About your water

'Hard' water is water with a lot of calcium in it – the more it contains, the harder the water is.

This doesn't affect drinking water quality.

When rain falls it contains no calcium, but as it flows over the land and filters through rocks, it dissolves minerals and becomes harder.

How hard water is depends on local geology – water hardness varies widely throughout the UK.

Most of the water we supply is hard, as it comes from underground chalk aquifers with high levels of calcium.

We don't soften water before it reaches your taps – there's no UK or European standard for the hardness of drinking water.

• Soft water contains less than 100mg of calcium carbonate per litre.
• Moderately hard water contains between 100 and 200mg of calcium carbonate per litre.
• Hard water contains between 200 and 300mg of calcium carbonate per litre.
• Very hard water contains more than 300mg of calcium carbonate per litre.

When you heat hard water, a harmless scum appears (limescale) and sometimes attaches itself to appliances (you’ll no doubt have seen it at the bottom of your kettle, or even floating in your tea!).

You’ll need to clean your kettle regularly to stop scum forming.

You can get scum in boilers, on heating elements and in hot water pipes. One way of keeping it at bay is to keep the temperature of the water running through these systems below 60 degrees.

You can avoid hard water completely by fitting a household water softener, as long as it meets the requirements of Water Supply (Water Fittings) Regulations 1999. Here’s more about water regulations.

If you do get one fitted, you’ll need a separate tap for water that hasn’t been softened, to use for cooking and drinking. That’s because softeners can significantly raise the levels of sodium in your body.