Water hardness in Tennessee
Tennessee has a median ambient water hardness of 78 mg/L, which is 4.6 grains per gallon and classes as moderately hard. That is the middle of 49,820 samples across 95 counties.
This is ambient water, not tap water. These figures come from samples taken from wells, streams and springs by USGS, EPA and state agencies. Municipal utilities treat, blend and sometimes soften water before it reaches a tap, so a city supply can be considerably softer than the ground beneath it. Treat this as a good guide for a private well and an approximate one for city water. Your utility's annual water quality report gives the real number for a municipal tap, and a test strip gives it for yours.
Every monitored county in Tennessee
Ranked hardest first. The middle 50% column shows how much the samples within a county vary, which matters more than the median where a county spans two geologies.
| County | mg/L | gpg | Class | Middle 50% | Samples |
|---|---|---|---|---|---|
| Greene County | 246 | 14.4 | Very hard | 215 to 264 | 769 |
| Washington County | 240 | 14 | Very hard | 97 to 264 | 840 |
| Hamblen County | 231 | 13.5 | Very hard | 210 to 254 | 36 |
| Sullivan County | 230 | 13.4 | Very hard | 113 to 262 | 934 |
| Marshall County | 210 | 12.3 | Very hard | 180 to 270 | 149 |
| Robertson County | 200 | 11.7 | Very hard | 175 to 220 | 251 |
| Williamson County | 200 | 11.7 | Very hard | 153 to 240 | 532 |
| Trousdale County | 199 | 11.6 | Very hard | 199 to 213 | 3 |
| Rutherford County | 193 | 11.3 | Very hard | 156 to 230 | 1,358 |
| Maury County | 180 | 10.5 | Hard | 144 to 215 | 462 |
| Grainger County | 172 | 10 | Hard | 120 to 227 | 80 |
| Wilson County | 171 | 10 | Hard | 90 to 230 | 486 |
| Hancock County | 168 | 9.8 | Hard | 135 to 195 | 329 |
| Union County | 164 | 9.6 | Hard | 148 to 209 | 81 |
| Lincoln County | 159 | 9.3 | Hard | 97 to 200 | 180 |
| McMinn County | 156 | 9.1 | Hard | 79 to 180 | 390 |
| Bradley County | 154 | 9 | Hard | 121 to 180 | 325 |
| Cannon County | 154 | 9 | Hard | 130 to 190 | 205 |
| Dickson County | 153 | 8.9 | Hard | 130 to 179 | 413 |
| Houston County | 150 | 8.8 | Hard | 121 to 170 | 68 |
| Lauderdale County | 150 | 8.8 | Hard | 66 to 280 | 350 |
| Montgomery County | 149 | 8.7 | Hard | 116 to 190 | 608 |
| Anderson County | 140 | 8.2 | Hard | 110 to 180 | 912 |
| Overton County | 140 | 8.2 | Hard | 105 to 172 | 356 |
| Putnam County | 137 | 8 | Hard | 80 to 161 | 546 |
| Davidson County | 135 | 7.9 | Hard | 75 to 220 | 1,595 |
| Claiborne County | 134 | 7.8 | Hard | 91 to 175 | 1,154 |
| Bedford County | 130 | 7.6 | Hard | 83 to 183 | 384 |
| Cheatham County | 130 | 7.6 | Hard | 98 to 160 | 555 |
| White County | 130 | 7.6 | Hard | 90 to 170 | 245 |
| Giles County | 124 | 7.2 | Hard | 110 to 147 | 280 |
| Hawkins County | 120 | 7 | Moderately hard | 98 to 155 | 593 |
| Lake County | 120 | 7 | Moderately hard | 99 to 226 | 61 |
| Meigs County | 120 | 7 | Moderately hard | 79 to 160 | 178 |
| Stewart County | 118 | 6.9 | Moderately hard | 100 to 140 | 207 |
| Warren County | 114 | 6.7 | Moderately hard | 85 to 160 | 361 |
| Sequatchie County | 110 | 6.4 | Moderately hard | 30 to 186 | 183 |
| Campbell County | 105 | 6.1 | Moderately hard | 60 to 162 | 397 |
| Macon County | 105 | 6.1 | Moderately hard | 75 to 120 | 72 |
| Hickman County | 100 | 5.8 | Moderately hard | 50 to 135 | 152 |
| Jefferson County | 100 | 5.8 | Moderately hard | 67 to 120 | 55 |
| Humphreys County | 99 | 5.8 | Moderately hard | 74 to 120 | 211 |
| Knox County | 99 | 5.8 | Moderately hard | 56 to 150 | 1,000 |
| Pickett County | 99 | 5.8 | Moderately hard | 86 to 112 | 386 |
