These are chemicals which help to control water hardness. There are two types, precipitating and non-precipitating.

Precipitating water softeners include washing soda and borax. These products form an insoluble precipitate with calcium and magnesium ions. The mineral ions then cannot interfere with cleaning efficiency, but the precipitate makes water cloudy and can build up on surfaces. Precipitating water softeners increase alkalinity of the cleaning solution and this may damage skin and other materials being cleaned.

Non-precipitating water softeners use complex phosphates to sequester calcium and magnesium ions. There is no precipitate to form deposits and alkalinity is not increased. If used in enough quantity, non-precipitating water softeners will help dissolve soap curd for a period of time.

Mechanical water softening units can be permanently installed into the plumbing system to continuously remove calcium and magnesium.

Water softeners operate on the ion exchange process. In this process, water passes through a media bed, usually sulfonated polystyrene beads. The beads are supersaturated with sodium. The ion exchange process takes place as hard water passes through the softening material. The hardness minerals attach themselves to the resin beads while sodium on the resin beads is released simultaneously into the water.

When the resin becomes saturated with calcium and magnesium, it must be recharged. The recharging is done by passing a salt (brine) solution through the resin. The sodium replaces the calcium and magnesium which are discharged in the waste water.

Hard water treated with an ion exchange water softener has sodium added. According to the Water Quality Association (WQA), the ion exchange softening process adds sodium at the rate of about 8 mg/liter for each grain of hardness removed per gallon of water.

For example, if the water has a hardness of 10 grains per gallon, it will contain about 80 mg/liter of sodium after being softened in an ion exchange water softener if all hardness minerals are removed.

Because of the sodium content of softened water, some individuals may be advised by their physician, not to install water softeners, to soften only hot water or to bypass the water softener with a cold water line to provide unsoftened water for drinking and cooking; usually to a separate faucet at the kitchen sink.

Mechanically softened water is not recommended for watering plants, lawns, and gardens due to its sodium content.

It may be useful to invest in a water filter for your home to make sure that your drinking water is clean and free from contaminants. There are different forms of water filters available today, all useful as a water softening treatment:

Granulated, activated carbon water filters:
These are portable filters that are found in water jugs. They are the most simplest type of filter and removes contaminants such as chlorine, large particles and parasites. They are available at most kitchenware stores and are reasonably cheap if you have a low budget. However, they have a short filter life and don't filter out many chemicals and bacteria.

Carbon block, activated carbon water filters:
These types of filters are generally built-in to the water supply in your home. These filters are more expensive than granulated types, but they do give better filtration and do not need to be replaced as often.

Ceramic carbon water filters:
This type of filter is comprised of a ceramic part and a carbon part, this gives it an ability to filter out a broad range of contaminants from the water supply. Some are infused with silver, as this is a good antibiotic and reduces the number of micro-organisms present. These filters are good value for money. They are built-in to the home water supply and need to be replaced about every 12 months in the average household.

Reverse osmosis water filters:
These filters are often considered the best form of water filtration available today. The water is passed through a semi-permeable membrane, which filters out almost every contaminant. They are more expensive than other types of filters but have reasonably low running costs, effective filtration and can be used to filter water to the whole house.

Combination Systems:
This filter has become available in recent years and are seen as an alternative to reverse osmosis systems. They have a number of different filters, and each filtration process removes different contaminants.

Alkaline Water Machines:
This system not only filters your drinking water but it makes it more alkaline. It is a good system for those with environmental illnesses where there is too much acid in the body. It has effective filtration but it can be expensive and it wastes a lot of water during the filtration process.

Electromagnetic water conditioners are a relatively new invention. The idea is that by passing water through a magnetic field, the calcium and magnesium ion's are altered in such a way that they loose their ability to cause scale.

This has a number of benefits; although the water is not technically soft, it has the useful properties of soft water, that is, it won't cause limescale in your pipes thus increasing heating efficiency and lengthening the lifespan of any clothes washed in the conditioned water.

Calcium is an important dietary element, so the fact that conditioned water still retains its calcium content is an added benefit.