How do all those number affect you? Hard water causes two problems:

1.    Dissolved calcium and magnesium precipitate out of hard water as scale, which builds up on the insides of pipes, water heaters, tea kettles, coffee makers and industrial machinery. Scale reduces flow through pipes and is a poor conductor of heat. Eventually, pipes can become completely clogged.
2.    Hard water reduces soap's ability to lather, whether in the shower, sink, dishwasher or washing machine, and reacts with soap to form a sticky scum.

You can combat hard water in various ways, including filtering it by distillation or reverse osmosis, adding a packaged chemical softener such as powdered borax or washing soda (sodium carbonate), or running it through a water softener.

Filtration in sink taps and refrigerator water dispensers improves water's taste, but its steep price tag makes it impractical as a household solution. Packaged chemicals soften water in small batches, such as washing machine loads, but render the water undrinkable, take a toll on clothes, and, in some cases, contain phosphates that harm the environment.

Descaling offers an alternative to water softening. Whereas a water softener removes the problem (minerals in the water), a descaler addresses the damage caused by the problem (scale buildup). You will sometimes see ads for "salt-free water softeners," which are actually descalers, or for magnetic water softeners, which remain unproven and don't change the chemical composition of water, so buyer beware [source: Powell]. Methods for water softening
Water softening methods mainly rely on the removal of Ca2+ and Mg2+ from a solution or the sequestration of these ions, i.e. binding them to a molecule that removes their ability to form scale or interfere with soaps. Removal is achieved by ion exchange and by precipitation methods. Sequestration entails the addition of chemical compounds called sequestration (or chelating) agents.

Since Ca2+ and Mg2+ exist as nonvolatile salts, they can be removed by distilling the water, but distillation is too expensive in most cases (rainwater is soft because it is, in effect, distilled.)

Ion-exchange resin devices

Ion-exchange materials contain sodium ions (Na+) that are readily replaced by hardness ions such as Ca2+ and Mg2+. Ion exchange resins are organic polymers containing anionic functional groups to which the Na+ is bound. Minerals called zeolites also exhibit ion-exchange properties; these minerals are widely used in laundry detergents.

Method of operation

Main article: Ion chromatography

The water to be treated passes through a bed of the resin. Negatively charged resins absorb and bind metal ions, which are positively charged (2RNa(s)+M2+(aq)=R2M(s)+2Na+(aq)(M=Mg or Ca)). The resins initially contain univalent (1+) ions, most commonly sodium, but sometimes also hydrogen (H+) or potassium (K+). Divalent calcium and magnesium ions in the water replace these univalent ions, which are released into the water. The "harder" the water, the more hydrogen, sodium or potassium ions are released from the resin and into the water.
Resins are also available to remove carbonate, bi-carbonate and sulphate ions which are absorbed and hydroxyl ions released from the resin. Both types of resin may be provided in a single water softener. This method is called the ion exchange method.

Regeneration

The resin's capacity is gradually exhausted and eventually it contains only divalent ions (e.g., Mg2+ and Ca2+ for cation exchange resins, and SO42- for anion exchange resins). At this stage, the resin must be regenerated. If a cationic resin is used (to remove calcium and magnesium ions) then regeneration is usually effected by passing a concentrated brine, usually of sodium chloride orpotassium chloride, or hydrochloric acid solution through them. For anionic resins, regeneration typically uses a solution of sodium hydroxide (lye) or potassium hydroxide. The salts used for regeneration are released into the soil or sewer.
In industrial scale water softening plants, the effluent flow from re-generation process can precipitate scale that can interfere with sewerage systems.

With all this in mind, it's clear why water softeners are so popular: They remain the least costly and most effective way to rid your water of troublesome minerals.