Hardness in Drinking Water

Hardness was originally a measure of the capacity of water to react with soap, where hard water requires more soap to create a lather.

Water described as “hard” contains high amounts of naturally occurring dissolved calcium and magnesium. 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, however, 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.

People who have high blood pressure or are on a sodium-restricted diet should not drink water containing greater than 20 mg/L of sodium without first checking with a health care professional. 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?

Rainwater combines with carbon dioxide from the air, creating slightly acidic water. When that water moves through bedrock containing calcium (usually limestone), the calcium dissolves and can get into groundwater aquifers.

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.

You can test for hardness as part of the inorganic chemical test (Kit C), recommended for private well owners every five years. You can order Kit C by calling the Health Department Laboratory at 802-338-4724 or 800-660-9997 (toll-free in Vermont). You can also use a certified drinking water lab to test for hardness. Search for a certified drinking water lab

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

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.

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

Water Softeners

The most common way to remove hardness from drinking water is to install a water softener, which replaces the calcium and magnesium ions with sodium ions. 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 industry rule of thumb is that hardness should not exceed 120 to 170 mg/L (7 to 10 grains per gallon).

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.