Water is a very complex fluid. It contains a little bit of  practically everything that it contacts; the air while falling as rain, the earth as it percolates into the ground, the piping as it is transported and all kinds of organic and inorganic matter it may contact in its series of uses. Dissolved minerals in the water that contain an electric charge are called ions. These ions can be either positive or negatively charged with electrons. The positive ions are called cations and the negative ions are called anions. It is these positive cations in the form of calcium, magnesium, iron and manganese that cause the hardness that is associated with water. Removal of these hardness ions via ion exchange is the process used for softening water.