Hard or soft water?

Water hardness is one of the metrics for evaluating domestic water quality. What does hardness mean and what causes it? Is hardness an advantage or a disadvantage? Where can I find out if my tap water is hard or soft?

Hardness refers to the concentrations of certain minerals in water, mainly calcium and magnesium. If the concentrations are high, the water is defined as hard. Tough calcium deposits on the bottoms of saucepans, known as lime scale, are a sign of hard water.

Finnish groundwater is usually soft and contains little calcium carbonate as acidic rocks, such as granite, predominate in the Finnish bedrock. However, in some limestone areas groundwater may be hard or medium hard.

Hard water creates many types of problems, such as lime scale building up in hot water systems and floor drain grates getting blocked. More detergent is needed to wash clothes, and coffee makers must be descaled frequently.

Excessively soft water is not particularly desirable, either, as soft and acidic water corrodes metal water pipes and dissolves harmful substances from them. For this reason, water utilities often add calcium carbonate obtained from limestone to untreated water to reduce its acidity and increase water hardness.

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