Hard water Hardness The hardness of the water depends on the mount of mineral substance—like the calcium and magnesium-- which dissolved by water [1]. When above content is beyond the standard, the water is the hard water. Despite daily ingestion of hard water is not harmful to body, it actually reduces the efficiency of detergent. Injury of fabric washed in hard water also exists. Hard water caused Soap curds will demand the fabric which means it would not be soft and silky as usual [1].