Understanding water hardness

Water hardness is the measure of the concentration of calcium and magnesium salts in your water - two of the essential minerals that your body needs!

Checking water hardness

It's worth knowing how hard your water is as the operating instructions for some domestic appliances, particularly dishwashing machines, refer to it.

Domestic appliance manufacturers describe water hardness in a variety of different ways. The hardness conversion factors below will help you to understand what it all means.

Water hardness conversion

Description	Hardness in mg/l as calcium	Hardness in mg/l as calcium carbonate
Soft	0 - 20	0 - 50
Moderately soft	20 - 40	50 - 100
Slightly hard	40 - 60	100 - 150
Moderately hard	60 - 80	150 - 200
Hard	80 - 120	200 - 300
Very hard	Over 120	Over 300

Hardness may be expressed differently depending on where in the world your appliance was manufactured.

Does water hardness have any health benefit?

There is some evidence of lower cardiovascular disease rates associated with hard water areas than in areas where the water supply is soft.

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.

There is no known health risk associated with hardness.

Why isn't all water the same?

Water hardness can differ across our region as it depends on the soil and rocks from where your water is taken.  For example where water has been abstracted from chalk or limestone aquifers it will tend to be harder (mainly in the east); on the other hand water from moorlands tends to be softer (mainly in the west).

Our unique Yorkshire Grid means that we can transport water around the region to where it's needed most - for instance, if we're carrying our work or there's low rainfall in a area.  This can mean that your water hardness is not always the same as the source may vary.

What is the scale in your kettle?

Hardness due to calcium bicarbonate is destroyed by boiling and is therefore sometimes referred to as "temporary hardness". Boiling changes it to insoluble carbonate, which is seen as a scale in kettles or a slight film on hot drinks.  There's no need to worry though as it's completely harmless. 

Hardness due to calcium and magnesium sulphates is not affected by boiling and is sometimes referred to as "permanent hardness".

Seven ways to a better brew:

1. Clean your kettle regularly (refer to the manufacturers instructions).  De-scaling solutions are available from most hardware shops and chemists, but may not be needed if your water is mostly soft.
2. Using a jug filter can partially soften water and eliminate floating 'scum'. Please check that the replaceable cartridge is designed for softening and always follow the manufacturer's instructions.
3. Always make your tea in a teapot and not in a mug or cup
4. Use a kettle and teapot with a spout at the bottom
5. Try adding milk to your cup first.  Full cream milk produces more film than semi-skimmed milk.
6. Don't let your tea stew as this will result in more scum.
7. Try using a tea strainer, even if you use tea bags.

Other useful advice

Dishwashers

Harmless limescale is formed when hard water is heated. Most modern dishwashers have built-in water softeners that prevent white film or spots forming on glassware and crockery. Water softening products can be added to older machines. Make sure you top up your dishwasher with salt and rinse aid when they need it. If you've a problem with your dishwasher, please check the manufacturer's instructions for how to adjust the setting of the softener to suit the water hardness.

Water softeners

We're responsible for supplying clean, wholesome water. Our customers, both domestic and industrial, may want to alter the hardness of their water; some would want less, but some need a high level of hardness. We therefore leave it up to you to decide whether artificial softening is the right choice.

You may choose to install softening equipment at home. This is quite practicable, provided it's done in accordance with the Water Supply (Water Fittings) Regulations 1999 (formerly known as the Water Byelaws), but we advise customers not to soften the supply to the taps from which drinking water is drawn

There are efficient softening devices available for domestic installation from reputable companies.   However, it's essential to have at least one tap supplying unsoftened water for cooking and drinking, because softeners can significantly increase the level of sodium in the water.

We can't advise on whether or not a water softener can be fitted. For advice on the installation of filters, softeners and other devices you might find  British Water's website useful.

Water conditioners

Water conditioners are designed to help overcome the problems of hard water by preventing hardness deposits from sticking to heating elements and pipes.

Unlike water softeners, these devices don't chemically remove the hardness from the water. Although you may benefit from the installation of water conditioners, they haven't worked everywhere and we don't recommend their use.

Removing scale from hot water taps and shower heads

Limescale can build up in taps and shower heads fed from your hot water system.  Taps and shower heads can be cleaned using a descaler, available from hardware stores, or by carefully using either vinegar or a citric acid solution and rinsing fully afterwards.

Checking the colour of your scale

Pure scale from hard water is white in colour, but scale can become coloured by traces of other minerals or metals. For instance, traces of copper in plumbing can turn it grey, green or blue while traces of rust from pipework can turn it brown or black.

Water hardness experiment

To confirm that particles are due to hardness, you can test them safely with either vinegar or citric acid.  Try the experiment below:

1. Carefully place some of the particles in a glass.
2. Slowly add a few drops of ordinary vinegar or a solution of half a teaspoon of citric acid dissolved in half a cupful of water.
3. The hardness scale should fizz slightly, giving off bubbles of harmless carbon dioxide gas. This confirms that the particles are naturally occurring hardness minerals. The liquid in the glass may change colour if metals such as copper are dissolved as well.