Newquay Water Hardness & Quality Report (2026)

South West Water supplies Newquay on the north Cornish coast, drawing from a blend of surface water impoundments and groundwater sources across mid-Cornwall, treated at Trenance Water Treatment Works before distribution to the town. The unusually high hardness of 254.5 mg/L (17.9°Clark) for a Cornish coastal town reflects the influence of Devonian limestone and calcareous formations present in the geology of mid-Cornwall, which contribute dissolved calcium to groundwater sources blended into the wider South West Water supply network.

The geology beneath and around Newquay includes outcrops of Devonian metasedimentary rocks and volcanic sequences interspersed with thin limestones and calc-silicate beds. Although the predominant granite and slate of Cornwall are soft-water rock types, the Devonian limestone bands and thermally altered carbonate formations in this part of the county introduce calcium-rich groundwater into the supply blend. The high TDS of 761.8 mg/L confirms that significant dissolved mineral loading from these calcareous sources reaches the treatment and distribution network serving Newquay.

At 254.5 mg/L, limescale is a persistent domestic issue in Newquay, defying any expectation of soft Cornish water. Kettles should be descaled fortnightly to prevent element damage and calcium flakes in drinks. The combi-boiler requires a fitted scale inhibitor — essential at this hardness level — and annual professional servicing to check for heat exchanger deposits. Washing-up liquid requires noticeably more product per wash to achieve adequate lather in this very hard water. Taps, shower heads, and basin mixers develop heavy limescale deposits within days to a week; a weekly descaling wipe with white vinegar or a proprietary product is advisable, and a water softener is strongly recommended for comprehensive long-term protection.