Biggin Hill Water Hardness & Quality Report (2026)

Affinity Water supplies Biggin Hill, the south-east London community in the London Borough of Bromley on the North Downs plateau — a community whose name is inseparable from the Battle of Britain: RAF Biggin Hill was the frontline fighter base from which Spitfire and Hurricane pilots of 11 Group flew throughout the summer of 1940, defending south-east England — from the North Downs Chalk (Cretaceous) aquifer boreholes in the south-east London Bromley supply zone, treated at Bough Beech Water Treatment Works near Edenbridge. At 263.5 mg/L (18.5°Clark), Biggin Hill'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 south-east London and north Kent chalk supply zone.

Biggin Hill sits directly on the North Downs Chalk plateau, at the highest point of the North Downs chalk escarpment above the Darent and Cray valleys. Affinity Water draws from deep North Downs Chalk boreholes in the Bromley–Biggin Hill supply zone, producing 263.5 mg/L with TDS 676 mg/L — very hard chalk water with an elevated TDS/hardness ratio (2.56) consistent with sulphate contributions from the Upper Greensand beneath the chalk, typical of the North Downs chalk borehole supply of the south-east London and Sevenoaks corridor.

At 263.5 mg/L, limescale is a persistent and significant household problem in Biggin Hill. 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. Biggin Hill's very hard North Downs chalk supply is as characteristic of this elevated plateau community as the sound of the air show overhead — the chalk that gives the North Downs its escarpment also mineralises the water in every household beneath the flight path.