Horley Water Hardness & Quality Report (2026)

South East Water provides drinking water to Horley in Surrey, South East England, serving a vast customer base across several counties. Their primary water source is groundwater, drawn from boreholes that tap into the significant Chalk aquifer situated beneath the Weald region. Key abstraction points are located near Gatwick and Crawley. Water undergoes rigorous treatment at facilities including the Horley Water Treatment Works, employing processes like aeration, filtration, chlorination, and fluoridation to ensure it meets all required drinking standards before reaching residents.

The geology underpinning Horley's water supply is dominated by the Chalk aquifer, a part of the Anglo-Paris Basin. This aquifer, formed from Upper Cretaceous limestone approximately 80 to 100 million years ago, is characterized by its high solubility. As rainwater percolates through the porous chalk and interbedded marl layers, it dissolves significant amounts of calcium and magnesium. This natural process imbues the groundwater with minerals, resulting in a characteristically hard water supply, unlike surface water sources which might be diluted by runoff. The Lower Greensand Group and Tunbridge Wells Sandstone formations also play a role in the local hydrogeology.

This naturally very hard water can lead to limescale accumulation in household appliances such as kettles, boilers, and showerheads, potentially decreasing their efficiency and shortening their operational lifespan. You might notice white deposits on bathroom fixtures or find that dishwashers and washing machines become clogged over time. While regular descaling with vinegar or the use of scale filters can offer some relief, installing a water softener is strongly recommended to prevent appliance failure and improve the lathering of soaps and detergents. The water quality, however, consistently meets Drinking Water Inspectorate standards, with monitored levels of lead, copper, and nitrates remaining within compliance limits.