Hard Water Map

Wisconsin Water Hardness by County

Water in Wisconsin has a median hardness of 110 mg/L as CaCO₃ — "moderately hard" on the USGS scale — based on 33,134 measurements at 6,437 monitoring stations. Iowa County has the state's hardest measured water (390 mg/L); Lincoln County the softest (13.6). Rank: #26 of the 50 states and D.C.

Wisconsin water hardness map — what the numbers mean. Data verified 2026-07-22.

Of Wisconsin's 72 measured counties, 35 very hard, 7 hard, 17 moderately hard, and 13 soft. The hardest are Iowa County (390 mg/L), Calumet County (380), and Lafayette County (350). Lincoln County is the softest at 13.6 mg/L (soft).

About 74% of Wisconsin's roughly 5.9 million residents in counties with gate-passing hardness data live where tap water is hard or worse.

Statewide, Wisconsin's median works out to 6.4 grains per gallon and ranks #26 of the 50 states and D.C. Across 33,134 measurements at 6,437 stations — 11,905 of them since 2000 — the middle 80% of readings fall between 27 and 340 mg/L. The public record runs from 1901 to 2026.

See where Wisconsin sits nationally on the national map, or what its number means on the hardness scale.

Download the Wisconsin water hardness map (PNG) — Water hardness by county in Wisconsin: 72 counties mapped from USGS/EPA data, statewide median 110 mg/L (moderately hard); darker counties have harder water.

By county

Water hardness by county

The table lists all 72 measured Wisconsin counties, hardest first. Their medians span 390 mg/L in Iowa County to 13.6 in Lincoln County — a 28.7× range.

County water hardness, hardest first — median mg/L as CaCO₃.
CountyMedianBandResultsSitesNewest
Iowa County390Very hard219522000
Calumet County380Very hard71432007
Lafayette County350Very hard139712004
Kewaunee County340Very hard115372018
Ozaukee County340Very hard145832013
Dodge County330Very hard2051322014
Fond du Lac County330Very hard2101202026
Washington County320Very hard4211662023
Rock County316.5Very hard214702018
Sheboygan County315Very hard5751182013
Green County310Very hard143312004
Jefferson County310Very hard1891082014
Manitowoc County310Very hard407962025
Door County300Very hard95572008
Grant County300Very hard510902014
Columbia County280Very hard2171272015
Waukesha County275Very hard8722252026
Racine County274.5Very hard392742023
Crawford County270Very hard139472010
Richland County260Very hard55242004
Walworth County257Very hard7511672026
Vernon County250Very hard295672024
Kenosha County241Very hard223552024
Outagamie County231Very hard297632015
Pierce County230Very hard217622023
Green Lake County222Very hard127282023
Milwaukee County220Very hard1,9451942023
Waupaca County218.5Very hard242642026
Brown County198Very hard1,3581972020
Marquette County190Very hard73332026
Winnebago County190Very hard254712015
Buffalo County180Very hard176352024
St. Croix County180Very hard4641512023
Sauk County180Very hard182542019
Waushara County180Very hard203882026
Adams County160Hard68302023
Oconto County160Hard248422026
La Crosse County150Hard280512014
Shawano County144Hard9281632026
Menominee County140Hard8271562022
Marinette County123Hard597612020
Portage County120Hard7171802026
Dunn County110Moderately hard232652014
Forest County110Moderately hard5261582025
Langlade County110Moderately hard272812026
Monroe County110Moderately hard66292004
Polk County95Moderately hard6451162023
Florence County92.3Moderately hard888432023
Taylor County85Moderately hard26182001
Wood County79Moderately hard3751892004
Washburn County74.5Moderately hard114412026
Clark County74Moderately hard211442004
Barron County72Moderately hard174832025
Burnett County68Moderately hard351972025
Trempealeau County68Moderately hard309452014
Pepin County62.9Moderately hard318202016
Ashland County62Moderately hard4,4812132021
Dane County61.4Moderately hard1,8402732020
Juneau County60Moderately hard94242004
Eau Claire County57Soft220632014
Iron County56Soft504502019
Sawyer County54Soft118442001
Marathon County51Soft134452026
Chippewa County46Soft450892013
Rusk County46Soft149632025
Price County45.5Soft64242006
Jackson County40Soft232352003
Vilas County38.9Soft1,7773162026
Oneida County35Soft178712026
Bayfield County23.5Soft9191232025
Douglas County20Soft1,3231452025
Lincoln County13.6Soft332462013
7 additional results from sites without county attribution (not shown).

ZIP codes

ZIP codes in Wisconsin

The ZIP codes below are grouped by the Wisconsin county each mostly falls within (by land area). Each ZIP takes that county's measured median — shown in the group header — so this is a ZIP-to-county guide, not a separate reading for every ZIP. To check the water system serving a specific address, use the lookup.

