Water- hard or soft and limescale

You’ve probably heard people refer to water as being either hard or soft – but what does this mean and how does it affect limescale and your plumbing ?

Hard or soft water ?

The classification of water as hard or soft refers to the acidity of the water and this reflects the impurities that the water has picked up on its way through the environment to your taps.

Chemically,the hardness of water is a measure of the number of hydrogen ions (acidic) and hydroxyl ions (alkaline) present in the water, this is defined as the potential of hydrogen value or pH value.

Pure water has a pH value of 7 (neutral) while soft has a value of less than 6.5 (acidic) and hard water a value greater than 8.5 pH(alkaline)

Water becomes hard if it travels through chalk or limestone and the water absorbs calcium carbonates, sulphates and magnesium.

In the UK, most mains water supplies in the south and east are typically hard,while the north and west are typically soft. It is estimated that hard water is experienced by over 60% of UK homes.

The effects of hard and soft water

Soft water does not contain any dissolved limestone. It is more acidic and aggressive as a solvent, and can soon erode metals, in particular lead where this is used within a plumbing system – so lead should be removed from old plumbing systems especially in soft water areas.

Soft water feels different from hard water and is generally considered more pleasant to wash with; it is much easier to obtain a lather from soap in soft water, but takes more water to rinse the soap away.

Hard water causes the limescale that forms in kettles, around taps and also the scum that forms around the bath and basin after use. Hard water also forms limescale deposits in hot water systems (pipework, tanks and boilers) and appliances(washing machines and dish washers); it can significantly reduce the efficiency in all these areas.

Preventing limescale

Limescale can be prevented by using a water softener or a water conditioner on the mains cold water supply.

Water softeners

water softenerA water softener is a form of filter (but note that not all water filters are water softeners) designed to remove the calcium and magnesium ions from the water supply. Basically, when the water is passed through the filter, the calcium and magnesium are captured. Eventually the filter will stop working and the element will need to be either replaced or regenerated, depending on the type.  

Some(but not all) water softeners use salt (sodium) as part of the filtering process; it is always advised that where such systems are installed, the water should not be considered suitable for drinking (especially by children or babies) and that a separate tap for drinking water should be arranged, this could be achieved by by-passing the water softener to supply a separate tap in the kitchen (this would also minimise the amount of salt in any water used for cooking, making drinks etc).

Water conditioner

A water conditioner does not remove anything from, or add anything to, the water, it just changes the form of the calcium suspended in the water so that it just flows through the system.

There are two basic types of water conditioner.

  1. water magnetic conditionerA magnetic conditioner – the water just passes through a strong magnetic field which changes the form of the calcium. Once installed, the conditioner requires no maintenance or replacement.

  2. Water conditioner kitElectromagnetic conditioner – this works on the same basic principal as a magnetic conditioner but the magnetic field is created by a small electrical current passing through coils fitted around the water pipe. The conditioner requires a mains power supply but no actual maintenance or replacement of parts.