Great Bookham Water Hardness & Quality Report (2026)

Thames Water Utilities Limited supplies Great Bookham, a village in Mole Valley, Surrey. The water primarily comes from groundwater drawn through boreholes tapping the local Chalk aquifer. Treatment takes place at facilities like the Effingham or Leatherhead water treatment works. Here, the groundwater is filtered and disinfected, often with chlorine. Sometimes, it's mixed with surface water from the River Thames or reservoirs such as Queen Mother Reservoir to meet the community's needs. This utility serves a large portion of South East England, including Greater London.

The water originates in the North Downs, part of the Wealden anticline structure. Rainwater seeps into the permeable Upper and Middle Chalk formations, which are Cretaceous limestones. As the water flows through these rocks, it dissolves calcite from the chalk matrix, picking up minerals. This geological process, typical for chalk-fed groundwaters in the region, results in naturally high mineral content. Because there's little surface runoff, the water has low organic matter but is notably hard due to elevated calcium levels.

This very hard water causes significant limescale buildup in appliances like kettles, boilers, and washing machines, impacting their efficiency and lifespan. Hot water systems and fixtures often show chalky deposits. Homeowners can mitigate these issues through regular descaling with vinegar or citric acid, setting boiler temperatures to 60°C, and using scale collectors. Installing a water softener is frequently recommended to protect appliances, reduce soap consumption, and prevent scale, although it can slightly increase sodium intake. Thames Water monitors water quality, with typical pH levels between 7.2-7.6 for groundwater supplies, and keeps lead and copper within regulated limits.