Calne Water Hardness & Quality Report (2026)

Wessex Water supplies Calne, a market town in north Wiltshire on the edge of the Marlborough Downs. Supply is drawn from the Wiltshire Chalk aquifer beneath the Marlborough Downs and from the Upper Thames catchment tributaries that drain the chalk and limestone country of north Wiltshire, treated at Calne Water Treatment Works and regional Wessex facilities. At 244 mg/L (17.1°Clark), Calne's water is hard — consistent with the chalk and Jurassic limestone geology that underlies north Wiltshire and provides the dominant groundwater character for the Calne supply zone.

The Marlborough Downs north of Calne are underlain by Upper Cretaceous Chalk of the Berkshire–Wiltshire chalk plateau, a productive aquifer recharging from rainfall over the open downland. Groundwater from the chalk percolates through the porous limestone over extended residence times, accumulating high calcium bicarbonate content before reaching abstraction boreholes. The Upper Thames tributaries draining the chalk and Jurassic Oolitic Limestone of north Wiltshire contribute comparable hardness from surface water sources, together with a TDS of 691.3 mg/L reflecting the substantial dissolved mineral load typical of this chalk and limestone landscape.

At 244 mg/L, limescale is a persistent household challenge in Calne. Kettles should be descaled monthly to prevent element degradation and calcium 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 descaling solution is recommended to prevent hard-water staining from building up permanently on fixtures and seals throughout the house.