Private wells
Texas well water: who's on a well and what to test for
People on private wells
2,241,600
Homes on wells
8.2%
Est. above arsenic limit
95,500
Every Texas county
Sorted by people on private wells. Arsenic and nitrate are modeled for typical wells in the county, not measured at yours; depth is the median of domestic well records.
| Harris County | 298,100 | 6% | 2.5% | 0.0 | 265 ft |
| Montgomery County | 106,300 | 17% | 1.7% | 0.0 | 220 ft |
| Brazoria County | 79,300 | 22% | 2.8% | 0.0 | 320 ft |
| Fort Bend County | 60,200 | 7% | 2.1% | 0.0 | 260 ft |
| Parker County | 50,300 | 34% | 2.7% | 0.6 | 222 ft |
| Tarrant County | 47,700 | 2% | 2.8% | 0.1 | 320 ft |
| Travis County | 36,400 | 3% | 1.6% | 0.6 | 300 ft |
| Williamson County | 32,700 | 5% | 1.3% | 0.5 | 380 ft |
| Ector County | 30,300 | 18% | 23.8% | 4.0 | 130 ft |
| El Paso County | 29,600 | 3% | 29.3% | 0.5 | 155 ft |
| Liberty County | 28,900 | 33% | 2.0% | 0.0 | 250 ft |
| Denton County | 27,500 | 3% | 1.6% | 0.1 | 400 ft |
| Wise County | 25,700 | 38% | 2.6% | 0.7 | 220 ft |
| Comal County | 25,500 | 16% | 1.2% | 0.3 | 410 ft |
| Lubbock County | 25,000 | 7% | 38.1% | 9.7 | 163 ft |
| Orange County | 24,900 | 29% | 1.0% | 0.0 | 390 ft |
| Bexar County | 24,400 | 1% | 2.0% | 0.8 | 400 ft |
| Midland County | 24,000 | 13% | 25.4% | 5.4 | 102 ft |
| Randall County | 24,000 | 16% | 2.9% | 3.0 | 310 ft |
| Galveston County | 23,600 | 6% | 3.7% | 0.0 | 223 ft |
| Hays County | 22,200 | 10% | 1.2% | 0.2 | 405 ft |
| Smith County | 21,000 | 9% | 1.6% | 0.1 | 220 ft |
| Johnson County | 20,100 | 12% | 2.9% | 0.1 | 300 ft |
| Walker County | 18,500 | 22% | 1.7% | 0.0 | 240 ft |
| Victoria County | 18,400 | 19% | 5.8% | 0.3 | 140 ft |
| Van Zandt County | 18,400 | 32% | 1.6% | 0.1 | 360 ft |
| Henderson County | 18,300 | 23% | 1.6% | 0.3 | 220 ft |
| Hardin County | 17,600 | 32% | 0.9% | 0.0 | 221 ft |
| Hidalgo County | 17,500 | 2% | 30.2% | 1.3 | 135 ft |
| Nueces County | 17,100 | 4% | 15.1% | 0.3 | 260 ft |
| Bowie County | 17,000 | 17% | 1.3% | 0.2 | 78 ft |
| Waller County | 16,900 | 34% | 2.4% | 0.1 | 240 ft |
| Guadalupe County | 16,700 | 11% | 3.0% | 1.0 | 230 ft |
| Dallas County | 16,600 | 1% | 6.9% | 0.7 | 60 ft |
| Jasper County | 16,600 | 50% | 1.0% | 0.0 | 170 ft |
| Val Verde County | 16,200 | 34% | 2.7% | 0.8 | 400 ft |
| Wharton County | 15,900 | 39% | 3.4% | 0.2 | 200 ft |
| Brazos County | 15,700 | 7% | 1.8% | 0.0 | 320 ft |
| Hood County | 15,700 | 24% | 1.9% | 0.2 | 344 ft |
| Washington County | 15,000 | 47% | 2.4% | 0.2 | 226 ft |
| Polk County | 14,900 | 32% | 1.6% | 0.0 | 195 ft |
| Jefferson County | 14,600 | 5% | 1.1% | 0.0 | 175 ft |
| Erath County | 14,400 | 36% | 2.5% | 0.4 | 356 ft |
| Bastrop County | 14,400 | 16% | 1.7% | 0.2 | 288 ft |
| Harrison County | 13,800 | 22% | 1.3% | 0.0 | 300 ft |
