Headstone Water Hardness & Quality Report (2026)

Affinity Water supplies Headstone in the London Borough of Harrow in north-west London, from the Colne Valley and deep Chiltern Chalk boreholes in Affinity Water's north-west London supply zone, treated at Chorleywood Water Treatment Works and distributed across Harrow and the north-west London chalk belt. At 265 mg/L (18.6°Clark) and a TDS of 712 mg/L, Headstone's water is very hard — driven by the chalk-dominated Colne Valley supply that is the defining characteristic of Affinity Water's service area across north-west London, Hertfordshire, and the Chiltern fringe.

Affinity Water draws from the Chiltern Chalk aquifer throughout its north-west London and Hertfordshire territory — a deep, productive aquifer recharged by the chalk plateau of the Chiltern Hills and delivering high-calcium, high-bicarbonate groundwater to the supply network. The Colne Valley follows the chalk dipslope south of the Chiltern scarp, and chalk borehole abstraction throughout the valley provides the primary supply for the Harrow and north-west London Affinity Water zone. The resulting 265 mg/L hardness with TDS 712 mg/L at Headstone is characteristic of the Harrow–Ruislip–Watford Affinity Water chalk supply corridor.

At 265 mg/L, limescale is a significant and persistent household challenge in Headstone. Kettles require descaling fortnightly to prevent element damage. The combi-boiler needs a properly fitted scale inhibitor and annual professional servicing to protect the heat exchanger. Washing-up liquid requires considerably more product per wash to achieve adequate lather. Taps, shower heads, and basin mixers develop heavy limescale deposits within one to two weeks; a fortnightly descaling wipe with white vinegar or a proprietary product is strongly advisable. A whole-house water softener is strongly recommended for Headstone households to protect appliances and plumbing from this very hard Chiltern Chalk supply.