The water hardness indicates how many alkaline earth metals (especially calcium and magnesium) are present in the water. The higher the water hardness, the more of these hardeners are in the water. The Detergent Act regulates the classification of the hardness ranges. A distinction is made between three hardness ranges:
- Soft water hardness range: Water hardness less than 8.4° dH
- Medium water hardness range: Water hardness between 8.5° dH and 14.6° dH
- Hard water hardness range: Water hardness higher than 14.6° dH
High water hardness is a problem, especially in the home. Limescale deposits and higher detergent consumption occur. In addition, the taste of the coffee changes when the water is very hard, since the coffee aromas cannot unfold. In areas with high water hardness, the use of a central water softener in the house is recommended to avoid hard water problems.