Hard Water Map

Louisiana Water Hardness by County

Water in Louisiana has a median hardness of 90 mg/L as CaCO₃ — "moderately hard" on the USGS scale — based on 81,193 measurements at 12,387 monitoring stations. St. Bernard County has the state's hardest measured water (500 mg/L); St. Helena County the softest (6). Rank: #27 of the 50 states and D.C.

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

Of Louisiana's 64 measured counties, 5 very hard, 16 hard, 16 moderately hard, and 27 soft. The hardest are St. Bernard County (500 mg/L), Red River County (260), and Franklin County (197). St. Helena County is the softest at 6 mg/L (soft).

About 35% of Louisiana's roughly 4.6 million residents in counties with gate-passing hardness data live where tap water is hard or worse.

Statewide, Louisiana's median works out to 5.3 grains per gallon and ranks #27 of the 50 states and D.C. Across 81,193 measurements at 12,387 stations — 38,201 of them since 2000 — the middle 80% of readings fall between 11 and 460 mg/L. The public record runs from 1902 to 2026.

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

Download the Louisiana water hardness map (PNG) — Water hardness by county in Louisiana: 64 counties mapped from USGS/EPA data, statewide median 90 mg/L (moderately hard); darker counties have harder water.

By county

Water hardness by county

The table lists all 64 measured Louisiana counties, hardest first. Their medians span 500 mg/L in St. Bernard County to 6 in St. Helena County — a 83.3× range.

County water hardness, hardest first — median mg/L as CaCO₃.
CountyMedianBandResultsSitesNewest
St. Bernard County500Very hard1,325642023
Red River County260Very hard1,4281362023
Franklin County197Very hard7653142024
Cameron County190Very hard1,4341882024
Orleans County190Very hard1,8562112023
Jefferson County165Hard1,5932112024
Plaquemines County164Hard2,0641192024
Terrebonne County154Hard2,6561072024
Bossier County150Hard2,5552992024
Natchitoches County149.5Hard1,8523242024
St. Charles County147Hard1,5691432024
Iberia County143Hard8901032023
Iberville County140Hard1,6242362024
St. James County140Hard7851602022
Vermilion County140Hard1,9241972024
West Feliciana County140Hard1,5771132024
Lafourche County132Hard1,676672024
Avoyelles County130Hard1,7924152024
Madison County130Hard402512022
Pointe Coupee County130Hard1,1681442024
St. Mary County130Hard3,2121432024
Assumption County114Moderately hard360662021
Calcasieu County110Moderately hard2,8254672024
Richland County110Moderately hard6791182023
West Baton Rouge County100Moderately hard9941192024
West Carroll County98Moderately hard373692025
St. Martin County97.2Moderately hard7751542023
St. Landry County96Moderately hard1,4802312024
Rapides County95Moderately hard4,0988272024
Ascension County94Moderately hard7432252022
Acadia County92Moderately hard8711512024
Caddo County91.7Moderately hard2,4194392024
Lafayette County87Moderately hard5351552023
East Carroll County84.8Moderately hard310592022
Concordia County82.1Moderately hard8021102023
St. John the Baptist County78Moderately hard6591652022
Tensas County71Moderately hard316602022
Jefferson Davis County55.7Soft8801762024
Catahoula County52Soft2,2111822024
De Soto County45Soft7232202024
Evangeline County44.2Soft5931822024
Morehouse County44Soft1,0682822025
Webster County36Soft6742352023
St. Tammany County34Soft4,2502822024
Caldwell County33Soft585932024
Sabine County28Soft3641502022
LaSalle County26Soft1,0342102024
Ouachita County26Soft1,6113682024
Union County24.8Soft8731532023
Grant County22Soft1,3662832024
Beauregard County21.8Soft9121522023
Winn County20.9Soft6141452024
Livingston County20Soft1,1821462024
Claiborne County19Soft3911032026
Bienville County18.9Soft7082272022
East Baton Rouge County18Soft2,5375222024
Tangipahoa County18Soft1,5331692024
Allen County15Soft1,1621382024
Lincoln County15Soft2871022023
East Feliciana County14.2Soft311982024
Vernon County14Soft1,4243682024
Jackson County13.2Soft270912024
Washington County13Soft1,1381042024
St. Helena County6Soft92442015
14 additional results from sites without county attribution (not shown).

ZIP codes

ZIP codes in Louisiana

The ZIP codes below are grouped by the Louisiana 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.

