Hard Water and Lime Scale Build Up
The water supplied to our homes is often described as hard or soft. Hard water contains varying amounts of minerals including calcium and magnesium and these are what can lead to a build up of deposits usually called lime scale.
What happens is that when the water is heated, or it is left to stand, the dissolved minerals form a solid residue. Contrary to what you might imagine, heating the water actually makes these minerals less soluble rather than the other way round, hence their significant impact on heating elements. The effects of this can be readily seen in a home in a hard water area. There will be limescale deposits around taps and in the kettle. You will also notice that when washing with hard water, more soap is required to build a lather.
However much of the damage caused by limescale is not so easily seen. Scale builds up in pipes and in appliances such as washing machines. Not only does this reduce water flow along these pipes but it also coats the heating elements and renders them less efficient.
Reducing Lime Scale
There are several methods that can be used to reduce water hardness and the build up of limescale deposits. This will keep sinks and taps free from deposits and prevent damage to appliances with water heating elements such as washing machines and dishwashers. Water softeners actually remove the calcium and magnesium minerals from the water whereas descalers alter the molecular structure of these elements without removing them from the water
These have a pressure chamber which contains resin particles which absorb the calcium and magnesium from the water and replace them with sodium found in common salt. However, the resin gradually becomes saturated with the hard water minerals and this needs to be removed. This process is referred to as backwashing. The resin is flushed through with a saline solution from the salt storage chamber. This releases the calcium and magnesium and replenishes the sodium in the resin. As the salt is used up over time, the storage chamber needs to be regularly topped up.
Base exchange softeners such as these require an annual service to ensure they operating correctly. This should be carried out by a qualified service engineer. Water supplied to these units must be fitted with a single check valve. This prevents backflow which could otherwise contaminate the water supply. You can find detailed information on this in BS 6700.
The downside of this type of water softener is that they increase the level of sodium (salt) in the water and it is therefore recommended that a separate drinking water supply is installed.
Scale reducers are sometimes fitted to water heaters, immersion heaters, boilers and electric showers to reduce the likelihood of damage being caused to these appliances by the build up of limescale. As mentioned earlier, limescale build up on heating elements will make them far less efficient and can reduce their lifespan considerably.
The additives in the cartridge of a scale reducer are designed to change the chemical structure of the salts found in hard water . This change in chemical structure means that the salts will no longer form a chemical bond and the scale deposits will not form. The minerals stay dissolved in the water
You will need to replace the cartridge used for these scale reducers at regular intervals so that they can continue working. Check the manufacturer’s instructions and follow their guidance for this, but it will typically be 12 months or so.
These comprise of a small wire which is coiled around the water pipe and is supplied by a transformer to generate a small electrical charge which creates a magnetic field. This process alters the chemical structure of the minerals so that they no longer have a tendency to bond together. Since the minerals do not bond together, the build up of lime scale deposits no longer take place.
Simpler devices are available which comprise a magnet which is strapped to the pipework by means of a clamp or cable ties. The advantage of these is that no electrical supply is required. Electromagnetic devices tend to be more effective but do require an electrical supply from a socket outlet via a transformer. If you already have a suitable nearby socket outlet there will be no problem installing one of these.