Water hardness

Water hardness is the result of naturally occurring calcium and magnesium salts. Water containing small amounts of these salts is said to be soft, whilst hard water contains greater levels.   For further information on the hardness of the water supply in your area, please use the postcode search function provided on this website.

What is water hardness?
There are two types of hardness, temporary and permanent, which depend on the type of salts present.

• Temporary hardness is usually result of dissolved calcium carbonate, which forms the familiar whitish coloured scale seen in kettles.
• Permanent hardness contains the sulphates of calcium and magnesium, which remain soluble even when heated.

Where does hardness come from?
Around 50 per cent of the water used in the Anglian Water region is collected from underground sources. Some rocks have a high chalk content, which dissolves into the water as it seeps through, thus increasing the hardness. These underground sources yield valuable, high quality water because the chalk filters the water and removes any impurities. Water abstracted from rivers and via reservoirs is also generally hard due to this geology.

Hardness varies across different parts of the country; a map of the hardness in the Anglian Water region is shown below: 

How is hardness measured?
To calculate the total hardness of the water, the quantity of calcium and magnesium salts present in the water is found using the following calculation:

[mg/l calcium x (2.497) + mg/l magnesium x (4.188)] x 0.4

This calculation gives the total hardness of the water as calcium in milligrammes per litre, which can be seen on the Detailed Report for the supply zone as Total Hardness (as Ca).  Total hardness can be expressed in a number of different units. Dishwasher manufacturers may use these different units in the instructions for setting salt levels. The table below provides the calculations used to convert Total Hardness (as Ca) to these different units. 

Is it dangerous?
An adequate daily intake of calcium is essential for normal growth and health. Foods such as dairy products, beans, eggs, nuts, cauliflower and spinach contain calcium. The hardness of water has a small but beneficial effect on a healthy diet, and a number of studies have shown that drinking hard water reduces cardiovascular disease.

Has the problem got worse in recent years?
Levels of hardness have generally not increased, but the effects may be more noticeable due to new designs in kettles and the more common use of steam irons.

Stainless steel and plastic kettles do not ‘collect’ scale like old-style kettles and so the scale floats freely in the boiled water. This is part of the reason why scum may be noticed on hot drinks – the freely floating scale reacts with the essential oils in tea and coffee.It is not harmful in any way.

Here are some simple tips to help improve the appearance of your cup of tea:

• Always make your tea in a teapot and not a mug or cup.
• Use a kettle and a teapot with a spout at the bottom.
• Add the milk to your cup first.
• Don’t let the tea stew as this results in more scum.
• Try using a tea strainer even if you use tea bags.

Do I need a domestic water softener?
Anglian Water is responsible for supplying a reliable source of safe, clean, drinking water. Anglian Water does not interfere with the natural hardness of the region’s water, it is left to the customer, either domestic or industrial, to decide whether artificial softening is the right choice for them.

There are efficient softening devices available for domestic installation from reputable companies. Most work by altering the chemical composition of the water. The calcium and magnesium are substituted by sodium.

Anglian Water strongly advises that customers keep at least one mains-fed tap in the property for drinking and cooking purposes. This is particularly important for bottle-fed infants and anyone on a sodium-restricted diet*. In addition, a number of studies show that drinking hard water reduces cardiovascular disease.

* Many water softeners work by exchanging the calcium and magnesium in the water for sodium.

Anglian Water also advises that any water softening devices are installed and operated in strict accordance with the manufacturers instructions.   Further independent advice concerning water softeners and filtration devices can be obtained by contacting British Water at 1 Queen Anne’s Gate, London SW1H 9BT, Telephone Number 0207 957 4554 or by visiting their website at www.britishwater.co.uk