| Wilson County | 13,700 | 29% | 2.7% | 0.1 | 363 ft |
| Kerr County | 13,400 | 26% | 1.3% | 0.3 | 355 ft |
| Tom Green County | 13,300 | 11% | 2.8% | 3.6 | 100 ft |
| San Patricio County | 13,200 | 20% | 15.5% | 0.3 | 180 ft |
| San Jacinto County | 13,100 | 48% | 1.5% | 0.0 | 200 ft |
| Austin County | 12,600 | 44% | 2.3% | 0.2 | 200 ft |
| Burnet County | 12,500 | 26% | 1.8% | 0.4 | 280 ft |
| Kendall County | 12,400 | 29% | 1.4% | 0.2 | 300 ft |
| Gillespie County | 12,100 | 46% | 1.9% | 1.0 | 216 ft |
| Hunt County | 12,100 | 12% | 2.5% | 0.1 | 200 ft |
| Fayette County | 12,000 | 53% | 2.7% | 0.3 | 225 ft |
| Chambers County | 11,700 | 27% | 3.3% | 0.0 | 200 ft |
| Cameron County | 11,600 | 4% | 7.5% | 1.3 | 115 ft |
| Potter County | 11,600 | 8% | 4.9% | 2.6 | 290 ft |
| Kaufman County | 11,400 | 8% | 1.9% | 1.3 | 94 ft |
| Jim Wells County | 11,300 | 30% | 38.9% | 0.3 | 360 ft |
| Tyler County | 11,000 | 57% | 1.4% | 0.1 | 150 ft |
| Bandera County | 10,900 | 54% | 1.3% | 0.1 | 440 ft |
| Grimes County | 10,600 | 42% | 1.9% | 0.1 | 280 ft |
| Lavaca County | 10,500 | 56% | 3.8% | 0.3 | 170 ft |
| Rusk County | 10,400 | 22% | 1.4% | 0.0 | 340 ft |
| Medina County | 9,700 | 22% | 2.5% | 1.4 | 225 ft |
| Cherokee County | 9,300 | 20% | 1.5% | 0.1 | 220 ft |
| Gregg County | 9,100 | 7% | 1.5% | 0.0 | 408 ft |
| Montague County | 9,000 | 47% | 4.4% | 1.2 | 205 ft |
| Colorado County | 9,000 | 49% | 3.9% | 0.3 | 163 ft |
| Matagorda County | 9,000 | 27% | 3.0% | 0.0 | 375 ft |
| Upshur County | 8,900 | 23% | 1.6% | 0.0 | 402 ft |
| Grayson County | 8,900 | 8% | 1.8% | 0.1 | 300 ft |
| Cass County | 8,900 | 32% | 1.4% | 0.0 | 350 ft |
| Angelina County | 8,500 | 11% | 1.5% | 0.0 | 189 ft |
| Panola County | 8,500 | 40% | 1.6% | 0.0 | 225 ft |
| Atascosa County | 8,500 | 18% | 2.5% | 0.2 | 360 ft |
| Bell County | 8,400 | 2% | 1.6% | 0.4 | 182 ft |
| Nacogdoches County | 8,400 | 14% | 1.5% | 0.0 | 260 ft |
| Houston County | 8,300 | 46% | 1.9% | 0.1 | 280 ft |
| Wood County | 8,300 | 18% | 1.7% | 0.1 | 182 ft |
| Bee County | 8,300 | 36% | 37.7% | 0.6 | 180 ft |
| Anderson County | 8,100 | 20% | 1.5% | 0.1 | 160 ft |
| Aransas County | 7,900 | 30% | 8.5% | 0.0 | 170 ft |
| Gaines County | 7,900 | 33% | 60.8% | 7.3 | 192 ft |
| Shelby County | 7,400 | 32% | 1.8% | 0.0 | 240 ft |
| DeWitt County | 7,300 | 43% | 6.5% | 0.4 | 180 ft |
| Collin County | 7,200 | 1% | 2.3% | 0.2 | 67 ft |
| Newton County | 7,200 | 60% | 0.9% | 0.0 | 140 ft |
| Comanche County | 7,200 | 56% | 4.7% | 1.8 | 130 ft |
| Howard County | 7,000 | 23% | 12.0% | 7.8 | 90 ft |
| Burleson County | 7,000 | 40% | 2.3% | 0.0 | 300 ft |
| Cooke County | 6,900 | 18% | 1.7% | 0.1 | 390 ft |
| Caldwell County | 6,300 | 15% | 2.3% | 0.8 | 240 ft |
| Llano County | 6,100 | 32% | 4.0% | 1.3 | 140 ft |
| Ellis County | 5,900 | 3% | 2.7% | 0.2 | 340 ft |
