Permanent Hardnes is hardness that can't be taken away by heating. It's normally effected by the existence of calcium and magnesium sulfates and/or chlorides in the water, which begins to be more soluble as the temperture goes up.

In spite the saying, Permanent Hardness could be taken away using a water softener or an ion exchange column, where the calcium and magnesium ions are exchanged with the sodium ions in the column.

Hard water makes sealing, mineral deposites leftovers that are formed after hard water has evaporated. This is limescale. The scale can take away the life of toilet flushing units, clog pipes, coat the insides of coffee and tea pots, and ruin water heaters.

In industrail places, hard water has to be continously monitored to keep away costly break downs in cooling towers, boilers, and other equipent that comes in contact with water. Hardness is comanded by adding chemicals and large - scale softening with zeolite and ion exchange resins.