Horsham Water Hardness & Quality Report (2026)

South East Water provides the water supply for Horsham, West Sussex, serving around 2.2 million people across Kent, Sussex, and parts of Surrey. The primary source for Horsham's residents is groundwater drawn from the local Chalk aquifer. Key abstraction points include boreholes at Dudden Hill and Coolham works, with treatment taking place at facilities like the Billingshurst Water Treatment Works. This groundwater, originating from beneath the Weald anticline, is processed through filtration, chlorination, and fluoridation before entering the distribution network.

The geology influencing Horsham's water is dominated by the Chalk Group aquifer, a porous limestone formation of Late Cretaceous age. This bedrock, interbedded with flint, allows rainwater to percolate deeply, dissolving significant amounts of calcium carbonate and other minerals. While Tertiary sands and clays from the Lambeth Group are present, the highly soluble chalk is the main contributor to the water's chemistry. The Gault Clay above this formation acts as a confining layer, promoting the recharge of mineral-rich water, which ultimately results in a hard water supply.

Homeowners in Horsham may notice limescale buildup in appliances like kettles and boilers, which can reduce their efficiency and lifespan. For instance, dishwashers and washing machines can experience deposits that increase energy consumption. Regular descaling using household solutions like vinegar can help manage these issues. Many find that installing a water softener is an effective way to combat scaling and the soap scum that often appears on fixtures and glassware. The water's alkaline nature, with a typical pH around 7.5-8.0, is a characteristic of this chalk-derived supply, and South East Water ensures it meets stringent quality standards.