Hook Water Hardness & Quality Report (2026)

Thames Water supplies Hook, a suburb of Kingston upon Thames in south-west London. Supply is drawn from the River Thames abstracted at Hampton and treated at Hampton Water Treatment Works, delivered via the Thames Water distribution network across the Kingston borough and south-west London. At 322 mg/L (22.6°Clark) and a TDS of 954.3 mg/L, Hook's water is very hard with extremely high dissolved mineral content — one of the hardest supplies in the Thames Water zone, reflecting the combined influence of chalk-dominated Thames catchment water and the North Downs Chalk aquifer contributions that elevate hardness in south-west London.

The River Thames arrives at Hampton having traversed the Chiltern Chalk, North Downs Chalk, and Cotswold limestone catchments. The North Downs immediately south of the Kingston area contribute high-hardness chalk groundwater to the Thames at multiple points, and the south-west London distribution zone draws on these combined chalk inputs. The result is that some supply zones in south-west London and Surrey consistently record hardness above 300 mg/L — comparable to the hardest chalk boreholes in the South East.

Limescale is an intense and relentless domestic challenge in Hook. Kettles must be descaled every one to two weeks to prevent rapid element degradation and calcium particles in drinks. Combi-boilers face a high risk of premature failure without a properly fitted, annually replaced scale inhibitor cartridge and regular professional servicing of the heat exchanger. Washing-up liquid requires substantially more product per wash to achieve adequate lather. Taps, shower screens, and basin mixers must be descaled weekly to prevent permanent hard-water staining, and a whole-house water softener is strongly recommended to protect all appliances, plumbing, and the boiler from severe limescale damage.