Dartford Water Hardness & Quality Report (2026)

Dartford, the north-west Kent town in the Darent valley at the North Downs chalk gap, is supplied by South East Water from the North Downs Chalk Aquifer in west Kent. South East Water holds licensed borehole abstractions in the chalk of the Darent valley chalk escarpment and the North Downs plateau south of Dartford — the Cretaceous Upper and Middle Chalk that forms the North Downs ridge between Dartford and Sevenoaks. The Darent is a classic Kent chalk stream rising from chalk springs on the North Downs scarp and flowing north through the chalk gap to the Thames estuary at Dartford. South East Water draws from chalk boreholes in the highly productive North Downs chalk, yielding very high dissolved calcium concentrations. The chalk at this Darent valley location is among the most productive in the Kent chalk system.

Dartford's extremely hard water — 318.5 mg/L (22.3°Clark) — reflects the North Downs Chalk Aquifer of west Kent at its most concentrated. The chalk supplies a TDS of 912.9 mg/L, reflecting very high total mineral content. The Cretaceous Chalk of the North Downs at Dartford is a thick, highly permeable chalk aquifer, and groundwater in the Darent valley chalk accumulates exceptional calcium concentrations. The Drinking Water Inspectorate (DWI) classifies this supply as very hard.

Limescale is an extremely serious daily challenge in Dartford. At 318.5 mg/L, very thick limescale forms in kettles within days requiring weekly descaling. Combi-boiler heat exchangers face extreme limescale risk — annual boiler servicing with a full limescale inspection and a polyphosphate scale inhibitor are essential. Showerheads, taps, and shower screens accumulate very heavy deposits extremely quickly. Washing-up liquid lathers very poorly. Dartford homeowners should strongly consider a whole-house water softener to protect boilers, appliances, and plumbing on this North Downs chalk supply.