Hardness in water is caused by dissolved calcium and magnesium, primarily the result of dissolved limestone or minerals from the soil.  High hardness can cause lime build up (scaling) in pipes and water heaters.  It also reacts with soap to form a "scum", decreasing the cleaning ability of the soap and increasing bathtub ring and graying of white laundry.  Water that is naturally too soft may be corrosive.

Acceptable results:  Hard water benefits health. However, values near 150 ppm are ideal.

Sources;  Primarily dissolved limestone or minerals from the soil and rock materials.

Recommended testing:  Annually, along with conductivity.