Portland Water Hardness & Quality Report (2026)

Wessex Water supplies Portland, the dramatic limestone promontory and town at the southern tip of the Chesil Beach in Dorset — the source of the Portland Stone that built St Paul's Cathedral and countless public buildings, and home of the former Portland Naval Base and HM Prison The Verne — from Dorset Chalk aquifer sources and the celebrated Sutton Poyntz springs near Weymouth, treated at Sutton Poyntz Water Treatment Works. At 238 mg/L (16.7°Clark) and a TDS of 667.2 mg/L, Portland's water is hard — consistent with the calcareous character of the Dorset chalk and Jurassic Portland Stone geology that makes the peninsula and its surrounding area so geologically distinctive.

Portland is geologically dominated by Jurassic Portland Limestone (Portland Stone) — the pale oolitic limestone of global fame — and the adjacent Cretaceous Chalk of the Dorset Downs, both highly calcareous formations. Wessex Water supplies Portland from the mainland, drawing on Sutton Poyntz chalk springs at the foot of the South Dorset Downs and chalk borehole sources, delivering 238 mg/L with TDS 667.2 mg/L to the peninsula — hard water where the limestone and chalk of the surrounding geology is faithfully reflected in the mineral content of the tap.

At 238 mg/L, limescale is a consistent household challenge in Portland. Kettles should be descaled monthly. The combi-boiler benefits from a fitted scale inhibitor and annual professional servicing. Washing-up liquid requires more product per wash. Taps and shower heads develop visible white limescale deposits within one to two weeks; a fortnightly wipe with white vinegar or a proprietary descaling product keeps fittings clean. The hard supply at Portland is an ironic geological coincidence — the island quarried to build the hardest and most durable public buildings in England also receives some of the hardest tap water in Dorset.