Measured, not modelled
Measured well-water hardness for Ohio, county by county: the median of laboratory hardness samples taken at real water wells, in grains per gallon and mg/L as CaCO3, with the number of wells behind every figure.
Most published hardness-by-county tables are estimates from municipal tap water. The figures below are different: they are medians of laboratory samples taken at water wells, from the public record, and every row says how many wells stand behind it. The same table qualifies every lead Hard Water Feed sells, so this page is also how you check our arithmetic — the full method is on the methodology page.
Ratings below use the Water Quality Association scale, in grains per gallon (gpg); 1 gpg is 17.118 mg/L as CaCO3.
| Rating | Range |
|---|---|
| soft | 0 – 1 gpg |
| slightly hard | 1 – 3.5 gpg |
| moderately hard | 3.5 – 7 gpg |
| hard | 7 – 10.5 gpg |
| very hard | over 10.5 gpg |
Source: Water Quality Portal (USGS & US EPA). Water Quality Portal (USGS NWIS + EPA STORET), siteType Well, 13 analytes. 1707 wells filed a hardness value; 8 had it computed from calcium + magnesium. 180 local cells, 49 counties. 18 counties dropped for straddling the softener threshold. A county appears only when at least 3 distinct wells carry a laboratory hardness result; the 39 of Ohio’s 88 counties not listed fall short of that bar or fall under the note above, and they are left out rather than guessed at.
| County | Median (gpg) | Middle half (gpg) | mg/L CaCO3 | Rating | Wells | Samples |
|---|---|---|---|---|---|---|
| Allen | 39.3 | 33.3–41.4 | 673 | very hard | 12 | 12 |
| Ashland | 21.3 | 13.8–26.1 | 365 | very hard | 6 | 6 |
| Auglaize | 25.5 | 21.2–27.6 | 437 | very hard | 4 | 4 |
| Butler | 20.4 | 17.9–22.4 | 349 | very hard | 66 | 66 |
| Champaign | 22.4 | 20.2–24.1 | 383 | very hard | 22 | 22 |
| Clark | 22.8 | 21.4–24.3 | 390 | very hard | 28 | 28 |
| Clermont | 18.2 | 13.6–20.2 | 312 | very hard | 4 | 4 |
| Columbiana | 16.7 | 15.1–20.8 | 286 | very hard | 14 | 14 |
| Darke | 23.7 | 17.8–26 | 406 | very hard | 20 | 20 |
| Defiance | 8.7 | 149 | hard | 3 | 3 | |
| Fayette | 23.7 | 21.7–25.6 | 406 | very hard | 4 | 4 |
| Franklin | 25.1 | 21.8–29 | 430 | very hard | 126 | 126 |
| Fulton | 15.9 | 14.6–32.4 | 272 | very hard | 4 | 4 |
| Greene | 22.2 | 19.5–24 | 380 | very hard | 47 | 47 |
| Hamilton | 20.8 | 18.3–24.1 | 356 | very hard | 40 | 40 |
| Hancock | 35.6 | 26.7–70 | 609 | very hard | 5 | 5 |
| Hardin | 34.8 | 596 | very hard | 3 | 3 | |
| Harrison | 11.3 | 8.7–27.9 | 193 | very hard | 13 | 13 |
| Holmes | 18.1 | 10.9–23.4 | 310 | very hard | 4 | 4 |
| Jefferson | 18.8 | 11.8–37.4 | 322 | very hard | 22 | 22 |
| Knox | 18.3 | 14.3–19.5 | 313 | very hard | 7 | 7 |
| Licking | 20.5 | 14.6–24.8 | 351 | very hard | 27 | 27 |
| Logan | 21.5 | 20.1–23.2 | 368 | very hard | 6 | 6 |
| Madison | 24.4 | 22.4–28.2 | 418 | very hard | 8 | 8 |
| Marion | 32.5 | 29.6–45.8 | 556 | very hard | 6 | 6 |
| Medina | 12.4 | 8.4–16 | 212 | very hard | 6 | 6 |
| Mercer | 51 | 873 | very hard | 3 | 3 | |
| Miami | 21.9 | 19.3–24.2 | 375 | very hard | 44 | 44 |
| Montgomery | 21.2 | 19.3–24.7 | 363 | very hard | 154 | 154 |
| Ottawa | 25.1 | 21–64 | 430 | very hard | 6 | 6 |
| Perry | 16.7 | 11.1–19.5 | 286 | very hard | 20 | 20 |
| Pickaway | 21.6 | 20.7–23.7 | 370 | very hard | 13 | 13 |
| Pike | 20.9 | 19.5–23.3 | 358 | very hard | 54 | 54 |
| Portage | 17 | 12.3–21.8 | 291 | very hard | 40 | 40 |
| Preble | 20.4 | 18.5–22.6 | 349 | very hard | 39 | 39 |
| Putnam | 24.6 | 421 | very hard | 3 | 3 | |
| Ross | 20.9 | 17.2–23 | 358 | very hard | 7 | 7 |
| Sandusky | 24.9 | 22–56.1 | 426 | very hard | 46 | 46 |
| Shelby | 25.5 | 20.5–28.3 | 437 | very hard | 36 | 36 |
| Stark | 19.9 | 13–26.2 | 341 | very hard | 25 | 25 |
| Summit | 22.3 | 382 | very hard | 3 | 3 | |
| Tuscarawas | 22 | 18.8–93.5 | 377 | very hard | 59 | 59 |
| Union | 26 | 22.5–28.6 | 445 | very hard | 19 | 19 |
| Warren | 19.9 | 18.7–22.2 | 341 | very hard | 15 | 15 |
| Washington | 19.1 | 15–22.6 | 327 | very hard | 18 | 18 |
| Wayne | 20.4 | 15.7–22.8 | 349 | very hard | 19 | 19 |
| Williams | 17.4 | 15.1–19.8 | 298 | very hard | 64 | 64 |
