Water hardness is primarily the amount of calcium and magnesium in water, Hardness was originally defined as a measure of the ability of water to react with soap. Hard water requires a considerable amount of soap to produce lather.

Water hardness is commonly found in over 80% of North America. Water hardness in most groundwater is naturally occurring from weathering of limestone, sedimentary rock and calcium-bearing minerals found mostly in deep wells & soils rich in minerals.

Water hardness is very noticeable and visible.

Signs of water hardness

  • Spots and scales on dishes, water glasses, faucets and all household water appliances.
  • Excessive use of soaps and cleaning products.
  • Whites never look white and feel rough.
  • Hair feels heavy and skin feels rough.

Hard water will also scale water pipes and reduce the life of all water appliances.

In Canada water hardness is measured in milligrams per litre (mg/L) of calcium and magnesium minerals. In the U.S hardness is measured in grains per gallon (GPG).

Grains per gallon (GPG) is the most common measurement used.

 The Guidelines for Canadian and U.S Drinking Water Quality Hardness divide hardness into the following categories: 

Hard water measurements

Milligrams per litre (mg/L)

Grains per gallon (GPG)

Soft water

0-17.1 mg/L or less

0-1 GPG

Slightly hard

17.1-51.3 mg/L

1-3 GPG

Moderately hard

51.3-119.7 mg/L

3-7 GPG


119.7-171.0 mg/L

7-10 GPG

Very hard

171.0 and over

10 GPG and over

Health risks

Hard water is mainly an aesthetic concern because of the unpleasant taste that a high concentration of calcium and magnesium ions gives to water. There are no known risk factors in drinking hard water. 



Hard water can be treated using a water softener.


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