Hard Water Map

Oregon Water Hardness by County

Water in Oregon has a median hardness of 48.1 mg/L as CaCO₃ — "soft" on the USGS scale — based on 50,168 measurements at 7,348 monitoring stations. Malheur County has the state's hardest measured water (272 mg/L); Lane County the softest (18). Rank: #37 of the 50 states and D.C.

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

Of Oregon's 36 measured counties, 2 very hard, 2 hard, 9 moderately hard, and 23 soft. The hardest are Malheur County (272 mg/L), Morrow County (235), and Umatilla County (142). Lane County is the softest at 18 mg/L (soft).

About 4% of Oregon's roughly 4.2 million residents in counties with gate-passing hardness data live where tap water is hard or worse.

Statewide, Oregon's median works out to 2.8 grains per gallon and ranks #37 of the 50 states and D.C. Across 50,168 measurements at 7,348 stations — 17,214 of them since 2000 — the middle 80% of readings fall between 16 and 300 mg/L. The public record runs from 1903 to 2025.

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

Download the Oregon water hardness map (PNG) — Water hardness by county in Oregon: 36 counties mapped from USGS/EPA data, statewide median 48.1 mg/L (soft); darker counties have harder water.

By county

Water hardness by county

The table lists all 36 measured Oregon counties, hardest first. Their medians span 272 mg/L in Malheur County to 18 in Lane County — a 15.1× range.

County water hardness, hardest first — median mg/L as CaCO₃.
CountyMedianBandResultsSitesNewest
Malheur County272Very hard2,7242482025
Morrow County235Very hard1,1331742025
Umatilla County142Hard3,2545912025
Crook County122Hard364762025
Baker County104Moderately hard478462025
Grant County104Moderately hard383222025
Gilliam County94.4Moderately hard300612024
Jackson County81.5Moderately hard1,9014962025
Wheeler County76Moderately hard7652024
Wasco County68Moderately hard8971332025
Multnomah County66Moderately hard3,9553102025
Sherman County65.1Moderately hard489252024
Josephine County63Moderately hard1,3642302025
Washington County59.4Soft2,5423002025
Harney County58.7Soft7933272025
Columbia County53.2Soft620752025
Lake County51.2Soft357552025
Marion County51Soft3,1453162025
Benton County44Soft1,4261712025
Jefferson County44Soft606892025
Klamath County44Soft1,5802632025
Union County42Soft5431242025
Douglas County40Soft3,1435112025
Curry County38Soft1,087852025
Yamhill County37Soft2,0182192025
Clatsop County30.8Soft6201482025
Deschutes County30.1Soft1,4233872025
Clackamas County28Soft2,5414072025
Coos County26Soft1,1152882025
Wallowa County26Soft469602024
Hood River County25.1Soft7581302025
Polk County24Soft5041222024
Tillamook County22.4Soft1,2551852025
Lincoln County22Soft9431162025
Linn County21Soft1,7232142024
Lane County18Soft3,6393392025

ZIP codes

ZIP codes in Oregon

The ZIP codes below are grouped by the Oregon 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.

Malheur County · 272 mg/L · Very hard

89421†97901†97902†97903†97906†97908†97909†97910†97911†97913†97914†97917†97918†97920†

Morrow County · 235 mg/L · Very hard

97818†97836†97839†97843†97844†

Umatilla County · 142 mg/L · Hard

9780197810†97813†97826†97835†9783897859†97862†97868†97875†97880†97882†97886†

Crook County · 122 mg/L · Hard

97751†97752†97753†97754†

Baker County · 104 mg/L · Moderately hard

97814†97819†97833†97834†97837†97840†97870†97884†97905†97907†

Grant County · 104 mg/L · Moderately hard

97817†97820†97825†97845†97848†97856†97864†97865†97869†97873†97877†

Gilliam County · 94.4 mg/L · Moderately hard

97812†97823†

Jackson County · 81.5 mg/L · Moderately hard

97501†97502†97503†97504†97520†97522†97524†9752597530†97535†97536†97537†97539†97540†97541†

Wheeler County · 76 mg/L · Moderately hard

97750†97830†97874†

Wasco County · 68 mg/L · Moderately hard

97001†97021†97037†97040†9705797058†97063†97761†

Multnomah County · 66 mg/L · Moderately hard

97019†970249703097060†97080972019720297203†972049720597206972089720997210†97211972129721397214972159721697217†97218972199722097221972279723097231†972329723397236†9723997258†97266

Sherman County · 65.1 mg/L · Moderately hard

97029†97033†97039†97050†97065†

Josephine County · 63 mg/L · Moderately hard

97497†97523†97526†97527†97531†97532†97534†97538†97543†97544†

Washington County · 59.4 mg/L · Soft

970039700597006†97007†97008970629707897106†97109†97113†97116†97117†97119†97123†97124†97125†97133†9714097144†97223972249722597229

Harney County · 58.7 mg/L · Soft

97710†97720†97721†97722†97732†97736†97738†97758†97904†

Columbia County · 53.2 mg/L · Soft

97016†9701897048†97051†97053†97054†97056†97064†

Lake County · 51.2 mg/L · Soft

97620†97630†97636†97637†97638†97640†97641†97735†

Marion County · 51 mg/L · Soft

97002†9702097026†97032†97071†97137†97301973029730397305†97306†9731097317†97325†97342†97346†97352†97358†97362†97373†97375†97381†97383†9738497385†97392†

Benton County · 44 mg/L · Soft

97324†97330†9733197333†97370†97456†

Jefferson County · 44 mg/L · Soft

97711†97730†97734†97741†

Klamath County · 44 mg/L · Soft

97601†97603†97604†97621†97622†97623†97624†97625†97626†97627†97632†97633†97634†97639†97731†97733†97737†