| Sumner County | 97 | 5.7 | Moderately hard | 86 to 170 | 386 |
| Jackson County | 95 | 5.5 | Moderately hard | 84 to 116 | 304 |
| Clay County | 94 | 5.5 | Moderately hard | 87 to 103 | 529 |
| Roane County | 88 | 5.1 | Moderately hard | 24 to 130 | 1,052 |
| Smith County | 87 | 5.1 | Moderately hard | 79 to 110 | 696 |
| DeKalb County | 83 | 4.8 | Moderately hard | 71 to 150 | 2,085 |
| Franklin County | 83 | 4.8 | Moderately hard | 65 to 110 | 333 |
| Loudon County | 78 | 4.6 | Moderately hard | 67 to 117 | 505 |
| Bledsoe County | 76 | 4.4 | Moderately hard | 26 to 131 | 262 |
| Marion County | 75 | 4.4 | Moderately hard | 61 to 104 | 635 |
| Coffee County | 73 | 4.3 | Moderately hard | 29 to 150 | 406 |
| Rhea County | 68 | 4 | Moderately hard | 39 to 86 | 486 |
| Lawrence County | 65 | 3.8 | Moderately hard | 48 to 87 | 207 |
| Moore County | 64 | 3.7 | Moderately hard | 28 to 143 | 38 |
| Hamilton County | 63 | 3.7 | Moderately hard | 2 to 102 | 1,412 |
| Tipton County | 63 | 3.7 | Moderately hard | 32 to 191 | 456 |
| Grundy County | 58 | 3.4 | Soft | 20 to 112 | 178 |
| Hardin County | 48 | 2.8 | Soft | 20 to 64 | 370 |
| Johnson County | 47 | 2.7 | Soft | 22 to 70 | 522 |
| Wayne County | 46 | 2.7 | Soft | 36 to 71 | 145 |
| Shelby County | 45 | 2.6 | Soft | 18 to 77 | 5,568 |
| Crockett County | 43 | 2.5 | Soft | 20 to 53 | 104 |
| Fentress County | 41 | 2.4 | Soft | 14 to 119 | 359 |
| Perry County | 41 | 2.4 | Soft | 35 to 46 | 251 |
| Scott County | 39 | 2.3 | Soft | 12 to 80 | 1,485 |
| Sevier County | 39 | 2.3 | Soft | 7 to 57 | 228 |
| Van Buren County | 39 | 2.3 | Soft | 23 to 77 | 128 |
| Dyer County | 38 | 2.2 | Soft | 27 to 66 | 318 |
| Carter County | 37 | 2.2 | Soft | 20 to 82 | 501 |
| Cocke County | 32 | 1.9 | Soft | 19 to 78 | 628 |
| Decatur County | 31 | 1.8 | Soft | 22 to 88 | 98 |
| Lewis County | 31 | 1.8 | Soft | 25 to 46 | 108 |
| Cumberland County | 26 | 1.5 | Soft | 18 to 49 | 904 |
| Obion County | 26 | 1.5 | Soft | 20 to 69 | 567 |
| Henry County | 24 | 1.4 | Soft | 15 to 56 | 282 |
| McNairy County | 21 | 1.2 | Soft | 13 to 38 | 269 |
| Morgan County | 21 | 1.2 | Soft | 15 to 35 | 1,524 |
| Gibson County | 20 | 1.2 | Soft | 16 to 33 | 238 |
| Hardeman County | 20 | 1.2 | Soft | 13 to 26 | 329 |
| Polk County | 20 | 1.2 | Soft | 11 to 37 | 1,066 |
| Benton County | 19 | 1.1 | Soft | 15 to 37 | 174 |
| Monroe County | 19 | 1.1 | Soft | 7 to 140 | 251 |
| Haywood County | 18 | 1.1 | Soft | 0 to 32 | 376 |
| Unicoi County | 18 | 1.1 | Soft | 7 to 26 | 160 |
| Weakley County | 18 | 1.1 | Soft | 14 to 30 | 320 |
| Fayette County | 17 | 1 | Soft | 12 to 27 | 1,250 |
| Carroll County | 15 | 0.9 | Soft | 11 to 22 | 364 |
| Henderson County | 15 | 0.9 | Soft | 12 to 19 | 381 |
| Madison County | 14 | 0.8 | Soft | 0 to 20 | 848 |
| Chester County | 12 | 0.7 | Soft | 6 to 17 | 104 |
| Blount County | 9 | 0.5 | Soft | 5 to 100 | 898 |
Source: Water Quality Portal (USGS, EPA and state agencies), waterqualitydata.us, retrieved 2026-09-19. 2,904,346 samples across 3,110 counties.
What this means for a household in Tennessee
At 4.6 grains per gallon, a family of four would need a softener of about 16,000 grains to regenerate roughly weekly, using around 187 lb of salt a year. Size it for your own household.
92 of these counties include well samples, so the figures are a reasonable guide for private well water there. Municipal supplies in the same counties may be softer, because utilities often blend or treat.
Hardness follows geology rather than borders. Where a county sits on limestone or dolomite the water is hard; on granite, basalt or sandstone it is soft. That is why neighbouring counties in this table can differ by a factor of several.