Poole Water Hardness & Quality Report (2026)

Poole, the large coastal town forming the western part of the Bournemouth–Christchurch–Poole conurbation in Dorset, is supplied by Bournemouth Water, part of the South West Water (Pennon Group) network. Poole's supply draws from a blend of sources including licensed boreholes into the Cretaceous Chalk Aquifer of the Isle of Purbeck — the chalk ridge that runs east–west through the Purbeck peninsula — and contributions from Eocene Boscombe Sand and Tertiary aquifer formations south of the New Forest. Water is treated and distributed by Bournemouth Water to the Poole harbour area. Poole's water is notably harder than neighbouring Bournemouth (90 mg/L), reflecting a greater chalk groundwater contribution in the eastern parts of the Bournemouth Water supply zone serving the Poole side of the conurbation.

Poole's hardness of 204 mg/L (14.3°Clark) reflects the Purbeck Chalk contribution. The Isle of Purbeck chalk ridge — the same formation that produces Lulworth Cove and Durdle Door's dramatic geology — is a Cretaceous Upper Chalk formation where groundwater percolating through the porous rock acquires high calcium carbonate concentrations. This chalk borehole component, blended with the softer Tertiary Eocene sand aquifer water used for the Bournemouth supply, raises Poole's hardness substantially above Bournemouth's. The blended supply is classified as moderately hard by the Drinking Water Inspectorate (DWI).

Limescale is a consistent household concern in Poole — noticeably harder than the equivalent supply across the harbour in Bournemouth. At 204 mg/L, limescale forms in kettles within three to four weeks and monthly descaling is advisable. Combi-boiler heat exchangers accumulate limescale deposits steadily — annual servicing with a limescale check is important, and fitting a scale inhibitor to the boiler cold feed is recommended. Showerheads and taps develop regular deposits. Washing-up liquid lathers moderately. Using Calgon monthly in the washing machine is adequate protection for most Poole households.