| Gonzales County | 5,600 | 33% | 2.2% | 0.2 | 300 ft |
| Jackson County | 5,400 | 36% | 4.2% | 0.2 | 160 ft |
| McLennan County | 5,400 | 2% | 1.9% | 0.6 | 43 ft |
| Hockley County | 5,200 | 24% | 40.8% | 8.0 | 167 ft |
| Lee County | 5,200 | 34% | 1.6% | 0.0 | 304 ft |
| Blanco County | 5,200 | 48% | 1.4% | 0.3 | 300 ft |
| Leon County | 5,100 | 35% | 1.6% | 0.1 | 340 ft |
| Uvalde County | 5,000 | 25% | 2.3% | 1.0 | 208 ft |
| Milam County | 5,000 | 22% | 1.4% | 0.6 | 240 ft |
| Live Oak County | 4,900 | 53% | 21.5% | 0.8 | 220 ft |
| Karnes County | 4,700 | 24% | 9.9% | 0.4 | 233 ft |
| Sabine County | 4,700 | 46% | 1.3% | 0.0 | 135 ft |
| Goliad County | 4,500 | 66% | 13.9% | 0.3 | 200 ft |
| Madison County | 4,400 | 44% | 1.9% | 0.0 | 333 ft |
| Frio County | 4,400 | 20% | 2.9% | 0.6 | 304 ft |
| Robertson County | 4,400 | 29% | 1.6% | 0.1 | 360 ft |
| Bosque County | 4,300 | 27% | 1.4% | 0.1 | 240 ft |
| Limestone County | 4,200 | 22% | 1.8% | 0.1 | 285 ft |
| Falls County | 4,100 | 24% | 1.7% | 1.3 | 64 ft |
| Andrews County | 4,100 | 21% | 72.4% | 7.1 | 112 ft |
| Starr County | 4,100 | 8% | 45.9% | 1.3 | 250 ft |
| Hamilton County | 3,900 | 50% | 1.3% | 0.2 | 400 ft |
| Callahan County | 3,900 | 29% | 1.5% | 2.5 | 54 ft |
| Taylor County | 3,800 | 3% | 3.0% | 4.0 | 55 ft |
| Freestone County | 3,800 | 17% | 1.9% | 0.1 | 264 ft |
| Calhoun County | 3,800 | 23% | 6.3% | 0.1 | 225 ft |
| Scurry County | 3,700 | 25% | 15.2% | 3.8 | 220 ft |
| Deaf Smith County | 3,600 | 21% | 4.9% | 4.0 | 325 ft |
| Somervell County | 3,600 | 41% | 1.6% | 0.1 | 393 ft |
| San Augustine County | 3,500 | 47% | 1.4% | 0.0 | 191 ft |
| Palo Pinto County | 3,400 | 11% | 6.7% | 0.8 | 200 ft |
| Hale County | 3,400 | 12% | 6.2% | 3.3 | 305 ft |
| Trinity County | 3,400 | 27% | 2.1% | 0.0 | 243 ft |
| Brown County | 3,200 | 11% | 2.1% | 3.1 | 106 ft |
| Jack County | 3,100 | 45% | 9.3% | 1.5 | 200 ft |
| Clay County | 3,000 | 31% | 12.3% | 4.6 | 160 ft |
| Hill County | 3,000 | 9% | 2.2% | 0.2 | 280 ft |
| Eastland County | 3,000 | 19% | 4.0% | 2.7 | 90 ft |
| Coryell County | 2,900 | 5% | 1.3% | 0.1 | 400 ft |
| Fannin County | 2,800 | 9% | 2.1% | 0.7 | 70 ft |
| Titus County | 2,800 | 10% | 2.0% | 0.5 | 127 ft |
| Jones County | 2,600 | 17% | 8.1% | 9.2 | 52 ft |
| Brooks County | 2,600 | 35% | 16.4% | 0.1 | 400 ft |
| Brewster County | 2,600 | 34% | 6.4% | 1.4 | 243 ft |
| Wilbarger County | 2,500 | 20% | 4.3% | 14.5 | 38 ft |
| Parmer County | 2,500 | 28% | 14.9% | 3.3 | 398 ft |
| Lamb County | 2,400 | 19% | 21.6% | 7.6 | 215 ft |
| Mills County | 2,400 | 60% | 3.1% | 0.9 | 270 ft |
| Marion County | 2,400 | 27% | 1.5% | 0.0 | 340 ft |
| Morris County | 2,400 | 21% | 1.6% | 0.1 | 300 ft |
| Lampasas County | 2,400 | 14% | 1.8% | 0.7 | 284 ft |
| Rains County | 2,300 | 20% | 1.4% | 0.4 | 189 ft |
