Regional Water Hardness in the UK

Around 60 percent of the UK lives in a hard water area. Water is hard across London, the south east, the east and much of central England, and soft across Scotland, Wales, the north west and south west. The cause is geology: rain dissolves calcium from chalk and limestone.

Is my water hard or soft in the UK?

Around 60 percent of people in the UK live in a hard or very hard water area, so for most households the honest answer is hard. The pattern is regional and it follows the rock under your feet. As a quick map in words, water tends to be hard across London, the south east, the east of England and much of central England, and soft across Scotland, Wales, the north west and the south west.

Hardness is measured in milligrams per litre of calcium carbonate, written as mg/L CaCO3. The Drinking Water Inspectorate, the body that regulates drinking water quality in England and Wales, treats water up to 100 mg/L as soft, 100 to 150 as slightly hard, 150 to 200 as moderately hard, 200 to 300 as hard, and more than 300 as very hard. A fuller version of the same scale splits the soft band into soft below 50 and moderately soft from 50 to 100.

Hard water is perfectly safe to drink. What it creates is limescale, the chalky white buildup that collects on kettles, taps, glass and shower fittings, plus the way the calcium in it interacts with soap. Knowing your local figure tells you how much of that to expect.

Why is UK water hard in some places and soft in others?

Water starts soft. Rain is naturally low in minerals. Hardness is picked up on the way down, as that rain soaks through the ground and dissolves whatever the local rock will give up.

Where the ground is chalk or limestone, both made largely of calcium carbonate, the water dissolves calcium and magnesium as it passes through. It reaches your tap carrying those minerals, which is what hard water actually is. The thick chalk and limestone belts that run under the south and east of England are the reason those areas carry some of the hardest water in Europe.

Where the ground is granite, slate or other hard, low solubility rock, very little dissolves. Rain that falls on the granite uplands of Scotland, the mountains and moorland of Wales, the Lake District and Dartmoor runs off almost as pure as it landed, which is why those places stay soft. The British Geological Survey maps this bedrock, and the hardness map of the UK follows the geology map very closely.

Which UK regions have the hardest water?

The hardest water sits in a broad band across the south and east. Thames Water, which supplies London and the Thames Valley, publishes hardness that typically runs from about 250 to 350 mg/L CaCO3, comfortably in the very hard class and among the hardest supplied to any major city in Europe. Anglian Water, covering much of the east of England, is similar, with many chalk fed zones sitting above 300 mg/L.

The south east follows the same chalk geology. Southern Water and South East Water both supply water that is widely hard to very hard, often in the 200 to 320 mg/L range, and much of central England and the Midlands sits in the moderately hard to hard band. If you live anywhere in this arc, expect visible limescale and to see it return quickly after cleaning.

Which UK regions have soft water?

Move to the upland west and north and the picture flips. Scottish Water reports typical hardness of around 10 to 50 mg/L CaCO3, among the softest supplied to any large population in Europe. Welsh Water averages roughly 68 mg/L across Wales, with many upland zones well below that.

In the north west, United Utilities averages about 77 mg/L, sitting between soft and slightly hard. South West Water, covering Devon and Cornwall, runs from the high 20s to around 138 mg/L, soft in most places with a few harder pockets where supplies come from boreholes rather than moorland reservoirs. In these regions soap lathers easily and limescale is a minor concern.

How do I check the exact hardness for my postcode?

Regional figures are a guide, not a guarantee. Hardness can change street by street, because neighbouring areas are sometimes fed from different sources, and a single water company can supply both soft and hard zones. The only way to know your real number is to check your specific postcode.

AQUERIE offers a free UK Water Report. Enter your postcode and it returns your local hardness figure, its classification on the scale above, and what that means for limescale and for your skin and hair. It takes seconds and needs no sign up. If you want the exact number for your address rather than a regional average, start there.

One thing worth knowing: a shower filter does not change how hard your water is. What people in hard water areas use one for is to reduce the chlorine they shower in and to help prevent limescale buildup on the fittings. Checking your postcode first tells you whether you are in an area where that is worth doing.

Signs you live in a hard water area

• White chalky limescale on the kettle, taps and shower screen
• Soap and shampoo that will not lather easily
• Spots and a cloudy film left on glasses and dishes after washing
• Skin that feels tight or dry and hair that feels rough after a shower
• Weaker flow from the shower head as scale collects in the holes