St. Bernard County · 500 mg/L · Very hard

7003270043700757008570092

Red River County · 260 mg/L · Very hard

71019†71034

Franklin County · 197 mg/L · Very hard

71219†71230†71243†71295†71336†71378†

Cameron County · 190 mg/L · Very hard

70630†70631†70632†70643†70645†

Orleans County · 190 mg/L · Very hard

701127011370114701157011670117701187011970122701247012570126701277012870129†7013070131701397014870163

Jefferson County · 165 mg/L · Hard

700017000270003700057000670036†700537005670058700627006570067†70072†70094701217012370358

Plaquemines County · 164 mg/L · Hard

70037†7003870040†70041†7005070082†70083†70091†

Terrebonne County · 154 mg/L · Hard

7034470352703537035670359703607036370364703777039570397

Bossier County · 150 mg/L · Hard

71006†7103771051†7106471067†7111071111†71112

Natchitoches County · 149.5 mg/L · Hard

710027106671070†71411†7141471416†71428†71434†71450†71452†71455†71456†7145771468†71469†71497

St. Charles County · 147 mg/L · Hard

70030†7003170039†7004770057†70070†700797008070087†

Iberia County · 143 mg/L · Hard

70513†70528†7054470552†70560†70563

Iberville County · 140 mg/L · Hard

7072170740†70757†70764†7077270776†70780†70788†

St. James County · 140 mg/L · Hard

70052†7007170086†70090†70723†70743†70763†

Vermilion County · 140 mg/L · Hard

70510†70533†70542†70548†70555†70575†

West Feliciana County · 140 mg/L · Hard

70712†70775†70782†70787†

Lafourche County · 132 mg/L · Hard

70301†7031070343†70345†70354†70355†70357†70373†70374†7037570394

Avoyelles County · 130 mg/L · Hard

71320†71322†71323†71327†71331†71333†71339†7134171350†71351†71355†71362†71369†

Madison County · 130 mg/L · Hard

71232†7123371282†

Pointe Coupee County · 130 mg/L · Hard

70715†70732†70736†70747†70749†70752†70753†70755†70756†7075970760†70762†70773†70783†

St. Mary County · 130 mg/L · Hard

7034070342†7039270514†70522†7052370538†

Assumption County · 114 mg/L · Moderately hard

70339†70341†70372†70380†70390†70391†70393†

Calcasieu County · 110 mg/L · Moderately hard

7060170605†70607†7060970611†70615†7062970633†706467064770661†70663†70665†70668†70669

Richland County · 110 mg/L · Moderately hard

71218†71259†71269†71279

West Baton Rouge County · 100 mg/L · Moderately hard

70710707197072970767

West Carroll County · 98 mg/L · Moderately hard

71237†712427125371263†71266†

St. Martin County · 97.2 mg/L · Moderately hard

70517†70519†70582†

St. Landry County · 96 mg/L · Moderately hard

7051270541†705507055170570†70577†70584†70589†70750†71345†71353†71356†71358†

Rapides County · 95 mg/L · Moderately hard

7130171302†71303†71325†71328†7133071346†7135971360†7140571409†71424†71427†7143071433†71447†71466†71472†71485†

Ascension County · 94 mg/L · Moderately hard

70346†70725†70734707377076970774†70778†

Acadia County · 92 mg/L · Moderately hard

70515†70516705257052670531†70534†70535†70537†705437055670559†70578

Caddo County · 91.7 mg/L · Moderately hard

71004†71007†7100971029†71033†71043†71044†71047†71060†7106171069†71082†7110171103711047110571106†71107†711087110971115†7111871119†71129†

Lafayette County · 87 mg/L · Moderately hard

7050170503†70506†70507†70508†70518†70520†70529†7055870583†70592†

East Carroll County · 84.8 mg/L · Moderately hard

71254†71276†71286†

Concordia County · 82.1 mg/L · Moderately hard

71316†71334†71354†71373†

St. John the Baptist County · 78 mg/L · Moderately hard

70049†70051†70068†70076†70084†

Tensas County · 71 mg/L · Moderately hard

71357†71366†71375†

Jefferson Davis County · 55.7 mg/L · Soft

70532†70546†70549†70581†705917064070650

Catahoula County · 52 mg/L · Soft

71326†71340†71343†71368†71401†71425†

De Soto County · 45 mg/L · Soft

71027†71030†71032†71046†71049†71052†71063†71078

Evangeline County · 44.2 mg/L · Soft

70524†70554†70576705807058570586†71367†

Morehouse County · 44 mg/L · Soft

71220†71223†71229†71250†7126171264†

Webster County · 36 mg/L · Soft

710187102171023†71024†7103971055†71071†71072†71073†71075†

St. Tammany County · 34 mg/L · Soft

70420†70431†7043370435†70437†70445†70447†7044870452†70457†704587046070461†7046370464†70471