| Wood | 28.9 | 22.3–39.1 | 495 | very hard | 73 | 73 |
| Wyandot | 33.6 | 26.4–83.1 | 575 | very hard | 4 | 4 |
Yes — the median across 154 measured wells, one reading each in Montgomery County is 21.2 grains per gallon (about 363 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. The middle half of those wells falls between 19.3 and 24.7 gpg, so individual wells vary widely around the median. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median across 126 measured wells, one reading each in Franklin County is 25.1 grains per gallon (about 430 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. The middle half of those wells falls between 21.8 and 29 gpg, so individual wells vary widely around the median. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median across 73 measured wells, one reading each in Wood County is 28.9 grains per gallon (about 495 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. The middle half of those wells falls between 22.3 and 39.1 gpg, so individual wells vary widely around the median. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median across 66 measured wells, one reading each in Butler County is 20.4 grains per gallon (about 349 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. The middle half of those wells falls between 17.9 and 22.4 gpg, so individual wells vary widely around the median. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median across 64 measured wells, one reading each in Williams County is 17.4 grains per gallon (about 298 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. The middle half of those wells falls between 15.1 and 19.8 gpg, so individual wells vary widely around the median. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median across 59 measured wells, one reading each in Tuscarawas County is 22 grains per gallon (about 377 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. The middle half of those wells falls between 18.8 and 93.5 gpg, so individual wells vary widely around the median. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median across 54 measured wells, one reading each in Pike County is 20.9 grains per gallon (about 358 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. The middle half of those wells falls between 19.5 and 23.3 gpg, so individual wells vary widely around the median. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median across 47 measured wells, one reading each in Greene County is 22.2 grains per gallon (about 380 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. The middle half of those wells falls between 19.5 and 24 gpg, so individual wells vary widely around the median. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median across 46 measured wells, one reading each in Sandusky County is 24.9 grains per gallon (about 426 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. The middle half of those wells falls between 22 and 56.1 gpg, so individual wells vary widely around the median. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median across 44 measured wells, one reading each in Miami County is 21.9 grains per gallon (about 375 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. The middle half of those wells falls between 19.3 and 24.2 gpg, so individual wells vary widely around the median. This is groundwater measured at other wells in the county, not a reading from any one property.
The answers above cover the 10 counties with the most measured wells; the table covers every county that clears the minimum. If your county isn’t listed, the honest answer is that the public record doesn’t hold enough well samples there for us to say — not that its water is soft.
Hard Water Feed publishes a weekly feed of newly filed domestic wells in these counties, qualified against this same hardness table and sold to one water-treatment business per territory. The territory grid shows what’s open; the category guide explains the mechanism.
Selling water treatment in Ohio? The new wells behind these figures are sold by territory — well water leads in Ohio.
Built from the same data that builds the feed, and regenerated with it — figures on this page change only when the underlying public record does.