Why Water Hardness Matters for Your Home
Water hardness is determined by how much dissolved calcium and magnesium a water supply contains, measured in milligrams per litre (mg/L) of calcium carbonate. The higher the number, the harder the water — and the more impact it has on your appliances, pipes, skin, and cleaning products.
In the UK, areas like London, Brighton, and Oxford typically see hardness above 250 mg/L — classified as very hard. Scotland and the South West tend to have much softer water below 60 mg/L. This variation is driven by local geology: water passing through chalk and limestone picks up more minerals than water flowing over granite.
Practical effects of hard water include faster limescale build-up in kettles and boilers, the need for more detergent in dishwashers and washing machines, reduced heating efficiency, and for some people, drier skin and hair. Our tools help you understand what your local level means and what — if anything — you should do about it.