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Hard water, state by state.

Hardness for 6,993 utilities serving 115 million people as they report it, from states’ own results and utilities’ own reports. Hardness is the calcium and magnesium in water; EPA sets no limit for it.

The short answer

Among utilities serving 100,000 people or more, the hardest water here is City of Garden Grove’s in Garden Grove, CA: very hard, typically 331 mg/L (19.4 grains per gallon). The softest is Greenville Water’s in Greenville, SC: soft, an average of 5.7 mg/L (0.3 grains per gallon).

Few states make utilities report hardness. Most of these figures are from California, Washington, Wisconsin, Kansas, Illinois, Massachusetts and a few more states; elsewhere, only some large utilities, from their own reports.

The hardest tap water

The 10 hardest among utilities serving 100,000 people or more whose water is in one band, by its typical figure. Each figure is from the utility’s own report or was checked against it.

The hardest tap water among large utilities, hardest first
UtilityBased inServesHardness, mg/LGrains per gallon
City of Garden GroveGarden Grove, CA174,22633119.4
Burbank - City, Water Dept.Burbank, CA106,14633019.3
Citizens Water - IndianapolisIndianapolis, IN880,34531718.5
Great Oaks WC IncSan Jose, CA112,58230517.8
Las Vegas Valley Water DistrictLas Vegas, NV1,539,27728016.4
City of Corpus ChristiCorpus Christi, TX317,24723613.8
Pinellas County UtilitiesClearwater, FL506,35321712.7
City of Tampa Water DepartmentTampa, FL733,88621112.3
Sweetwater AuthorityChula Vista, CA184,91519311.3
West Jordan City Water SystemWest Jordan, UT117,02518310.7

The softest tap water

The 10 softest among the same utilities.

The softest tap water among large utilities, softest first
UtilityBased inServesHardness, mg/LGrains per gallon
Greenville WaterGreenville, SC426,0575.70.3
City of Winston - SalemClemmons, NC391,900181
City of Bellingham - Water DivisionBellingham, WA141,127201.2
City of RaleighRaleigh, NC650,000251.5
Seattle Public UtilitiesSeattle, WA1,161,961261.5
Charlotte WaterCharlotte, NC1,206,285321.9
New York City SystemNew York (C), NY8,271,000321.9
City of ColumbiaColumbia, SC354,068362.1
Aquarion - Eastern Fairfield CountyRedding, CT351,756513
City of OlympiaOlympia, WA126,966523

Not ranked: 104 large utilities whose water falls in more than one band, such as Los Angeles - City, Dept. of Water & Power (94 to 544 mg/L), Washington Suburban Sanitary Commission (70 to 154 mg/L) and City of Phoenix (172 to 302 mg/L).

Also not ranked: 46 large utilities whose state figure hasn’t yet been checked against its own report, such as Ventura Water Department (517 mg/L), City of Santa Maria Utilities Department (500 mg/L) and California Water Service Co. - Herm/Redo (415 mg/L). A state’s results can miss what reaches the tap: West Jordan’s covered wells that supply 7% of its water.

Each utility is on its state’s page with its figure or range.

By state

States whose own results cover enough of their utilities for a page, each utility grouped by band.

Other states

Utilities in states with too few measured for a page of their own, most from their own water quality reports.

