What You Need to Know About Hardness in Drinking Water

Water described as “hard” contains high amounts of calcium and magnesium, which are naturally found in the Earth's crust. Total hardness is the sum of the calcium and magnesium concentrations, both expressed as calcium carbonate, in milligrams per liter (mg/L). You can determine your water’s hardness based on these concentrations of calcium carbonate:

  • Below 75 mg/L - is generally considered soft

  • 76 to 150 mg/L - moderately hard

  • 151 to 300 mg/L - hard

  • More than 300 mg/ - very hard

Health concerns: Is hard water or an abundance of calcium harmful to my health?

Hard water (high in calcium and magnesium) is not a health risk. The calcium and magnesium in water can contribute positively to your overall mineral intake. An 8-ounce glass of moderately hard water contains about 50 to 75 mg of calcium. In comparison, an 8-ounce glass of milk provides about 300 mg of calcium.

Hard water can also be a nuisance at home because of:

  • Gray staining of washed clothes
  • Scum on wash and bath water after using soap or detergent
  • Reduced lathering of soaps
  • Buildup of scale on heating elements and boilers
  • Reduced water flow in hot water distribution pipes due to scale buildup
  • Accumulation of whitish-gray scale in tea kettles and other containers used to boil water

Hardness minerals can be removed with a water softener, which replaces the calcium and magnesium (and iron, manganese, radium and other positive ions) with sodium. High levels of sodium in drinking water may harm your health.

If you or someone in your household is on a low-salt diet, talk with your health care provider about the level of sodium in your water. The U.S. Environmental Protection Agency recommends no more than 20 mg/L (milligrams per liter) of sodium in drinking water for people restricted to a total sodium intake of 500 mg/day (milligrams per day). If you are concerned about your sodium intake but would like soft water for your appliances and plumbing, you can have your kitchen cold water faucet bypass the water softener.

Source: How does calcium get into my water?

Calcium and magnesium are naturally found in the Earth's crust. When rainwater combines with carbon dioxide from the air, it creates slightly acidic water. As rainwater moves through natural rock formations underground (usually limestone), it can dissolve the calcium and carry it into aquifers that serve as sources of drinking water.

Testing: How do I know if calcium is in my water?

High levels of calcium in drinking water mean you have “hard water.” Hard water can cause laundered clothes to look dingy. Hard water also causes a whitish-gray scale to form on glass shower doors and bathroom and kitchen fixtures.

The Health Department recommends testing your well or spring for hardness as part of an inorganic chemical test kit every five years. You can order the inorganic chemical test (Kit C) from the Health Department Laboratory, or you can use another certified drinking water lab to test for hardness.

Test results: Is my result a problem?

There is no health standard for hardness in water. Hardness levels greater than 150 mg/L are considered hard water. Hard water is considered a nuisance and not a health issue.

Note: If your water is hard, it can reduce the efficiency of any type of water treatment, such as ultraviolet (UV) light treatment or a reverse osmosis (RO) system. You may need to also consider softening your water before installing water treatment systems.

Need help understanding your drinking water test results? Find out how to read your results

Treatment options: Can I remove or lower the levels of calcium in my water?

The most common way to remove hardness from drinking water is to install a water softener. For every milligram of hardness that is removed, 0.46 milligrams of sodium will be added to the water. Potassium chloride can be used as an alternative to sodium chloride, but potassium chloride is not as efficient at removing hardness.

Consider the location of nearby water sources before disposing of the wastewater produced by a water softener. The wastewater could contaminate nearby wells with sodium, so underground disposal should take place downhill and as far as possible from the well.

Hard water can cause scale on reverse osmosis treatment membranes and ultraviolet light bulbs, which can make treatment less effective. A water softener can resolve this problem.

The membrane manufacturers will often specify what the maximum hardness concentration can be, but the industry rule of thumb is that hardness should not exceed 120 to 170 mg/L (7 to 10 grains per gallon).

Learn more about water softeners

Financial assistance: Is there funding available to help me pay for my water system or treatment?

Vermont Wastewater and Potable Water Revolving Loan Fund

This program, also known as the On-Site Loan Program, is available to certain Vermont residents for the repair or replacement of failed water supply and on-site wastewater systems. The On-Site Loan Program is funded and administered by the Agency of Natural Resources, Department of Environmental Conservation with loan underwriting and servicing provided by the Opportunities Credit Union in Winooski. Your drinking water supply has to be a failed system and you must be living in the residence on a year-round basis to be eligible. The family income cannot exceed 200% of the state median household income. For more information about eligibility and how to apply, call the On-Site Loan Program at 802-461-6051.

The NeighborWorks Alliance of Vermont

The NeighborWorks Alliance is made up of five local organizations offering full affordable housing services for income-eligible individuals. You may qualify for help from this program if you need money to install a water treatment system, drill a well, or repair or replace your septic system. For more information on eligibility, contact the local NeighborWorks Group in your region.

Single Family Housing Repair Loans and Grants

This program offers loans and grants to existing homeowners for well construction, repair and sealing. It's administered by the Rural Development office of the U.S. Department of Agriculture. The program is for low-income families who live in a rural area or a community with a population of 25,000 or less. The family income cannot exceed 50% of the median county income. Individuals who are 62 years of age or older may qualify for a grant or a combination of a loan and a grant. Younger applicants are eligible only for loans.

Burlington, South Burlington, Essex Junction, Winooski and parts of Colchester are ineligible for the program. Even if your property is in an eligible area, your eligibility is still subject to income limits. For more information or to find out if your property is in an eligible area, call the USDA Rural Development Office at 802-828-6022.

Low-interest Loans for Individual Household Wells and Septic Systems

The Southeast Rural Community Assistance Project (SECAP) has partnered with RCAP Solutions (North Eastern Rural Community Assistance Partnership) to provide low-interest loans to construct, refurbish or replace individual water well systems and septic systems for eligible homeowners. Here are the requirements:

• Your residence must be in an eligible rural area, town, or community (defined as geographic area with 50,000 residents or less) in the RCAP Solutions service area of: Maine, New Hampshire, Vermont, Massachusetts, Connecticut, Pennsylvania, Rhode Island, New York, New Jersey, Puerto Rico and the U.S. Virgin Islands. 

• You must own (or provide recorded Lifetime Rights) and occupy the home being improved. 

• Your household limit is under the state median income limit.

• New home construction and community water systems are not eligible. 

Learn more about the loan program and fill out the form.

Please contact SERCAP staff for further information by phone at 540-345-1184 ext. 159 or email [email protected]

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