What usually causes hardness in water?

Hardness in water is primarily caused by the presence of calcium and magnesium ions. These minerals typically enter water supplies through the dissolution of limestone, gypsum, and other geological formations containing calcium and magnesium compounds. When water passes over or through these materials, it can pick up these ions, leading to increased hardness.

Hard water often poses challenges in various applications, including scaling in pipes and water heaters, which can affect plumbing systems and the efficiency of appliances. It can also impact soap and detergent effectiveness, requiring more to achieve the desired results. Understanding the role of calcium and magnesium in water hardness is essential for water treatment processes aimed at softening the water to improve quality and usability for different purposes.

In contrast, other minerals and compounds listed may affect water quality but are not responsible for hardness. Iron and manganese can cause staining and affect taste, while chlorine is primarily used for disinfection, and sulfates can contribute to taste and corrosion issues, but none of these contribute to hardness like calcium and magnesium do.