Sandown Water Hardness & Quality Report (2026)

Southern Water supplies Sandown on the south-east coast of the Isle of Wight from local catchments and groundwater reserves beneath the island. While northern Isle of Wight towns draw on softer Eocene clay catchments, Sandown sits directly on the chalk downland belt that runs east–west across the southern half of the island, and its supply is dominated by chalk aquifer groundwater accessed via boreholes into the Upper Cretaceous Chalk of the island's southern ridge, treated at island treatment works. At 287.5 mg/L (20.2°Clark), Sandown's water is very hard — markedly harder than Cowes on the northern coast — driven by the direct chalk geology beneath the town.

The Isle of Wight Chalk forms the prominent southern ridge running from Freshwater through the Downs to Culver Cliff east of Sandown. This chalk sequence is of Turonian and Cenomanian age and is highly porous and productive as an aquifer. Groundwater percolating through the chalk dissolves calcium carbonate extensively, emerging at boreholes with very high calcium bicarbonate concentrations — far higher than the island's northern catchments produce. Sandown's position at the foot of the chalk escarpment means its supply draws heavily on these mineralised chalk groundwaters.

Limescale is a significant daily challenge in Sandown. Kettles should be descaled fortnightly to prevent element damage and calcium particles in drinks. The combi-boiler requires a properly fitted scale inhibitor and annual professional servicing to protect the heat exchanger from calcium carbonate accumulation. Washing-up liquid produces noticeably less lather than in softer areas; considerably more product is needed per wash. Taps, shower screens, and basin mixers develop heavy limescale deposits quickly; a twice-weekly wipe with a proprietary descaler or white vinegar is advisable, and a whole-house water softener is strongly recommended for long-term protection.