Key: a † after a ZIP means it has no mapped community water system — usually a private-well area. Plain ZIPs are served by a mapped community water system.

Iowa County · 390 mg/L · Very hard

53503†53506†53507†53526†53533†53543†53544†53553†53565†53580†53582†

Calumet County · 380 mg/L · Very hard

5301453061†530885411054123†54129†54160†541695491554952†

Lafayette County · 350 mg/L · Very hard

5350453510†53516†5353053541†5358653587†53599†53803†

Kewaunee County · 340 mg/L · Very hard

54201†54205†54216†54217†

Ozaukee County · 340 mg/L · Very hard

53004†53012†53021†5302453074†53080†53092†53097†

Dodge County · 330 mg/L · Very hard

53003†53006†530165303253034†53035†53039†53047†53048†53050†53059†53078†53091†53098†53099†53557†53579†53916†53922†53933†

Fond du Lac County · 330 mg/L · Very hard

53010†53019†53049†53057†53065†53079†53919†539315396354932†54935549375497154974†54979†

Washington County · 320 mg/L · Very hard

53002†53017†530225302753033†5303753040†53076†5308653090†53095

Rock County · 316.5 mg/L · Very hard

53501†53505†53511†53520†53525†53534†53536†535375354553546†53548†5356353576†

Sheboygan County · 315 mg/L · Very hard

53001†53011†53013†53020†53023†53031530445307053073†53075†5308153083†53085†53093†

Green County · 310 mg/L · Very hard

53502†53521†53522†53550†5356653570†53574†

Jefferson County · 310 mg/L · Very hard

53036†5303853094†53137†53156†53178†53538†53549†5355153594†

Manitowoc County · 310 mg/L · Very hard

53015†53042†53063†54207†54214†5421554220†5422754228†54230†5423254241†54245†54247†

Door County · 300 mg/L · Very hard

54202†54204†54209†54210†54211†54212†54213†54234†5423554246†

Grant County · 300 mg/L · Very hard

53554†53569†53573†53801†53802†53804†53805†53806†53807†53808†53809†53810†53811†538125381353816†538175381853820†53825†53827†

Columbia County · 280 mg/L · Very hard

53555†5390153911†53923†53925†53928†53932†5393553954†5395553956†53960†53969

Waukesha County · 275 mg/L · Very hard

530055300753018†53029†5304553046†5305153058†5306653069†5307253089†53103†53118†53119†53122†53127†53146†5314953150†5315153153†53183531865318853189†

Racine County · 274.5 mg/L · Very hard

5310553108†53126†53139†53167†531775318253185†53402†53403534045340553406

Crawford County · 270 mg/L · Very hard

53821†53826†54626†54628†54631†54645†54654†54655†54657†

Richland County · 260 mg/L · Very hard

53518†53540†53556†53581†53584†53924†54664†

Walworth County · 257 mg/L · Very hard

53114†53115†53120†53121†5312553128†53147†5315753176†53184†53190†5319153195†53585†

Vernon County · 250 mg/L · Very hard

54621†54624†54632†54634†54639†54651†54652†54658†54665†54667†

Kenosha County · 241 mg/L · Very hard

53104†5314053142†531435314453158†53168†53170†53179†53181†53192†

Outagamie County · 231 mg/L · Very hard

54106†5411354130541365414054152†5416554170†5491154913†5491454922†54931†5494254944†

Pierce County · 230 mg/L · Very hard

54003†54011†54014†54021†5402254723†54740†54750†54761†54767†

Green Lake County · 222 mg/L · Very hard

53926†53939†53946†53947†54941†54968†

Milwaukee County · 220 mg/L · Very hard

5311053129†53130†531325315453172532025320353204532055320653207†5320853209†5321053211532125321353214532155321653217†53218†5321953220†53221†53222†53223†53224†5322553226†5322753228†5323353235†53295†

Waupaca County · 218.5 mg/L · Very hard

54926†54929†54933†54945†5494654949†54950†54961†54962†54977†54981†54983

Brown County · 198 mg/L · Very hard

54115†54126†54155†54173†54180†54208†54229†543015430254303543045430754311†54313†

Marquette County · 190 mg/L · Very hard

53920†53930†53949†53952†5395353964†54960†

Winnebago County · 190 mg/L · Very hard

5490154902†54904†54927†54947†54956†54963†54964†54980†54985†54986†

Buffalo County · 180 mg/L · Very hard

54610†54622†54629†5475554756†

St. Croix County · 180 mg/L · Very hard

5400254007†54013†54015†54016†5401754023†54025†54027†5402854082†

Sauk County · 180 mg/L · Very hard

53561†53577†53578†53583†5358853913†53937†53940†53941†53942†53943†53951†5395953961†

