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Maryland water hardness, by utility.

5 Maryland utilities serving 3.7 million people as they report it, from the state’s own results. Hardness is the calcium and magnesium in water; EPA sets no limit for it.

The short answer

3 utilities serving 2 million people have water in more than one band. Among those in one band, moderately hard water reaches the most people: 1 utility serving 1.6 million.

The largest, Washington Suburban Sanitary Commission, is moderately hard to hard depending on the source, 70 to 154 mg/L (4.1 to 9 grains per gallon).

Moderately hard

61 to 120 mg/L (3.6 to 7 grains per gallon). 1 utility serving 1.6 million people, largest first.

Maryland utilities: moderately hard water
UtilityBased inServesHardness, mg/LGrains per gallon
City of BaltimoreBaltimore1,600,000945.5

Soft

Up to 60 mg/L (3.5 grains per gallon). 1 utility serving 104,567 people, largest first.

Maryland utilities: soft water
UtilityBased inServesHardness, mg/LGrains per gallon
Harford County D.P.W.Abingdon104,567382.2

Varies

Water in more than one band, depending on where or when it was sampled: each is given as its range, softest to hardest, and its report says more. 3 utilities serving 2 million people, largest first.

Maryland utilities: varies water
UtilityBased inServesHardness, mg/LGrains per gallon
Washington Suburban Sanitary CommissionLaurel1,900,00070 to 1544.1 to 9
City of FrederickFrederick54,00018 to 1511 to 8.8
Town of Princess AnnePrincess Anne3,3000.5 to 2790 to 16.3

Source: Maryland Department of the Environment, Water Supply Program, 4 utilities, results from Feb. 13, 2015 to Aug. 25, 2026, read Oct. 17, 2026. Each sampling point is taken at its median; a figure is typical where every point falls in one band.

Also: 1 utility’s own water quality reports, read by hand, each named on the utility’s page.

Bands are the U.S. Geological Survey’s, at 17.1 mg/L to the grain. 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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