UK Water Hardness by Supplier

Yes, Thames Water tap water is hard to very hard across virtually its entire operational network, averaging 275 PPM (19.3° Clark). Rain filtering through the porous Cretaceous chalk of the Chilterns and North Downs dissolves heavy concentrations of calcium and magnesium carbonate.

Severn Trent spans a dramatic hydrogeological divide: Birmingham and the Black Country receive naturally soft water (40–60 PPM) piped 73 miles from Wales, whereas Nottingham, Leicester, and Derby receive hard water (220–290 PPM) from lowland rivers and sandstone aquifers.

Yes, Anglian Water supplies some of the hardest drinking water in the British Isles, averaging 310 PPM and frequently exceeding 350 PPM. East Anglia sits atop a massive Cretaceous chalk aquifer with minimal annual rainfall, resulting in extreme mineral saturation.

No, United Utilities delivers naturally soft water across almost all of North West England, averaging just 45 PPM (3.2° Clark). Sourced from the remote volcanic fells of the Lake District and Pennine moors, it causes minimal limescale.

Yorkshire Water features a striking geological divide: West and South Yorkshire (Leeds, Sheffield, Bradford) enjoy soft water (60–100 PPM) from gritstone Pennine moors, whereas East Yorkshire (Hull, Beverley) receives very hard chalk borehole water (300–340 PPM).

No, Scottish Water is famously and naturally soft across the entire country, averaging between 15 and 35 PPM (1 to 2.5° Clark). Scotland's ancient bedrock consists of impermeable granite and metamorphic schists with virtually no chalk or limestone.

No, Dŵr Cymru Welsh Water delivers naturally soft tap water across over 90% of Wales, averaging 45 PPM (3.2° Clark). Rainfall flowing across the ancient gritstones and sandstones of the Brecon Beacons and Snowdonia collects minimal dissolved minerals.

Approximately 85% of South West Water customers receive soft water (30–65 PPM) sourced from Dartmoor and Bodmin Moor granite catchments. Plymouth has some of the purest soft water in England (34 PPM), while East Devon (Honiton, Sidmouth) receives moderately hard groundwater (180–210 PPM).

Yes, Southern Water delivers hard to very hard tap water across Hampshire, Sussex, and Kent, averaging 280 PPM (19.6° Clark). The South Downs and North Downs chalk hills act as enormous calcium sponges, saturating groundwater before abstraction.

Yes, tap water supplied by Wessex Water across Bath, Somerset, Wiltshire, and Dorset is hard to very hard, averaging 290 PPM (20.3° Clark). Rich in calcium carbonate dissolved from famous Jurassic oolitic limestone (Bath Stone) and southern chalk hills.

Yes, Affinity Water delivers some of the hardest tap water in Great Britain, averaging 290 to 325 PPM (20.3° to 22.8° Clark). Over 65% of supply is drawn directly from deep chalk aquifers beneath Hertfordshire, Buckinghamshire, and Surrey.

Yes, South East Water delivers hard to very hard tap water, averaging 270 PPM (18.9° Clark). Three-quarters of supply is pumped from deep underground chalk and greensand aquifers across the North Downs and Weald.