Hard Water Map

Minnesota Water Hardness by County

Water in Minnesota has a median hardness of 140 mg/L as CaCO₃ — "hard" on the USGS scale — based on 62,159 measurements at 7,816 monitoring stations. Lyon County has the state's hardest measured water (565.5 mg/L); Cook County the softest (19). Rank: #22 of the 50 states and D.C.

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

Of Minnesota's 87 measured counties, 65 very hard, 9 hard, 8 moderately hard, and 5 soft. The hardest are Lyon County (565.5 mg/L), Redwood County (560), and Lac qui Parle County (541). Cook County is the softest at 19 mg/L (soft).

About 87% of Minnesota's roughly 5.7 million residents in counties with gate-passing hardness data live where tap water is hard or worse.

Statewide, Minnesota's median works out to 8.2 grains per gallon and ranks #22 of the 50 states and D.C. Across 62,159 measurements at 7,816 stations — 20,151 of them since 2000 — the middle 80% of readings fall between 35 and 382 mg/L. The public record runs from 1932 to 2025.

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

Download the Minnesota water hardness map (PNG) — Water hardness by county in Minnesota: 87 counties mapped from USGS/EPA data, statewide median 140 mg/L (hard); darker counties have harder water.

By county

Water hardness by county

The table lists all 87 measured Minnesota counties, hardest first. Their medians span 565.5 mg/L in Lyon County to 19 in Cook County — a 29.8× range.

County water hardness, hardest first — median mg/L as CaCO₃.
CountyMedianBandResultsSitesNewest
Lyon County565.5Very hard148642025
Redwood County560Very hard4101102025
Lac qui Parle County541Very hard198242023
Grant County540Very hard57472023
Nobles County505.5Very hard80572023
Yellow Medicine County500Very hard436682025
Lincoln County493Very hard96392025
Renville County490Very hard274552025
Brown County480Very hard307252025
Nicollet County440Very hard264352025
Traverse County435Very hard56372023
Big Stone County430Very hard162462023
Swift County425Very hard194482025
Jackson County420Very hard321382023
Stevens County420Very hard33242023
Chippewa County410Very hard283232025
McLeod County405Very hard142482025
Carver County400Very hard450442025
Murray County390Very hard78322025
Sibley County390Very hard132312025
Le Sueur County380Very hard251462025
Pipestone County375Very hard360512023
Faribault County367.5Very hard638542019
Cottonwood County363Very hard110482025
Scott County362.5Very hard294822025
Blue Earth County360Very hard894792025
Martin County352Very hard241332025
Clay County350Very hard436702025
Rock County350Very hard132542023
Steele County340Very hard79242023
Waseca County335Very hard62202022
Rice County324.5Very hard106432025
Meeker County320Very hard427502023
Watonwan County320Very hard73432025
Pope County313Very hard135902022
Olmsted County303.5Very hard2821022024
Dodge County300Very hard17152024
Norman County300Very hard441392025
Fillmore County293Very hard158612015
Red Lake County288Very hard90322025
Freeborn County280Very hard319472023
Houston County280Very hard308312024
Marshall County280Very hard369982024
Wabasha County270Very hard186412024
Mower County268Very hard410542023
Kittson County260Very hard410692024
Dakota County252Very hard1,2752622025
Kandiyohi County250Very hard146652023
Stearns County250Very hard6821582025
Wadena County250Very hard1841012023
Goodhue County240Very hard5051002025
Polk County240Very hard6841612025
Wilkin County240Very hard310502023
Wright County240Very hard1,016752023
Otter Tail County233Very hard4392202023
Mahnomen County230Very hard92362025
Roseau County230Very hard156502024
Winona County230Very hard751492025
Pennington County228.5Very hard27202024
Hennepin County220Very hard2,6624052025
Todd County220Very hard121712025
Becker County212Very hard2231152022
Douglas County207Very hard129662025
Anoka County186Very hard2,2981652025
Beltrami County183Very hard3611162025
Sherburne County171Hard4431282024
Clearwater County170Hard256722025
Chisago County160Hard282472025
Isanti County150Hard90372020
Morrison County149Hard9341042024
Benton County147.5Hard166232024
Cass County135Hard4561322025
Ramsey County123Hard16,0501752025
Itasca County120Hard9002572025
Aitkin County110Moderately hard4141122024
Washington County105Moderately hard2,1051592025
Hubbard County100.5Moderately hard6761412025
Crow Wing County100Moderately hard3981182025
Mille Lacs County100Moderately hard115652025
Kanabec County78Moderately hard92432023
Pine County64Moderately hard6701222023
St. Louis County62Moderately hard6,5106972025
Carlton County59.3Soft3,4881462023
Lake of the Woods County49Soft287412024
Koochiching County44Soft910802025
Lake County21Soft2,3433242025
Cook County19Soft1,1642372025

ZIP codes

ZIP codes in Minnesota

The ZIP codes below are grouped by the Minnesota county they fall in. Each ZIP takes its 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.

