Egham Water Hardness & Quality Report (2026)

Thames Water Utilities Limited provides Egham's water supply, drawing groundwater from boreholes that tap the Chalk aquifer within the London Basin. Key abstraction sites include the Staines or Chertsey boreholes. Water undergoes treatment at facilities like the Island Treatment Works, involving processes such as filtration, chlorination, and fluoridation. This supply serves millions of customers across London and the Thames Valley, including the Runnymede borough where Egham is situated. The watershed spans the Upper Thames Valley and London Basin, with recharge zones in the Chiltern Hills and North Downs.

The primary aquifer is the Cretaceous Chalk Group, a substantial formation of fractured limestone that serves as both a storage and transmission system for groundwater. This bedrock is inherently rich in calcium-bearing minerals, which naturally mineralizes the water, giving it a hard characteristic. While overlying Eocene clays and sands contribute minor ionic balance, the aquifer's significant depth and extended groundwater residence time allow for substantial mineral pickup, largely undiluted by surface runoff.

Homeowners in this hard water area will likely notice limescale buildup affecting appliances like kettles, boilers, showerheads, and washing machines, which can decrease their efficiency and shorten their lifespan. Dishwashers and coffee makers may experience clogged heating elements, and bathroom fixtures often develop white deposits. Routine descaling using solutions like vinegar or citric acid can help manage this buildup. For more robust protection of appliances and to improve soap lathering, installing a water softener is recommended, although this process may add sodium to the water. If you have concerns about sodium, rinsing drinking taps after softener use is an option. The water's pH typically ranges from 7.2–7.6, meeting UK standards.