Dunstable Water Hardness & Quality Report (2026)

Dunstable, the Central Bedfordshire town at the foot of the Chiltern Hills chalk scarp, is supplied by Affinity Water from the Chiltern Chalk Aquifer. Affinity Water holds licensed borehole abstractions in the Dunstable Downs chalk and the broader Chiltern Chalk Aquifer system — the Cretaceous Upper Chalk that forms the Chilterns escarpment rising dramatically above Dunstable at Ivinghoe Beacon and the Dunstable Downs. The chalk here is unconfined and highly permeable — recharge from the chalk downland plateau flows rapidly into the aquifer, dissolving very high calcium concentrations on a short residence path. The Dunstable Downs area is a primary recharge zone for the Chiltern chalk aquifer. Affinity Water treats chalk borehole supply at its Chilterns facilities and distributes to Dunstable and the south Bedfordshire area.

Dunstable's hard water — 236 mg/L (16.6°Clark) — reflects the Chilterns Chalk Aquifer directly beneath and behind the Dunstable Downs scarp. The Cretaceous Upper Chalk of the Chilterns at the scarp crest is among the most productive and calcium-concentrated chalk aquifer in England. The Drinking Water Inspectorate (DWI) classifies this supply as hard.

Limescale is a persistent household challenge in Dunstable. At 236 mg/L, limescale forms in kettles within two to three weeks and monthly or fortnightly descaling is advisable. Combi-boiler heat exchangers accumulate deposits steadily — annual boiler servicing and fitting an in-line scale inhibitor are strongly recommended. Showerheads, taps, and shower screens develop regular deposits. Washing-up liquid lathers poorly. Using Calgon monthly in the washing machine and maintaining a regular descaling routine is essential limescale management for Dunstable households on the Chiltern chalk supply.