What is a water softener? A device for removing the hardness or calcium & magnesium salts from your water supply, as opposed to a limescale inhibitor which alters the characteristics of the salts present.

The process works by passing the incoming water though an “ion exchange resin” whereby the calcium and magnesium salts are removed from the water and replaced with sodium thus removing the hardness. For every 100mg/l (parts per million) of calcium carbonate hardness that is removed from water, 46 mg/l of sodium is added.

How does Ion Exchange work?

In this application, ion-exchange resins are used to replace the magnesium and calcium ions found in hard water with sodium ions. When the resin is fresh, it contains sodium ions at its active sites.

When in contact with a solution containing magnesium and calcium ions (but a low concentration of sodium ions), the magnesium and calcium ions preferentially migrate out of solution to the active sites on the resin, being replaced in solution by sodium ions. This process reaches equilibrium with a much lower concentration of magnesium and calcium ions in solution than was started with.

The resin can be recharged by washing it with a solution containing a high concentration of sodium ions (e.g. it has large amounts of common salt (NaCl) dissolved in it). The calcium and magnesium ions migrate off the resin, being replaced by sodium ions from the solution until a new equilibrium is reached. The salt is used to recharge an ion-exchange resin which itself is used to soften the water.

A water softener is generally around the size of a large tower computer and is usually installed in the sink unit and either electrically operated to provide time-clock regeneration or non electrical, using water flow to provide demand initiated regeneration. Electrical usage is minimal, around the same as an electric clock.

An on- going cost is the salt which has to be replenished at regular intervals. This is available in granular, tablet & block form, the granular being the cheapest. The amount of salt used depends on usage.

A water softener is the only way to remove the calcium and magnesium salts from your water supply. As the softened water contains neither of these salts, the limescale that has built up in your pipes, heat exchanger and cylinder will now start to transfer back to the water and over a period of time will become limescale free, the time depends on how badly scaled the existing system is, but a rough guide would be around 6 months to clean a heat exchanger and around 2 years to clean the whole water system.

What Are The Benefits of Softened Water?

A water softener will improve the efficiency and lifespan of appliances such as washing machines, dishwashers, kettles, combi boilers, showers and hot water cylinders.

Energy savings are made because of increased efficiency in energy source to water transfer. Remember around a 10-11% decrease in efficiency every year due to limescale build up. No tide marks or scum in the bath, shower heads don’t get blocked, no limescale deposits on the sink and taps. Some excema suffers have noticed improvements to their condition when bathing or showering with softened water. It’s easier to get a lather with soap, less detergent and cleaning products needed.

Regarding installation, this is a relatively straightforward procedure, making sure that the Water Supply (Water Fittings) Regulations, 1999,  is followed. The British Water Code of Practice recommends that a mains water tap should be fitted, to provide an unsoftened drinking water supply. This can be in the form of a Tri-flow tap, or a separate tap fitted next to the existing kitchen tap.

It is particularly important that unsoftened water is used for mixing baby formula as the powdered milk already contains sodium and babies have under developed kidneys which are susceptible to high sodium levels. Also, anyone on a low sodium diet, or with high blood pressure should avoid drinking softened water due to the sodium content.

Water Softeners & Septic Tanks

The amount of sodium in softened water has no detrimental effect on the biological workings of a septic tank, but the brine backwash which regenerates the ion exchange resin block should not be discharged into a septic tank.

The concentrated brine can affect the flora of the septic tank and lead to problems with the formation of sludge and stratification of the waste. If you have a septic tank then the brine discharge should be run to the same land drain as the rainwater discharges which will rapidly dilute it.

The cost of a water softener can be anywhere between around £400-£1200 + installation, dependent upon a site survey and customer requirements. Lifespan is 15-20 years with minimal maintenance. Running costs are the cost of salt, but these are offset by the energy savings made.




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