Waushara County · 180 mg/L · Very hard

54923†54930†54940†54943†54965†54966†54967†54970†5498254984†

Adams County · 160 mg/L · Hard

53910†53934†53936†53965†54457†54613†

Oconto County · 160 mg/L · Hard

54101†54124†54138†54139†54141†54149†54153†54154†54161†54171†54174†54175†

La Crosse County · 150 mg/L · Hard

54601†54603†54614†54623†54636†54644†5465054653†54669†

Shawano County · 144 mg/L · Hard

54107†54111†54127†54128†54137†54162†54166†54414†54416†5445054486†54499†54928†54948†54978†

Menominee County · 140 mg/L · Hard

54135†54150†

Marinette County · 123 mg/L · Hard

54102†54104†54112†54114†54119†54125†54143†54151†54156†54157†54159†54177†

Portage County · 120 mg/L · Hard

54406†54407†54423†54443†54458†54467†54473†54481†54482†54909†54921†

Dunn County · 110 mg/L · Moderately hard

54725†54730†54734†54737†54739†54749†54751†54763†54772†

Forest County · 110 mg/L · Moderately hard

54103†54465†54511†54520†54541†54542†54566†

Langlade County · 110 mg/L · Moderately hard

54409†54418†54424†54428†54430†54462†54464†54485†54491†

Monroe County · 110 mg/L · Moderately hard

54619†54638†54648†54656†5466054666†54670†

Polk County · 95 mg/L · Moderately hard

54001†54005†54006†54009†54020†54024†54026†54810†54824†54826†54837†54853†54858†54889†

Florence County · 92.3 mg/L · Moderately hard

54120†54121†

Taylor County · 85 mg/L · Moderately hard

54433†54447†54451†54470†54480†54490†54766†

Wood County · 79 mg/L · Moderately hard

54410†54412†54413†54441†54449†54454†54466†5446954475†54489†54494†54495†

Washburn County · 74.5 mg/L · Moderately hard

54801†54817†54859†54870†54871†54875†54888†

Clark County · 74 mg/L · Moderately hard

54420†54422†54425†54436†54437†54446†54456†54460†54479†54488†54493†54498†54746†54771†

Barron County · 72 mg/L · Moderately hard

54004†54728†54733†54762†54805†54812†54822†54829†5484154857†54868†

Burnett County · 68 mg/L · Moderately hard

54813†54830†54840†54845†54872†54893†

Trempealeau County · 68 mg/L · Moderately hard

5461254616†54625†54627†54630†54661†54747†54758†5476054770†54773†

Pepin County · 62.9 mg/L · Moderately hard

54721†54736†54759†54769†

Ashland County · 62 mg/L · Moderately hard

54514†54517†54527†54546†54806†54846†54850†54855†54861†

Dane County · 61.4 mg/L · Moderately hard

53508†53515†53517†53523†53527†5352853529†53531†5353253558†53559†53560†53562†53571†53572†5357553589†5359053593†53597535985370353704537055370653711†537135371453715537165371753718537195372653792

Juneau County · 60 mg/L · Moderately hard

53929†53944†53948†53950†5396253968†54618†5463754646†

Eau Claire County · 57 mg/L · Soft

54701†547035472054722†54738†54741†54742

Iron County · 56 mg/L · Soft

54525†54534†54536†54547†54550†54559†54565†

Sawyer County · 54 mg/L · Soft

54828†54835†54843†54862†54867†54876†54896†

Marathon County · 51 mg/L · Soft

5440154403†54405†54408†54411†54417†54421†54426†54427†54440†544485445554471†5447454476†54484

Chippewa County · 46 mg/L · Soft

5472454726†547275472954732†54745†54748†54757†54768

Rusk County · 46 mg/L · Soft

54526†54530†54563†54731†54819†54848†54895†

Price County · 45.5 mg/L · Soft

54459†54513†54515†54524†54537†54552†54555†54556†

Jackson County · 40 mg/L · Soft

54611†54615†54635†54642†54643†54659†54754†

Vilas County · 38.9 mg/L · Soft

54512†54519†5452154538†54540†54545†54554†54557†54558†54560†54561†54568†

Oneida County · 35 mg/L · Soft

54463†54501†54529†54531†54539†54548†54562†54564†

Bayfield County · 23.5 mg/L · Soft

54814†54821†54827†54832†54839†54844†54847†54856†54865†54891†

Douglas County · 20 mg/L · Soft

54820†54836†54838†54842†54849†54854†54864†54873†54874†54880†

Lincoln County · 13.6 mg/L · Soft

54435†54442†54452†54487†

† 629 ZIP codes are not served by a mapped community water system — most are private-well areas. See well water hardness.

