Measured, not modelled
Measured well-water hardness for Wisconsin, 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. 2087 wells filed a hardness value; 40 had it computed from calcium + magnesium. 282 local cells, 25 counties. 6 counties dropped for straddling the softener threshold. A county appears only when at least 3 distinct wells carry a laboratory hardness result; the 47 of Wisconsin’s 72 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) | mg/L CaCO3 | Rating | Wells | Samples |
|---|---|---|---|---|---|
| Brown | 15.2 | 260 | very hard | 120 | 120 |
| Columbia | 16.6 | 284 | very hard | 117 | 117 |
| Dane | 18.7 | 320 | very hard | 157 | 157 |
| Dodge | 20.4 | 349 | very hard | 113 | 113 |
| Door | 18.1 | 310 | very hard | 47 | 47 |
| Florence | 10.5 | 180 | very hard | 18 | 18 |
| Fond Du Lac | 19.9 | 341 | very hard | 81 | 81 |
| Green | 18.1 | 310 | very hard | 26 | 26 |
| Green Lake | 19.9 | 341 | very hard | 12 | 12 |
| Jefferson | 19.3 | 330 | very hard | 81 | 81 |
| Kewaunee | 18.7 | 320 | very hard | 18 | 18 |
| Marinette | 11.7 | 200 | very hard | 35 | 35 |
| Marquette | 13.1 | 224 | very hard | 21 | 21 |
| Milwaukee | 21.6 | 370 | very hard | 118 | 118 |
| Oconto | 11.7 | 200 | very hard | 20 | 20 |
| Outagamie | 18.9 | 324 | very hard | 20 | 20 |
| Ozaukee | 19.7 | 337 | very hard | 70 | 70 |
| Racine | 16 | 274 | very hard | 49 | 49 |
| Rock | 18.7 | 320 | very hard | 58 | 58 |
| Shawano | 12 | 205 | very hard | 91 | 91 |
| Sheboygan | 21 | 359 | very hard | 74 | 74 |
| Walworth | 18.7 | 320 | very hard | 119 | 119 |
| Washington | 19.9 | 341 | very hard | 125 | 125 |
| Waukesha | 19.9 | 341 | very hard | 154 | 154 |
| Winnebago | 19.3 | 330 | very hard | 46 | 46 |
Yes — the median of 157 laboratory hardness samples from 157 measured wells in Dane County is 18.7 grains per gallon (about 320 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median of 154 laboratory hardness samples from 154 measured wells in Waukesha County is 19.9 grains per gallon (about 341 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median of 125 laboratory hardness samples from 125 measured wells in Washington County is 19.9 grains per gallon (about 341 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median of 120 laboratory hardness samples from 120 measured wells in Brown County is 15.2 grains per gallon (about 260 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median of 119 laboratory hardness samples from 119 measured wells in Walworth County is 18.7 grains per gallon (about 320 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median of 118 laboratory hardness samples from 118 measured wells in Milwaukee County is 21.6 grains per gallon (about 370 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median of 117 laboratory hardness samples from 117 measured wells in Columbia County is 16.6 grains per gallon (about 284 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median of 113 laboratory hardness samples from 113 measured wells in Dodge County is 20.4 grains per gallon (about 349 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median of 91 laboratory hardness samples from 91 measured wells in Shawano County is 12 grains per gallon (about 205 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. This is groundwater measured at other wells in the county, not a reading from any one property.
Yes — the median of 81 laboratory hardness samples from 81 measured wells in Fond Du Lac County is 19.9 grains per gallon (about 341 mg/L as CaCO3), which is “very hard” on the Water Quality Association scale. 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 Wisconsin? The new wells behind these figures are sold by territory — well water leads in Wisconsin.
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.