Sunninghill Water Hardness & Quality Report (2026)

Thames Water supplies Sunninghill, the east Berkshire village near Ascot in the Royal Borough of Windsor and Maidenhead — an exclusive community on the Windsor Forest heathland adjacent to Silwood Park (Imperial College), and close to the racecourse of Royal Ascot — from the River Thames at Walton in the east Berkshire and Windsor distribution zone, treated at Walton Water Treatment Works near Walton-on-Thames. At 178.5 mg/L (12.5°Clark), Sunninghill's water is hard — consistent with the chalk-tributary-influenced Thames at Walton, drawing moderate calcium loading from the North Downs, Chiltern, and Berkshire Downs chalk catchments above the Walton intake.

Sunninghill lies in the east Berkshire Windsor Forest heathland in the Thames Water Windsor distribution zone, supplied from the Thames at Walton. The chalk-tributary Thames above Walton carries moderate calcium from the Chalk of the North Downs, Chilterns, and Berkshire Downs, producing 178.5 mg/L with TDS 396.5 mg/L at Sunninghill — hard water with a relatively low TDS/hardness ratio (2.22) confirming predominantly chalk carbonate hardness, consistent with the Windsor–Slough–Ascot distribution zone.

At 178.5 mg/L, limescale is a consistent household concern in Sunninghill. Kettles benefit from descaling every three to four weeks. The combi-boiler should be fitted with a scale inhibitor and serviced annually. Washing-up liquid requires more product per wash. Taps and shower heads develop visible white limescale deposits within one to two weeks; a fortnightly wipe with white vinegar or a proprietary descaling product keeps fittings clean. The moderately hard Thames-supply water at Sunninghill is characteristic of the Windsor Forest fringe — less extreme than the chalk borehole-dominant zones of the Chilterns but a consistent domestic consideration in this east Berkshire heathland community.