Lyon County · 565.5 mg/L · Very hard

56115†56132†56157†56169†5617556229†56239†56258†56264

Redwood County · 560 mg/L · Very hard

5608356152†56166†56180†5621456224†56255†56263†56266†56283†5628756292†56293†56294†

Lac qui Parle County · 541 mg/L · Very hard

56212†56218†56232†56256†56257†

Grant County · 540 mg/L · Very hard

56248†56274†56309†56311†56339†56531†56590†

Nobles County · 505.5 mg/L · Very hard

56110†56117†56119†561295615356155†56165†5616856185†56187†

Yellow Medicine County · 500 mg/L · Very hard

56220†56223†56237†56241†56245†56291†56297†

Lincoln County · 493 mg/L · Very hard

56113†56136†56142†56149†56178†56280

Renville County · 490 mg/L · Very hard

55310†55314†55332†55333†55342†5623056270†5627756284†56285

Brown County · 480 mg/L · Very hard

56019†56030†56041†5607356085†56087

Nicollet County · 440 mg/L · Very hard

56003†56021†56054†56074†56082†

Traverse County · 435 mg/L · Very hard

56236†56296†56583†

Big Stone County · 430 mg/L · Very hard

56210†56211†56225†56227†56240†56276†56278†

Swift County · 425 mg/L · Very hard

56208†56215†56231†56249†56252†56271†

Jackson County · 420 mg/L · Very hard

56111†56137†5614356150†56161†56167†

Stevens County · 420 mg/L · Very hard

56207†56221†56235†56244†56267†

Chippewa County · 410 mg/L · Very hard

56222†56260†56262†56265†56295†

McLeod County · 405 mg/L · Very hard

55312†55336†55350†55354†55370†55381†55385†55395†

Carver County · 400 mg/L · Very hard

55315†5531755318†5532255339†55360†55367†55368†5538655387†5538855397†

Murray County · 390 mg/L · Very hard

56114†56122†56123†561255613156141†56151†56172†

Sibley County · 390 mg/L · Very hard

55307†55334†55335†55338†55366†55396†56044†

Le Sueur County · 380 mg/L · Very hard

56017†56028†56050†56052†56057†56058†56069†56071†56096†

Pipestone County · 375 mg/L · Very hard

56128†56139†56140†56164†56170†56186†

Faribault County · 367.5 mg/L · Very hard

56013†56014†56023†56025†56027†56033†5605156097†56098†

Cottonwood County · 363 mg/L · Very hard

56101†56118†56145†5615956174†56183

Scott County · 362.5 mg/L · Very hard

550205505455352†55372†553785537956011†

Blue Earth County · 360 mg/L · Very hard

56001†56010†56024†56034†56037†56055†56063†56065†56068†56078†5608056090†

Martin County · 352 mg/L · Very hard

56031†56039†5607556088†56121†56127†56160†56162†56171†56176†56181†

Clay County · 350 mg/L · Very hard

5651456525†5652956536†56546†56547†56549†56552†56560565625656356580†56585†

Rock County · 350 mg/L · Very hard

5611656134†56138†56144†56146†5614756156†56158†56173†

Steele County · 340 mg/L · Very hard

550495506055917†56026†56046†

Waseca County · 335 mg/L · Very hard

56048†56072†56091†56093†

Rice County · 324.5 mg/L · Very hard

55019†5502155046†55052†55053†5505755087†55088†

Meeker County · 320 mg/L · Very hard

55324†5532555329†55355†55389†56228†56243†

Watonwan County · 320 mg/L · Very hard

5602256056†56060†560625608156120

Pope County · 313 mg/L · Very hard

56226†56316†56323†56327†56334†56349†56381†56385†

Olmsted County · 303.5 mg/L · Very hard

5590155902†5590355904†5590555906†55920†55929†55932†55934†55960†55976

Dodge County · 300 mg/L · Very hard

55924†5592755940†55944†55955†55985†

Norman County · 300 mg/L · Very hard

56510†56519†5654156545†56548†56550†56574†56581†56584†

Fillmore County · 293 mg/L · Very hard

55922†55923†55935†55939†55949†55954†55962†55965†5597155975†55990†

Red Lake County · 288 mg/L · Very hard

56715†56742†56748†56750†

Freeborn County · 280 mg/L · Very hard

5600756009†56016†5602056029†56032†5603556036†5604256043†56045†56089†

Houston County · 280 mg/L · Very hard

55919†55921†55931†55941†55943†55947†55974†

Marshall County · 280 mg/L · Very hard

56710†56713†56724†56737†56738†56744†56757†56758†56760†

Wabasha County · 270 mg/L · Very hard

55041†55945†55956†55957†55964†55968†55981†55991†

Mower County · 268 mg/L · Very hard

55909†5591255918†55926†55933†55936†5595055951†55953†55961†55967†55970†55973†55977†55982†

