How to Test Water for Hardness

Written by sueanne dolentz
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Hard water is nothing more than water with a high mineral content. It may contain such minerals as magnesium, calcium and other dissolved compounds like sulphates or bicarbonates. Because of the high mineral content, hard water leaves behind deposits that form after the water has evaporated, leaving a less-than-clean feeling on the skin, clogging drains and possibly damaging water heaters. Testing the water in your home for hardness is easy, and no gadgets or outside experts are required.

Skill level:

Things you need

  • Liquid dishwashing detergent

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  1. 1

    Take two separate glasses and fill one with distilled bottled water, the other with water from your tap. Fill them only halfway, and label them appropriately.

  2. 2

    Add 10 drops of liquid dishwashing detergent to each glass. The brand of the detergent is irrelevant, although it must be liquid and not powder.

  3. 3

    Cover the top of the glasses with your hand, and shake each glass until an adequate amount of soap suds have been created.

  4. 4

    Compare the suds level in each glass. If your tap water is hard, it will make less suds than the distilled water.

  5. 5

    Add 10 more drops of detergent to the glass filled with tap water and shake again. If the suds level is now the same in both glasses, your tap water is twice as hard as pure water.

  6. 6

    Repeat the steps until you can determine how hard your tap water may be. For instance, if you add 40 drops of detergent to the tap water, and the suds level is still the same, your tap water is four times as hard as pure water.

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