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.

How often recharging occurs depends on the quantity of resin used. One cubic foot of resin allows 32,000 grains of hardness to be removed. If your water is 10 grains per gallon hard, it would mean 3,200 gallons of water can be softened before it is exhausted.

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.

Water filters generally come in two forms. Portable ion exchange water filters, and reverse osmosis water filters. Both are used for "point of use" drinking water, that is, to filter out harmful or unwanted particles before the water is used for human consumption.

Reverse Osmosis works by forcing the water through a semi-permeable membrane, that stops certain particles from passing through. It is also known as Ultra-Filtration by the industry and is state-of-the-art in water treatment technology.

Portable water filters work using a cartridge containing activated carbon and ion exchange resin. The carbon absorbs and helps reduce the levels of chlorine and chlorine compounds, as well as pesticides, colour and other organic substances. This improves taste and appearance. The ion exchange resin works to reduce temporary hardness.

Water filters cost approximately $0.04 (£0.025) / litre to run.

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.

While some people are skeptical this method actually works, we have found one manufacturer who has commisioned a scientific analysis by the University of Bath that concludes that their device does indeed stop the build up of limescale.

Expensive

£1000 ($1400) Unit + Installation

£100 ($140) / Year - Salt + Electricity

£5 ($7) / Year - electricity