Kittson County · 260 mg/L · Very hard

56720†56728†5672956731†56732†56733†56734†56735†56755†

Dakota County · 252 mg/L · Very hard

55024†55031†5503355044†55065†55068†550755507655077†5508555118†5512055121551225512355124551505530655337

Kandiyohi County · 250 mg/L · Very hard

5620156209†56216†56251†56253†56273†56279†56281†56282†56288†56289†

Stearns County · 250 mg/L · Very hard

55320†55353†55382†56301†5630356307†56310†56312†56320†5632156325†56331†56335†56340†56352†56356†56362†56368†56369†5637156374†56375†5637656377†56378†56387

Wadena County · 250 mg/L · Very hard

56464†56477†56481†56482†

Goodhue County · 240 mg/L · Very hard

55009†55018†55026†55027†55066†55089†55946†55963†55983†55992†

Polk County · 240 mg/L · Very hard

56517†56523†56535†5654056542†56556†56568†56592†56646†56684†56716†56721†56722†56723†56736†56762†

Wilkin County · 240 mg/L · Very hard

56520†56522†56543†56553†56565†56579†56594†

Wright County · 240 mg/L · Very hard

5530155302†5531355321†55328†553415534955358†55362†55363†5537655390†

Otter Tail County · 233 mg/L · Very hard

56324†56361†56453†56515†56518†56524†56527†56528†56533†56534†565375655156567†56571†56572†56573†56576†56586†56587†56588†

Mahnomen County · 230 mg/L · Very hard

56516†56557†56566†56589†56651†

Roseau County · 230 mg/L · Very hard

56714†56726†56751†56756†56759†56761†56763†

Winona County · 230 mg/L · Very hard

55910†55925†55952†55959†55969†55972†55979†55987†

Pennington County · 228.5 mg/L · Very hard

56701†56725†56754†

Hennepin County · 220 mg/L · Very hard

5511155305553115531655327†5533155340†5534355344†5534555346553475535655357†55359†55364553695537355374†55375†5538455391†55401554025540355404554055540655407554085540955410554115541255413554145541555416554175541855419554205542255423554245542555426554275542855429†5543055431554355543655437554385543955441†55442554435544455445554465544755450†5545455455

Todd County · 220 mg/L · Very hard

56318†56336†5634756360†56389†56434†56437†56438†56440†56446†56479†

Becker County · 212 mg/L · Very hard

5650156511†56521†56544†56554†56569†56570†56575†56578†56591†

Douglas County · 207 mg/L · Very hard

5630856315†56319†56326†56332†56343†56354†56355†

Anoka County · 186 mg/L · Very hard

55005†55011†5501455025†55070†55092†55303†55304†554215543255433554345544855449†

Beltrami County · 183 mg/L · Very hard

56601†56630†56647†56650†56663†56666†56667†56670†56678†56683†56685†56727†

Sherburne County · 171 mg/L · Hard

55308†55309†55319†55330†55398†56304†

Clearwater County · 170 mg/L · Hard

56621†56634†56644†56652†56671†56676†

Chisago County · 160 mg/L · Hard

55012†5501355032†55045†5505655069†55074†55079†55084†

Isanti County · 150 mg/L · Hard

55008†55017†55029†55040†55080†

Morrison County · 149 mg/L · Hard

56314†56328†56338†56345†56364†56373†56382†5638456443†56475†

Benton County · 147.5 mg/L · Hard

56329†56357†56367†56379†

Cass County · 135 mg/L · Hard

56435†56452†56466†56472†56473†5647456484†56626†56633†56641†56655†56662†56672†

Ramsey County · 123 mg/L · Hard

5510155102551035510455105551065510755108551095511055112†55113551145511655117551195512655127†5513055155

Itasca County · 120 mg/L · Hard

55709†55716†55721†5572255742†557445575355764†55769†55775†55781†55784†55786†55793†56628†56636†56637†56639†56657†56659†56680†56681†56688†

Aitkin County · 110 mg/L · Moderately hard

5574855752†55760†55785†55787†56342†56350†56431†56469†

Washington County · 105 mg/L · Moderately hard

55001†55003550165503855042†5504355047†5505555071†55073†550825509055115551255512855129