Union County · 42 mg/L · Soft

97824†97827†97841†97850†97867†97876†97883†

Douglas County · 40 mg/L · Soft

97410†97416†97417†97429†9743297435†97436†97441†97442†97443†97447†97457†97462†97467†97469†9747097471†97473†97479†97481†97484†97486†97494†97495†97496†97499†

Curry County · 38 mg/L · Soft

97406†97415†97444†97450†97465†97476†

Yamhill County · 37 mg/L · Soft

97101†97111†97114†971159712797128†97132†97148†97347†97378†97396†

Clatsop County · 30.8 mg/L · Soft

97102†97103†9711097121†97138†97145†97146†

Deschutes County · 30.1 mg/L · Soft

97701†9770297703†97707†97709†97712†97739†9775697760†

Clackamas County · 28 mg/L · Soft

97004†9700997011†97013†9701597017†97022†97023†9702797028†970349703597038†97042†9704597049†97055†97067†970689707097086970899722297267

Coos County · 26 mg/L · Soft

97411†97414†97420†97423†97449†97458†97459†97466†

Wallowa County · 26 mg/L · Soft

97828†97842†97846†97857†97885†

Hood River County · 25.1 mg/L · Soft

97014†97031†97041†

Polk County · 24 mg/L · Soft

973049733897344†97351†9736197371†

Tillamook County · 22.4 mg/L · Soft

97107†97108†97112†9711897122†9713097131†9713497135†97136†97141†9714797149†

Lincoln County · 22 mg/L · Soft

97326†97341†97343†97357†9736497365†97366†97367†97368†97369†97376†97380†97388†97390†97391†97394†

Linn County · 21 mg/L · Soft

9732197322†97327†97329†97335†97336†97345†97348†97350†97355†9736097374†97377†97386†97389†97446†97759†

Lane County · 18 mg/L · Soft

9740197402†974039740497405†9740897412†97413†97419†97424†97426†97430†97431†97434†97437†97438†97439†97448†97451†97452†97453†97454†97455†97461†97463†9747797478†97480†97487†97488†97489†97490†97492†97493†97498†

† 346 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

Oregon's groundwater measures harder than its surface water — 152 mg/L across 16,392 samples versus 31 across 32,695, about 4.9× harder. Wells draw from groundwater, so well owners in Oregon tend to see the harder number — 152 mg/L, hard. Groundwater readings there run 34.4 to 500 mg/L across the middle 80% of samples. The comparison draws on 4,118 groundwater and 2,893 surface-water monitoring sites; 458 readings above 2,000 mg/L were logged but held out of the medians as outliers.

Groundwater (wells)

152 mg/L as CaCO₃ · 16,392 results at 4,118 stations.

Surface water (rivers, lakes)

31 mg/L as CaCO₃ · 32,695 results at 2,893 stations.

Groundwater measures about 4.9× harder than surface water here.

Chemistry

Water chemistry in Oregon

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

TDS

152 mg/L · n=6,687

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

pH

7.6 pH · n=26,686

pH 7.6 — within the EPA secondary range of 6.5–8.5, on the alkaline side.

Alkalinity

42 mg/L as CaCO3 · n=41,883

42 mg/L — modest buffering capacity.

Calcium : Magnesium

15.3 : 6.1 mg/L ≈ 2.51 : 1 · n=19,350

Calcium is about 60% of Oregon's hardness (15.3 mg/L Ca to 6.1 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 Oregon

Two aquifer systems supply much of Oregon's measured groundwater.

  • Willamette Lowland basin-fill aquifers — median 105 mg/L across 175 samples at 86 sites: moderately hard.
  • Columbia Plateau basaltic-rock aquifers — median 73 mg/L across 115 samples at 95 sites: moderately hard.

Together these systems account for 290 measured samples at 181 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

1950s2020s75

Oregon's decade median moved from 28 mg/L in the 1950s to 45.1 in the 2020s. Over the series, the decade median peaked at 75 mg/L in the 1990s and bottomed at 28 in the 1950s. Decade medians reflect where and what agencies sampled in each era, not just changes in the water itself.

Scale

Where Oregon sits on the scale

On the USGS scale, Oregon's 48.1 mg/L is soft — 2.8 grains per gallon, below the 60 mg/L soft cutoff — among the softest water measured in the US.

SoftModerately hardHardVery hard60 · 3.5 gpg120 · 7.0 gpg180 · 10.5 gpg48.1 mg/L — Soft
Harder than 25% of the 2,977 measured county medians.

Questions

Frequently asked questions

Is Oregon's water hard?
Oregon's median hardness is 48.1 mg/L as CaCO₃, "soft" on the USGS scale and below the national county median of 140 mg/L.
Which county in Oregon has the hardest water?
Malheur County, with a median of 272 mg/L as CaCO₃ across 2,724 measurements.
Is well water harder than city water in Oregon?
Groundwater measures harder here — about 4.9× the surface water — so wells tend to run harder (groundwater 152 vs surface water 31 mg/L).
How do I find my exact hardness in Oregon?
Search your ZIP on the lookup tool, read your utility's Consumer Confidence Report, or test at home with a kit.
Is Oregon's water harder than the national average?
No. Oregon's median of 48.1 mg/L is below the national county median of 140 mg/L; it ranks #37 of the 50 states and D.C.

Compare

States with similar hardness

Two states measure closest to Oregon's 48.1 mg/L: Alabama at 48.4 mg/L and Vermont at 46.5 mg/L. Oregon measures harder than 28% 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 — 50,168 Oregon measurements. Data last verified . Methodology.

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