Brighton Water Hardness & Quality Report (2026)

Brighton's water supply is managed by South East Water, which draws primarily from the South Downs Chalk Aquifer — one of the most significant chalk aquifer systems in southern England. Licensed boreholes sunk into the chalk beneath the South Downs National Park at sites including Falmer, Falmer Hill, Offham, and Hardham extract groundwater that has percolated through the chalk over decades. This is supplemented during peak demand by water transferred via the Southern Water and South East Water interconnection grid. Water is treated at Falmer Water Treatment Works and other facilities before distribution to Brighton and Hove and the surrounding coastal areas.

Brighton's very high hardness of 320 mg/L (22.5°Clark) is entirely a product of the South Downs Chalk. The South Downs are formed from Cretaceous Upper and Middle Chalk — a highly porous, calcium-rich limestone deposited approximately 70–100 million years ago. This chalk is the principal aquifer of South East England: rainwater infiltrating the chalk surface slowly dissolves calcium carbonate as it percolates downward over years, producing borehole water with very high calcium concentrations. Brighton sits on the coastal fringe of the chalk, where the aquifer has been used as a primary supply source since the 19th century.

Limescale is one of the most significant practical challenges for Brighton residents. At 320 mg/L, limescale forms extremely rapidly — a thick white crust appears in a kettle within one to two weeks of daily use, requiring weekly or fortnightly descaling. Combi-boilers are particularly vulnerable: limescale deposits inside the heat exchanger accumulate quickly at this hardness and can cause premature boiler failure without mitigation. Annual boiler servicing is essential, and fitting an in-line polyphosphate scale inhibitor or a full ion-exchange water softener is strongly recommended. Limescale on taps, showerheads, and shower screens requires aggressive regular descaling with a proprietary limescale remover. Washing-up liquid lathers very poorly at 320 mg/L.