Check any ZIP's utility and hardness →

Source

Groundwater vs surface water

Wisconsin's groundwater measures harder than its surface water — 210 mg/L across 7,865 samples versus 94.4 across 24,156, about 2.2× harder. Wells draw from groundwater, so well owners in Wisconsin tend to see the harder number — 210 mg/L, very hard. Groundwater readings there run 18.3 to 400 mg/L across the middle 80% of samples. The comparison draws on 3,977 groundwater and 2,360 surface-water monitoring sites; 29 readings above 2,000 mg/L were logged but held out of the medians as outliers.

Groundwater (wells)

210 mg/L as CaCO₃ · 7,865 results at 3,977 stations.

Surface water (rivers, lakes)

94.4 mg/L as CaCO₃ · 24,156 results at 2,360 stations.

Groundwater measures about 2.2× harder than surface water here.

Chemistry

Water chemistry in Wisconsin

Beyond the hardness number, Wisconsin's water carries a fuller chemical signature — here is how its measured parameters compare to national benchmarks.

TDS

96 mg/L · n=8,892

96 mg/L — below the national county median of 226.

pH

7.9 pH · n=46,834

pH 7.9 — within the EPA secondary range of 6.5–8.5, on the alkaline side.

Alkalinity

117 mg/L as CaCO3 · n=5,997

117 mg/L — substantial buffering capacity, which resists pH swings.

Calcium : Magnesium

26.2 : 12.6 mg/L ≈ 2.08 : 1 · n=9,522

Calcium is about 56% of Wisconsin's hardness (26.2 mg/L Ca to 12.6 mg/L Mg), a little more magnesium-rich than the national ~68% calcium share.

Parameter medians may include a small share of quality-control samples; the hardness lane is fully QC-filtered.

Aquifers

Major aquifers under Wisconsin

3 aquifer systems supply much of Wisconsin's measured groundwater.

  • Silurian-Devonian aquifers — median 340 mg/L across 615 samples at 438 sites: very hard.
  • Cambrian-Ordovician aquifer system — median 280 mg/L across 1,845 samples at 1,056 sites: very hard.
  • Sand and gravel aquifers (glaciated regions) — median 120 mg/L across 3,634 samples at 1,672 sites: hard.

Together these systems account for 6,094 measured samples at 3,166 sites. Aquifer medians pool samples across a whole system and can mask local variation — see the national aquifer map for how these compare across states.

Trend

Hardness over time

1930s2020s310

Wisconsin's decade median moved from 310 mg/L in the 1930s to 125.5 in the 2020s. Over the series, the decade median peaked at 310 mg/L in the 1930s and bottomed at 64 in the 2010s. Decade medians reflect where and what agencies sampled in each era, not just changes in the water itself.

Scale

Where Wisconsin sits on the scale

On the USGS scale, Wisconsin's 110 mg/L is moderately hard — 6.4 grains per gallon, between the 60 and 120 mg/L soft and hard cutoffs.

SoftModerately hardHardVery hard60 · 3.5 gpg120 · 7.0 gpg180 · 10.5 gpg110 mg/L — Moderately hard
Harder than 43% of the 2,977 measured county medians.

Questions

Frequently asked questions

Is Wisconsin's water hard?
Wisconsin's median hardness is 110 mg/L as CaCO₃, "moderately hard" on the USGS scale and below the national county median of 140 mg/L. About 74% of residents in measured counties have hard-or-worse water.
Which county in Wisconsin has the hardest water?
Iowa County, with a median of 390 mg/L as CaCO₃ across 219 measurements.
Is well water harder than city water in Wisconsin?
Groundwater measures harder here — about 2.2× the surface water — so wells tend to run harder (groundwater 210 vs surface water 94.4 mg/L).
How do I find my exact hardness in Wisconsin?
Search your ZIP on the lookup tool, read your utility's Consumer Confidence Report, or test at home with a kit.
Is Wisconsin's water harder than the national average?
No. Wisconsin's median of 110 mg/L is below the national county median of 140 mg/L; it ranks #26 of the 50 states and D.C.

Compare

States with similar hardness

Two states measure closest to Wisconsin's 110 mg/L: District of Columbia at 113 mg/L and Kentucky at 120 mg/L. Wisconsin measures harder than 50% of states. Browse the full ranking on the statistics page.

More: hardness scale · check your address · national statistics · the national map.

By . Source: USGS/EPA Water Quality Portal — 33,134 Wisconsin measurements. Data last verified . Methodology.

Cite this page: “Wisconsin Water Hardness by County.” Hard Water Map. Retrieved 2026-07-22, https://hardwatermap.com/water-hardness/wisconsin/