| Young County | 2,300 | 13% | 9.2% | 4.5 | 122 ft |
| Martin County | 2,200 | 42% | 35.7% | 10.9 | 98 ft |
| Gray County | 2,200 | 7% | 2.8% | 1.9 | 380 ft |
| Hutchinson County | 2,200 | 10% | 3.5% | 1.7 | 310 ft |
| Dawson County | 2,200 | 19% | 82.4% | 14.8 | 122 ft |
| Kleberg County | 2,200 | 7% | 14.9% | 0.0 | n/a |
| Refugio County | 2,200 | 34% | 6.9% | 0.0 | 240 ft |
| San Saba County | 2,200 | 35% | 4.2% | 1.5 | 240 ft |
| Hopkins County | 2,100 | 6% | 1.8% | 0.3 | 324 ft |
| Terry County | 2,000 | 17% | 60.5% | 13.2 | 142 ft |
| Castro County | 2,000 | 29% | 4.4% | 3.7 | 363 ft |
| Dimmit County | 2,000 | 23% | 3.7% | 0.2 | 360 ft |
| Mason County | 1,900 | 57% | 2.8% | 1.3 | 162 ft |
| Wheeler County | 1,800 | 37% | 2.9% | 4.8 | 135 ft |
| Kimble County | 1,700 | 53% | 1.9% | 0.9 | 220 ft |
| Rockwall County | 1,700 | 2% | 4.9% | 0.8 | n/a |
| Duval County | 1,700 | 20% | 36.1% | 0.4 | 340 ft |
| Bailey County | 1,700 | 28% | 17.2% | 8.0 | 225 ft |
| Lynn County | 1,700 | 28% | 31.6% | 19.1 | 131 ft |
| Real County | 1,700 | 69% | 1.4% | 0.3 | 240 ft |
| Camp County | 1,700 | 16% | 1.8% | 0.1 | 300 ft |
| Nolan County | 1,700 | 13% | 6.1% | 2.8 | 200 ft |
| Willacy County | 1,700 | 11% | 17.7% | 1.7 | n/a |
| Wichita County | 1,600 | 1% | 16.4% | 10.0 | 36 ft |
| Pecos County | 1,600 | 12% | 4.0% | 1.4 | 268 ft |
| Navarro County | 1,600 | 3% | 2.4% | 1.1 | 48 ft |
| Yoakum County | 1,500 | 19% | 52.0% | 9.4 | 170 ft |
| Swisher County | 1,300 | 21% | 3.0% | 4.4 | 210 ft |
| Jim Hogg County | 1,300 | 26% | 35.2% | 0.3 | 340 ft |
| Moore County | 1,300 | 6% | 4.4% | 2.3 | 400 ft |
| Ochiltree County | 1,200 | 13% | 3.5% | 2.3 | 400 ft |
| Carson County | 1,200 | 20% | 3.5% | 1.5 | 350 ft |
| Runnels County | 1,200 | 13% | 3.0% | 4.5 | 80 ft |
| Coke County | 1,200 | 47% | 2.9% | 2.4 | 150 ft |
| Floyd County | 1,100 | 22% | 13.0% | 2.0 | 320 ft |
| La Salle County | 1,100 | 16% | 2.8% | 0.1 | 295 ft |
| Donley County | 1,100 | 38% | 4.0% | 5.7 | 147 ft |
| Reeves County | 1,100 | 10% | 7.3% | 1.9 | 215 ft |
| Mitchell County | 1,100 | 16% | 10.9% | 4.3 | 120 ft |
| Jeff Davis County | 1,100 | 56% | 14.0% | 1.4 | 283 ft |
| Glasscock County | 1,100 | 94% | 4.6% | 3.4 | 200 ft |
| Maverick County | 1,100 | 2% | 3.5% | 0.7 | 69 ft |
| Dallam County | 1,000 | 14% | 11.5% | 2.7 | 400 ft |
| Knox County | 950 | 30% | 3.5% | 16.3 | 43 ft |
| Lamar County | 930 | 2% | 1.7% | 0.6 | 70 ft |
| Zavala County | 920 | 10% | 3.1% | 0.4 | 220 ft |
| Hemphill County | 910 | 26% | 2.8% | 1.4 | 232 ft |
| Irion County | 910 | 60% | 2.2% | 1.4 | 175 ft |
| Garza County | 880 | 27% | 11.9% | 5.5 | 100 ft |
| Franklin County | 880 | 10% | 2.2% | 0.8 | 190 ft |
| Haskell County | 870 | 18% | 5.4% | 11.5 | 53 ft |
| Hartley County | 850 | 19% | 8.1% | 1.9 | 340 ft |
| Hansford County | 810 | 16% | 4.8% | 3.0 | 400 ft |