Hubbard County · 100.5 mg/L · Moderately hard

56433†56458†56461†56467†56470†

Crow Wing County · 100 mg/L · Moderately hard

56401†5642556441†56442†56444†56447†56448†56449†56450†56455†56465†56468†

Mille Lacs County · 100 mg/L · Moderately hard

55371†5631356330†56353†56359†56363†56386†

Kanabec County · 78 mg/L · Moderately hard

55006†55007†55051†56358†

Pine County · 64 mg/L · Moderately hard

55030†55036†55037†55063†55072†55704†55712†55735†55756†55783†55795†

St. Louis County · 62 mg/L · Moderately hard

55602†55702†55703†55705†55706†5570855710†55711†55713†55717†55719†55723†55724†55725†55732†55734†55736†55738†55741†55746†55750†55751†55758†55763†55765†55768†55771†55779†55782†55790†55792†55802†55803†55804†55805558065580755808†55810†558115581255814†

Carlton County · 59.3 mg/L · Soft

55707†55718†55720†55726†55733†55749†55757†5576755780†55797†55798†

Lake of the Woods County · 49 mg/L · Soft

56623†56673†56686†56711†

Koochiching County · 44 mg/L · Soft

5577256627†56629†56649†56653†56654†56658†56660†56661†5666856669†

Lake County · 21 mg/L · Soft

55601†55603†55607†55609†55614†55616†55731†55796†

Cook County · 19 mg/L · Soft

55604†55605†55606†55612†55613†55615†

† 681 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

Minnesota's groundwater measures harder than its surface water — 286 mg/L across 4,311 samples versus 132 across 56,739, about 2.2× harder. Wells draw from groundwater, so well owners in Minnesota tend to see the harder number — 286 mg/L, very hard. Groundwater readings there run 130 to 540.3 mg/L across the middle 80% of samples. The comparison draws on 3,251 groundwater and 4,515 surface-water monitoring sites; 14 readings above 2,000 mg/L were logged but held out of the medians as outliers.

Groundwater (wells)

286 mg/L as CaCO₃ · 4,311 results at 3,251 stations.

Surface water (rivers, lakes)

132 mg/L as CaCO₃ · 56,739 results at 4,515 stations.

Groundwater measures about 2.2× harder than surface water here.

Chemistry

Water chemistry in Minnesota

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

TDS

207 mg/L · n=42,529

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

pH

7.8 pH · n=182,999

pH 7.8 — within the EPA secondary range of 6.5–8.5, on the alkaline side.

Alkalinity

120 mg/L as CaCO3 · n=26,352

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

Calcium : Magnesium

57.6 : 23.2 mg/L ≈ 2.48 : 1 · n=11,101

Calcium is about 60% of Minnesota's hardness (57.6 mg/L Ca to 23.2 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 Minnesota

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

  • Cambrian-Ordovician aquifer system — median 317 mg/L across 139 samples at 77 sites: very hard.
  • Upper carbonate aquifer — median 292 mg/L across 11 samples at 9 sites: very hard.
  • Sand and gravel aquifers (glaciated regions) — median 288 mg/L across 781 samples at 363 sites: very hard.

Together these systems account for 931 measured samples at 449 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

1950s2020s210

Minnesota's decade median moved from 71 mg/L in the 1950s to 210 in the 2020s. Over the series, the decade median peaked at 210 mg/L in the 1960s and bottomed at 71 in the 1950s. Decade medians reflect where and what agencies sampled in each era, not just changes in the water itself.

Scale

Where Minnesota sits on the scale

On the USGS scale, Minnesota's 140 mg/L is hard — 8.2 grains per gallon, above the 120 mg/L hard cutoff, below very hard.

SoftModerately hardHardVery hard60 · 3.5 gpg120 · 7.0 gpg180 · 10.5 gpg140 mg/L — Hard
Harder than 50% of the 2,977 measured county medians.

At 140 mg/L (8.2 gpg), water-softener owners in Minnesota typically set their unit to this hardness — settings calculator.

Questions

Frequently asked questions

Is Minnesota's water hard?
Minnesota's median hardness is 140 mg/L as CaCO₃, "hard" on the USGS scale and 1× the national county median of 140 mg/L. About 87% of residents in measured counties have hard-or-worse water.
Which county in Minnesota has the hardest water?
Lyon County, with a median of 565.5 mg/L as CaCO₃ across 148 measurements.
Is well water harder than city water in Minnesota?
Groundwater measures harder here — about 2.2× the surface water — so wells tend to run harder (groundwater 286 vs surface water 132 mg/L).
How do I find my exact hardness in Minnesota?
Search your ZIP on the lookup tool, read your utility's Consumer Confidence Report, or test at home with a kit.
Is Minnesota's water harder than the national average?
Yes. Minnesota's median of 140 mg/L is 1× the national county median of 140 mg/L, and Minnesota ranks #22 of the 50 states and D.C.

Compare

States with similar hardness

Two states measure closest to Minnesota's 140 mg/L: California at 150 mg/L and Idaho at 130 mg/L. Minnesota measures harder than 58% 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 — 62,159 Minnesota measurements. Data last verified . Methodology.

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