Gosport Water Hardness & Quality Report (2026)

Gosport, the Hampshire town on the western shore of Portsmouth Harbour opposite Portsmouth, is supplied by Portsmouth Water — an independent water company drawing primarily from the South Downs Chalk Aquifer in south Hampshire. Portsmouth Water operates one of the most chalk-dependent supply systems in England, with licensed boreholes at Portsdown Hill and across the South Downs chalk escarpment of south Hampshire, including Havant Thicket and Farlington abstraction areas. This chalk aquifer — the Cretaceous Upper Chalk of the South Downs extending into Hampshire — provides the principal water resource for Portsmouth, Gosport, and the south Hampshire coastal strip. Water is treated at Portsmouth Water's Hampshire facilities before distribution across the Portsmouth–Gosport peninsula.

Gosport's very hard water — 254.5 mg/L (17.9°Clark) — reflects the South Downs Chalk Aquifer that Portsmouth Water exclusively relies upon. The chalk beneath south Hampshire is a thick sequence of Cretaceous Upper Chalk — the same geological formation as the white cliffs of the South Downs and the Isle of Wight chalk ridge opposite Gosport. Groundwater migrating through this chalk from the South Downs northward toward the coastal plain carries very high dissolved calcium concentrations, producing consistently hard water across all Portsmouth Water's supply area. The Drinking Water Inspectorate (DWI) classifies this supply as very hard.

Limescale is a significant household challenge in Gosport. At 254.5 mg/L, limescale forms rapidly in kettles — a white crust within one to two weeks requiring fortnightly descaling. Combi-boiler heat exchangers accumulate serious limescale deposits; annual boiler servicing with a limescale check is essential, and fitting an in-line polyphosphate scale inhibitor is strongly recommended. Showerheads, taps, and shower screens develop heavy deposits requiring regular limescale treatment. Washing-up liquid lathers poorly. Gosport homeowners should consider a full water softener for comprehensive protection against limescale damage across all plumbing and appliances.