| Sutton County | 810 | 30% | 2.4% | 0.7 | 336 ft |
| McCulloch County | 810 | 14% | 3.0% | 1.8 | 208 ft |
| Ward County | 770 | 7% | 11.6% | 2.3 | 130 ft |
| Upton County | 720 | 22% | 4.3% | 2.6 | 236 ft |
| Red River County | 720 | 7% | 1.8% | 0.3 | 85 ft |
| Crosby County | 720 | 18% | 15.2% | 4.0 | 300 ft |
| Schleicher County | 720 | 35% | 2.2% | 0.8 | 340 ft |
| Archer County | 610 | 7% | 15.8% | 5.5 | 80 ft |
| Menard County | 590 | 43% | 2.2% | 1.4 | 175 ft |
| Webb County | 580 | 0% | 9.3% | 0.1 | 360 ft |
| Lipscomb County | 570 | 22% | 2.9% | 2.0 | 280 ft |
| Sherman County | 560 | 22% | 4.3% | 2.7 | 429 ft |
| Fisher County | 540 | 13% | 7.6% | 7.8 | 116 ft |
| Armstrong County | 540 | 33% | 4.1% | 2.3 | 265 ft |
| Kinney County | 540 | 6% | 2.0% | 0.9 | 200 ft |
| Hardeman County | 530 | 15% | 3.0% | 8.6 | 92 ft |
| Dickens County | 520 | 30% | 2.7% | 2.9 | 101 ft |
| Presidio County | 480 | 8% | 20.2% | 1.6 | 263 ft |
| Edwards County | 460 | 51% | 1.7% | 0.5 | 360 ft |
| Baylor County | 440 | 18% | 6.3% | 9.7 | 30 ft |
| Briscoe County | 430 | 34% | 4.7% | 3.5 | 200 ft |
| Cochran County | 430 | 16% | 26.5% | 5.5 | 205 ft |
| Stonewall County | 420 | 40% | 4.3% | 4.5 | 60 ft |
| Crane County | 420 | 8% | 7.5% | 3.5 | 240 ft |
| Stephens County | 420 | 7% | 7.4% | 2.6 | 125 ft |
| Hudspeth County | 410 | 20% | 13.0% | 1.1 | 177 ft |
| Sterling County | 390 | 34% | 2.6% | 2.1 | 110 ft |
| Winkler County | 390 | 4% | 21.6% | 4.6 | 200 ft |
| Concho County | 380 | 21% | 2.1% | 2.6 | 110 ft |
| Crockett County | 380 | 17% | 2.4% | 0.8 | 360 ft |
| Reagan County | 370 | 13% | 3.3% | 1.6 | 280 ft |
| Borden County | 370 | 66% | 18.4% | 5.8 | 94 ft |
| Zapata County | 350 | 3% | 11.7% | 0.1 | 400 ft |
| Oldham County | 340 | 17% | 8.4% | 2.5 | 300 ft |
| Coleman County | 340 | 4% | 2.5% | 2.6 | 60 ft |
| Motley County | 300 | 33% | 2.9% | 6.1 | 92 ft |
| McMullen County | 300 | 43% | 2.2% | 0.3 | 210 ft |
| Roberts County | 300 | 36% | 2.9% | 0.8 | 385 ft |
| Collingsworth County | 260 | 11% | 3.2% | 8.8 | 100 ft |
| Kent County | 210 | 43% | 5.8% | 4.0 | 100 ft |
| Culberson County | 180 | 11% | 6.4% | 1.4 | 347 ft |
| Hall County | 170 | 8% | 3.4% | 7.0 | 100 ft |
| Cottle County | 140 | 10% | 2.9% | 4.4 | 138 ft |
| Foard County | 140 | 13% | 3.1% | 6.4 | 38 ft |
| Childress County | 140 | 3% | 3.0% | 7.4 | 110 ft |
| Delta County | 120 | 3% | 1.9% | 0.3 | n/a |
| Terrell County | 110 | 22% | 3.1% | 0.7 | n/a |
| Kenedy County | 100 | 25% | 9.3% | 0.0 | n/a |
| Shackelford County | 80 | 2% | 2.0% | 3.6 | 30 ft |
| Throckmorton County | 70 | 6% | 3.3% | 4.7 | 24 ft |
| King County | 50 | 21% | 2.5% | 3.7 | n/a |
| Loving County | 40 | 56% | 9.3% | 1.3 | 230 ft |
Shading: red is among the highest counties nationally, amber the middle, green the lower range. Click a column to sort.