Caldwell County · 33 mg/L · Soft

7141571418†71435†71441†

Sabine County · 28 mg/L · Soft

71065†71406†71419†71426†71429†71449†71462†71486

LaSalle County · 26 mg/L · Soft

71342†71371†71465†71480†

Ouachita County · 26 mg/L · Soft

712017120271203712097121271225†7129171292†

Union County · 24.8 mg/L · Soft

7122271234†71241†71256†71260†71277†71280†

Grant County · 22 mg/L · Soft

71407†71417†71423†71432†71454†71467†

Beauregard County · 21.8 mg/L · Soft

7063470652†70653†70657†70660†70662†

Winn County · 20.9 mg/L · Soft

71031†71404†714107142271473†71479†71483†

Livingston County · 20 mg/L · Soft

70449†70462†70706†7071170726†70733†70744†70754†70785†70786

Claiborne County · 19 mg/L · Soft

71003†71038†71040†71048†71079†

Bienville County · 18.9 mg/L · Soft

71001†71008†71016†71028†71045†71068†

East Baton Rouge County · 18 mg/L · Soft

7071470739†7077070791†708017080270803708057080670807708087080970810†708117081270813†70814708157081670817†708187081970820†7082570836

Tangipahoa County · 18 mg/L · Soft

704017040270403†7042270436†70442†70443†70444†70446†7045170454†70455†70456†7046570466†

Allen County · 15 mg/L · Soft

70637†70638†70644†70648†70651†70654†70655†70658†71463

Lincoln County · 15 mg/L · Soft

71227†71235†7124571270†7127271275†

East Feliciana County · 14.2 mg/L · Soft

70722†70730†70748†70761†70777†70789

Vernon County · 14 mg/L · Soft

70639†70656†7065971403†71438†71439†71446†71459†71461†71474†71475†

Jackson County · 13.2 mg/L · Soft

71226†71238†7124771251†71268†

Washington County · 13 mg/L · Soft

70426†70427†70438†70450†

St. Helena County · 6 mg/L · Soft

70441†70453†

† 358 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

Louisiana's groundwater measures harder than its surface water — 94 mg/L across 21,326 samples versus 89 across 59,822, about 1.1× harder. Wells draw from groundwater, so well owners in Louisiana tend to see the harder number — 94 mg/L, moderately hard. Groundwater readings there run 4 to 550 mg/L across the middle 80% of samples. The comparison draws on 10,102 groundwater and 2,278 surface-water monitoring sites; 2,806 readings above 2,000 mg/L were logged but held out of the medians as outliers.

Groundwater (wells)

94 mg/L as CaCO₃ · 21,326 results at 10,102 stations.

Surface water (rivers, lakes)

89 mg/L as CaCO₃ · 59,822 results at 2,278 stations.

Groundwater measures about 1.1× harder than surface water here.

Chemistry

Water chemistry in Louisiana

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

TDS

185 mg/L · n=25,434

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

pH

7.4 pH · n=18,362

pH 7.4 — within the EPA secondary range of 6.5–8.5, on the alkaline side.

Alkalinity

59.1 mg/L as CaCO3 · n=39,222

59.1 mg/L — modest buffering capacity.

Calcium : Magnesium

20.9 : 7.2 mg/L ≈ 2.9 : 1 · n=6,923

Calcium is about 64% of Louisiana's hardness (20.9 mg/L Ca to 7.2 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 Louisiana

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

  • Alluvial aquifers — median 500 mg/L across 4,232 samples at 625 sites: very hard.
  • Mississippi River Valley alluvial aquifer — median 260 mg/L across 1,947 samples at 1,122 sites: very hard.
  • Coastal lowlands aquifer system — median 41 mg/L across 10,618 samples at 5,376 sites: soft.

Together these systems account for 16,797 measured samples at 7,123 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

1900s2020s137

Louisiana's decade median moved from 110 mg/L in the 1900s to 80 in the 2020s. Over the series, the decade median peaked at 137 mg/L in the 1990s and bottomed at 42 in the 1930s. Decade medians reflect where and what agencies sampled in each era, not just changes in the water itself.

Scale

Where Louisiana sits on the scale

On the USGS scale, Louisiana's 90 mg/L is moderately hard — 5.3 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 gpg90 mg/L — Moderately hard
Harder than 37% of the 2,977 measured county medians.

Questions

Frequently asked questions

Is Louisiana's water hard?
Louisiana's median hardness is 90 mg/L as CaCO₃, "moderately hard" on the USGS scale and below the national county median of 140 mg/L.
Which county in Louisiana has the hardest water?
St. Bernard County, with a median of 500 mg/L as CaCO₃ across 1,325 measurements.
Is well water harder than city water in Louisiana?
Groundwater measures harder here — about 1.1× the surface water — so wells tend to run harder (groundwater 94 vs surface water 89 mg/L).
How do I find my exact hardness in Louisiana?
Search your ZIP on the lookup tool, read your utility's Consumer Confidence Report, or test at home with a kit.
Is Louisiana's water harder than the national average?
No. Louisiana's median of 90 mg/L is below the national county median of 140 mg/L; it ranks #27 of the 50 states and D.C.

Compare

States with similar hardness

Two states measure closest to Louisiana's 90 mg/L: Pennsylvania at 83 mg/L and Tennessee at 82.9 mg/L. Louisiana measures harder than 48% 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 — 81,193 Louisiana measurements. Data last verified . Methodology.

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