Utilities with hardness in other states, by state
UtilityBased inServesHardness, mg/LGrains per gallon
City of PhoenixPhoenix, AZ1,695,000172 to 30210.1 to 17.7
City of MesaMesa, AZ466,000205 to 27412 to 16
Aquarion - Eastern Fairfield CountyRedding, CT351,756513
D.C. Water and Sewer AuthorityWashington, DC632,3231398.1
Citizens Water - IndianapolisIndianapolis, IN880,34531718.5
City of DetroitDetroit, MI633,2181076.3
MinneapolisMinneapolis, MN425,300945.5
Saint Paul Regional Water ServicesSt. Paul, MN392,52989 to 1075.2 to 6.3
Charlotte WaterCharlotte, NC1,206,285321.9
City of RaleighRaleigh, NC650,000251.5
City of Winston - SalemClemmons, NC391,900181
Metropolitan Utilities DistrictOmaha, NE660,0001549
City of North PlatteNorth Platte, NE25,0001629.5
Passaic Valley Water CommissionLittle Falls Twp., NJ310,48342 to 2422.5 to 14.2
Kirtland Air Force BaseAlbuquerque, NM22,5001207
Dona Ana MdwcaDona Ana, NM16,98717810.4
Las Vegas Valley Water DistrictLas Vegas, NV1,539,27728016.4
Bristow Municipal AuthorityBristow, OK3,70023613.8
Portland Water BureauPortland, OR666,2007 to 800.4 to 4.7
Greenville WaterGreenville, SC426,0575.70.3
City of ColumbiaColumbia, SC354,068362.1
Charleston Water SystemCharleston, SC278,771543.2
Metro Water ServicesNashville, TN789,96989 to 1285.2 to 7.5
Memphis Light, Gas, & WaterMemphis, TN659,50014 to 1500.8 to 8.8
City of Austin Water & WastewaterAustin, TX1,115,323935.4
City of Corpus ChristiCorpus Christi, TX317,24723613.8
City of Virginia BeachVirginia Beach City, VA437,994563.3
City of Newport NewsNewport News City, VA407,300694
Burlington Dept Public Works Water DivBurlington, VT42,000663.9
Barre City Water SystemBarre City, VT14,000673.9
Springfield Water DeptSpringfield, VT9,80066 to 1493.9 to 8.7
Town of JacksonJackson, WY24,760129 to 2917.5 to 17
City of Rawlins Water SupplyRawlins, WY9,00617410.2
City of DouglasDouglas, WY6,400174 to 23310.2 to 13.6
City of BuffaloBuffalo, WY4,419372.2

What the numbers mean

The U.S. Geological Survey’s bands. Softener makers often give hardness in grains per gallon, at 17.1 mg/L to the grain.

Hardness bands in mg/L and grains per gallon
Bandmg/L as calcium carbonateGrains per gallon
Soft0 to 600 to 3.5
Moderately hard61 to 1203.6 to 7
Hard121 to 1807.1 to 10.5
Very hardAbove 180Above 10.5

Sources: Alabama Department of Environmental Management, Drinking Water Branch (read Oct. 17, 2026); California State Water Resources Control Board, Division of Drinking Water (read Oct. 10, 2026); Colorado Department of Public Health and Environment, Water Quality Control Division (read Oct. 17, 2026); Delaware Division of Public Health, Office of Drinking Water (read Oct. 17, 2026); Florida Department of Environmental Protection, Drinking Water Program (read Oct. 10, 2026); Illinois Environmental Protection Agency, Bureau of Water (read Oct. 17, 2026); Iowa Department of Natural Resources, Water Supply Programs (read Oct. 10, 2026); Kansas Department of Health and Environment, Public Water Supply Section (read Oct. 18, 2026); Kentucky Division of Water (read Oct. 17, 2026); Maryland Department of the Environment, Water Supply Program (read Oct. 17, 2026); Massachusetts Department of Environmental Protection, Drinking Water Program (read Oct. 10, 2026); Montana Department of Environmental Quality, Public Water Supply (read Oct. 18, 2026); Nebraska Department of Water, Energy, and Environment (read Oct. 17, 2026); New Mexico Environment Department, Drinking Water Bureau (read Oct. 17, 2026); Ohio Environmental Protection Agency, Division of Drinking and Ground Waters (read Oct. 17, 2026); Oklahoma Department of Environmental Quality, Water Quality Division (read Oct. 17, 2026); Pennsylvania Department of Environmental Protection, Drinking Water Reporting System (read Oct. 17, 2026); Utah Department of Environmental Quality, Division of Drinking Water (read Oct. 10, 2026); Vermont Department of Environmental Conservation, Drinking Water and Groundwater Protection Division (read Oct. 17, 2026); Washington State Department of Health, Office of Drinking Water (read Oct. 10, 2026); Wisconsin Department of Natural Resources, Drinking Water Program (read Oct. 10, 2026); U.S. EPA Region 8, Drinking Water Program for Wyoming (read Oct. 17, 2026); and 51 utilities’ own water quality reports, read by hand, each named on its utility’s page.

A state’s figure for a utility is the median of its sampling points, typical where every point falls in one band. Where a state samples each well before treatment and the utility runs a desalter or softening plant, the state’s figure is left out, since it can’t say what reaches the tap. People served is what each utility reports; where one sells water to another, the same people can be counted twice. How hardness is measured here.

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