Great Bookham Water Hardness & Quality Report (2026)

Affinity Water supplies Great Bookham, the Surrey village near Leatherhead in the Mole Valley — an attractive residential village beneath the Box Hill and Ranmore Common chalk escarpment, popular with North Downs walkers and National Trust visitors, adjacent to the Polesden Lacey Edwardian estate and the picturesque Norbury Park woodland — from the North Downs Chalk (Cretaceous) aquifer boreholes in the Surrey chalk supply zone, treated at West Hyde Water Treatment Works in west Hertfordshire. At 263 mg/L (18.4°Clark), Great Bookham's water is very hard — consistent with the deep productive Cretaceous Chalk aquifer of the North Downs that delivers persistently very hard, mineralised groundwater to the Affinity Water Surrey distribution zone.

Great Bookham lies on the North Downs chalk dip slope, directly beneath the Box Hill chalk escarpment. Affinity Water draws from deep North Downs Chalk boreholes in the Mole Valley supply zone, yielding 263 mg/L with TDS 691.4 mg/L — very hard chalk water with an elevated TDS/hardness ratio (2.63) consistent with sulphate contributions from the Upper Greensand (Gault Clay sequence) beneath the chalk, typical of deep Surrey North Downs chalk borehole supply.

At 263 mg/L, limescale is a persistent and significant household problem in Great Bookham. Kettles should be descaled every two to three weeks. The combi-boiler needs a fitted scale inhibitor and annual professional servicing. Washing-up liquid requires generous quantities for adequate lather. Taps and shower heads develop substantial white chalk deposits within a week to ten days; a fortnightly descaling with white vinegar or a proprietary product keeps fittings in good condition. Great Bookham's very hard North Downs chalk supply is as defining a characteristic of this Surrey village as the chalk escarpment of Box Hill that rises immediately above it — the chalk that creates the iconic landscape also mineralises every household tap.