Devizes Water Hardness & Quality Report (2026)

Wessex Water supplies Devizes, a historic market and canal town in central Wiltshire at the foot of the Marlborough Downs and the edge of Salisbury Plain. Supply is drawn from the Wiltshire Chalk aquifer beneath Salisbury Plain and the Marlborough Downs, treated at Calne and regional Wiltshire facilities before distribution across the Devizes supply zone. At 241.5 mg/L (16.9°Clark), Devizes's water is hard, driven by the thick, pure Upper Cretaceous Chalk of Salisbury Plain that underlies much of central Wiltshire and defines water chemistry across this part of the county.

The Marlborough Downs and Salisbury Plain chalk plateau immediately north and east of Devizes form one of England's largest expanses of uninterrupted chalk aquifer. Groundwater recharging from rainfall over these open downlands percolates through hundreds of metres of porous chalk, accumulating high calcium bicarbonate content during extended underground residence. The Wiltshire Chalk aquifer is a major source for Wessex Water across the county, and its consistent dissolution chemistry produces the hard water — at 241.5 mg/L with TDS 676.8 mg/L — characteristic of chalk-supplied communities throughout the Wiltshire plain.

At 241.5 mg/L, limescale is a persistent household challenge in Devizes. Kettles should be descaled monthly to prevent element degradation and chalky deposits in drinks. The combi-boiler benefits from a fitted scale inhibitor to protect the heat exchanger, and annual servicing is recommended. Washing-up liquid requires more product than in softer areas to achieve satisfactory lather. Taps and shower heads develop visible white limescale within one to two weeks; a fortnightly wipe with white vinegar or a proprietary descaler keeps fittings clean. The hard chalk water is an inescapable feature of life in Devizes — as much a part of the landscape as the famous Caen Hill flight of locks.