Dorking Water Hardness & Quality Report (2026)

South East Water supplies Dorking, a market town in Surrey sitting in the Vale of Holmesdale at the foot of the North Downs chalk escarpment. Supply is drawn from a series of deep boreholes in the North Downs Chalk aquifer immediately behind the town, where the chalk dips steeply from the escarpment crest southward, treated at regional Surrey works before distribution. At 285.5 mg/L (20.0°Clark) and a TDS of 782.5 mg/L, Dorking's water is very hard — a direct consequence of the thick, pure Upper Cretaceous Chalk of the North Downs that rises immediately north of the town as a defining landscape feature.

The North Downs above Dorking comprise some of the thickest and most pure Upper Cretaceous Chalk in southern England — a highly porous aquifer recharging from rainfall over the downland crest. Groundwater percolating through the chalk from the escarpment dissolves calcium carbonate extensively during its underground transit to the borehole abstraction points at the foot of the escarpment near Dorking. The proximity of the chalk to the town means the groundwater has not travelled vast distances, but the sheer purity and thickness of the North Downs Chalk ensures very high calcium bicarbonate concentrations in the supply.

Limescale is a significant daily challenge in Dorking. Kettles require descaling fortnightly to prevent element damage and calcium particles in drinks. The combi-boiler needs a properly fitted scale inhibitor to guard against heat exchanger damage from the sustained North Downs chalk calcium load, and annual professional servicing is essential. Washing-up liquid produces reduced lather; considerably more product is needed per wash. Taps, shower heads, and basin mixers develop heavy limescale deposits within days to a week; a fortnightly descaling wipe with white vinegar or a proprietary product is advisable, and a whole-house water softener is strongly recommended.