,588 | 0.3% |
| 61City of Beaumont Water Utility DeptJefferson County, TX | 1 | 102 | 41,727 | 0.2% |
| 62City of WichitaWichita, KS | 16 | 6,015 | 40,164 | 3.6% |
| 63Citizens Water - IndianapolisIndianapolis, IN | 56,766 | 195 | 39,935 | 15% |
| 64Jea Major GridJacksonville, FL | 0 | 8,365 | 39,556 | 1.9% |
| 65ChicagoCook County, IL | 350,531 | 10,326 | 39,427 | 74% |
| 66Aqua PA Main SystemMontgomery County, PA | 55 | 4,595 | 39,217 | 1.5% |
| 67City of DetroitDetroit, MI | 80,595 | 120 | 39,073 | 32% |
| 68Chester Water AuthorityDelaware County, PA | 148 | 1 | 38,696 | 0.3% |
| 69Gwa Northern Water SystemAdacao, GU | 0 | 0 | 38,633 | 0% |
| 70City of LaredoWebb County, TX | 0 | 0 | 37,615 | 0% |
| 71Central Alabama WaterBirmingham, AL | 12,350 | 18 | 36,839 | 5.3% |
| 72Indiana American Water - NorthwestGary, IN | 10,833 | 183 | 36,484 | 12% |
| 73City of VallejoVallejo, CA | 0 | 0 | 36,385 | 0% |
| 74Buffalo Water AuthorityBuffalo, NY | 34,208 | 110 | 35,839 | 45% |
| 75Veolia Water Delaware, INCNew Castle, DE | 0 | 78 | 35,490 | 0.2% |
| 76Wvawc - Huntington DistHuntington, WV | 845 | 390 | 35,182 | 2.8% |
| 77City of MissionHidalgo County, TX | 1 | 1 | 34,548 | <0.1% |
| 78IL American-East St LouisEast St Louis, IL | 749 | 351 | 34,431 | 1.5% |
| 79City of PortsmouthPortsmouth City, VA | 30 | 0 | 34,359 | <0.1% |
| 80Baton Rouge Water CompanyEast Baton Rouge Parish County, LA | 0 | 1,007 | 34,147 | 0.4% |
| 81Clearwater Water SystemClearwater, FL | 0 | 0 | 34,094 | 0% |
| 82Denver Water BoardDenver County, CO | 15,826 | 848 | 34,057 | 5.4% |
| 83Mvwa - Mohawk Valley Water AuthorityDeerfield, NY | 6,445 | 19 | 33,583 | 15% |
| 84City of ToledoLucas County, OH | 3,053 | 6,374 | 33,513 | 8.1% |
| 85City of TallahasseeTallahassee, FL | 0 | 349 | 32,992 | 0.4% |
| 86PA American Water Co WestCumberland County, PA | 39 | 1,712 | 32,832 | 4.0% |
| 87Oklahoma CityOklahoma County, OK | 173 | 6 | 32,667 | <0.1% |
| 88Schriever Water Treatment Service AreaTerrebonne Parish County, LA | 0 | 0 | 32,609 | 0% |
| 89California Water Service Co. - DominguezLos Angeles County, CA | 0 | 0 | 31,869 | 0% |
| 90Salt Lake City Water SystemSalt Lake County, UT | 120 | 102 | 31,866 | 0.3% |
| 91City of PasadenaHarris County, TX | 0 | 0 | 31,648 | 0% |
| 92Fayetteville Public Works CommFayetteville, NC | 0 | 247 | 31,568 | 0.2% |
| 93Town of Hempstead Water DepartmentHempstead, NY | 20 | 14 | 30,533 | <0.1% |
| 94PA American NorristownMontgomery County, PA | 43 | 374 | 30,340 | 1.2% |
| 95LivoniaLivonia, MI | 134 | 31 | 29,973 | 0.4% |
| 96City of BethlehemNorthampton County, PA | 0 | 777 | 29,933 | 2.1% |
| 97Artesian Water CompanyBear, DE | 148 | 374 | 29,413 | 0.6% |
| 98Paw CeasetownLuzerne County, PA | 127 | 370 | 29,346 | 1.6% |
| 99Ocud/Eastern Water System (2 WP)Orlando, FL | 0 | 0 | 29,009 | 0% |
| 100City of HialeahHialeah, FL | 0 | 0 | 28,882 | 0% |
Source: EPA SDWIS service line inventory, 2026 Q3.
Cite this list
Lead Pipe Map, "Water systems with the most service lines of unknown material," November 1, 2026, https://leadpipemap.com/rankings/most-unknown-service-lines/. Data: EPA SDWIS service line inventory, 2026 Q3.
Journalists and researchers are welcome to use these figures with a link back.