Most well users above the arsenic limit
- Lubbock County: about 11,600 people
- Midland County: about 7,300 people
- Harris County: about 6,400 people
- Ector County: about 5,400 people
- Montgomery County: about 3,700 people
Highest modeled nitrate
- Lynn County: 19.1 mg/L average (limit 10)
- Knox County: 16.3 mg/L average (limit 10)
- Dawson County: 14.8 mg/L average (limit 10)
- Wilbarger County: 14.5 mg/L average (limit 10)
- Terry County: 13.2 mg/L average (limit 10)
Test first, then treat what the test finds
We may earn a commission from links below, at no cost to you. Picks follow the testing order, not who pays. How we make money.
1. Certified lab well test
Start here, every year
A mail-in kit analyzed by a certified lab measures bacteria, nitrate, arsenic, metals and more. Test strips cannot measure arsenic or uranium reliably.
2. Sediment pre-filter
Sand, silt or cloudy water
A 5-micron cartridge after the pressure tank catches sand, silt and rust before they reach fixtures or other filters. Cartridges are cheap and swap every few months.
3. Iron and sulfur filter
Orange stains or rotten-egg smell
Air-injection or oxidizing-media filters remove orange staining and rotten-egg smell. Size one from a lab result for iron, manganese and hydrogen sulfide.
4. UV disinfection system
Coliform bacteria in a test
Inactivates bacteria and viruses; usually for private wells or after boil notices.
5. Under-sink reverse osmosis
Arsenic, nitrate or uranium in a test
The most thorough option for drinking water: PFAS, lead, nitrate, arsenic and more. Look for NSF/ANSI 58.
6. Whole-house well filter
Several problems at once
Multi-stage sediment and carbon for every tap. Add UV if bacteria shows up, and choose stages from your lab results, not a guess.
Questions
Which Texas counties rely most on wells?+
By share of homes: Glasscock County (94%), Real County (69%), Borden County (66%), Goliad County (66%), Newton County (60%). By number of people: Harris County (298,100), Montgomery County (106,300), Brazoria County (79,300).
Is arsenic a problem in Texas wells?+
USGS estimates about 95,500 Texas well users have water above the 10 microgram per liter arsenic limit that applies to public systems, the largest numbers in Lubbock County, Midland County, Harris County. Arsenic has no taste or smell, so only a lab test finds it.
Do I have to test my well when I sell a house in Texas?+
We could not confirm a statewide rule for Texas. Check with your county health department. Buyers can still make a lab test a condition of the offer.
How often should I test my well?+
No federal law covers private wells. EPA's drinking water limits apply to public water systems, so testing and treating a private well is up to the owner. EPA and CDC recommend testing at least once a year for coliform bacteria, nitrate, pH and total dissolved solids, and testing for arsenic, uranium, radon and other local concerns based on where you live.
Well-user counts, arsenic and nitrate figures are each a modeled estimate built from national datasets, not a count of tested wells, and well depths summarize drilling records rather than every well. Your own well can be very different from the county average, which is why the only answer for your home is a lab test. Sources: EPA Office of Research and Development, Water Source 2020 (private well estimates by census block); CDC Environmental Public Health Tracking, Well Water Index (from USGS nitrate and arsenic models); USGS, county-level domestic well population with arsenic above 10 micrograms per liter (Ayotte and others, 2017); USGS Synthesized Domestic Well Database for the Conterminous United States (SynDWell-US), McCarthy and others, 2025 (depth, where a county has 30+ usable records).