Ickenham Water Hardness & Quality Report (2026)

Affinity Water supplies Ickenham, a suburban village in the London Borough of Hillingdon in outer west London — an area of interwar semi-detached houses and the terminus of the Metropolitan and Piccadilly Underground lines at Ruislip Gardens — from Chiltern Chalk boreholes in the Colne Valley chalk belt west of London, treated at Iver Water Treatment Works near Iver in Buckinghamshire. At 292.5 mg/L (20.5°Clark) and a TDS of 835.4 mg/L, Ickenham's water is extremely hard — among the hardest in outer west London — consistent with the deeply confined Chiltern Chalk aquifer supply that characterises the Affinity Water Colne Valley and west London chalk distribution zone.

Ickenham sits at the south-eastern tip of the Chiltern Hills chalk plateau where the chalk dips beneath the Thames Valley gravels. Affinity Water supplies this area from chalk boreholes in the Colne Valley that tap the confined Upper Chalk at depth — a supply configuration that produces very high chalk mineral loading with TDS 835.4 mg/L at 292.5 mg/L hardness. The extremely hard supply is consistent with the Affinity Water west London chalk belt from Rickmansworth through Croxley Green (310.5 mg/L) to Denham and Iver.

At 292.5 mg/L, limescale is an extreme and persistent household challenge in Ickenham. Kettles must be descaled weekly to prevent rapid element failure. The combi-boiler faces very high risk of premature breakdown without a properly fitted, annually replaced scale inhibitor and regular professional servicing. Washing-up liquid barely lathers without very generous quantities of product. Taps, shower heads, and basin fittings develop heavy chalk encrustation within days; a weekly descaling with white vinegar or a proprietary product is essential. A whole-house water softener is very strongly recommended for all Ickenham households.