Devizes Water Hardness & Quality Report (2026)

South West Water provides drinking water to Devizes, Wiltshire, drawing from a mix of sources across the South West peninsula. The supply primarily originates from upland reservoirs like Wistman's Wood and Roadford, fed by rainwater that percolates through thin, peaty soils atop impermeable bedrock in areas like Dartmoor and Exmoor. Surface water also comes from rivers such as the River Tamar and Bovey. Additionally, groundwater is extracted from boreholes tapping into Permian and Triassic sandstone aquifers beneath East Devon. Water treatment takes place at facilities including Crownhill and Chittering Cross, where processes like coagulation, filtration, chlorination, and fluoridation are employed to meet stringent Drinking Water Inspectorate standards.

The geology underlying the water sources significantly influences its mineral content. The moorland reservoirs collect soft water that has passed through granite and metamorphic bedrock dating back to the Carboniferous and Devonian periods, yielding low-mineral, peaty runoff. In contrast, groundwater from East Devon interacts with Permian and Triassic sandstone aquifers. These fossil-rich sedimentary layers, through prolonged rock-water contact, release more minerals, resulting in moderately mineralised water. When these softer surface waters are blended with the more mineralised groundwater, the resulting supply for Devizes typically exhibits a moderately hard character, with some limestone influences in parts of Wiltshire further contributing to this profile.

Homeowners in Devizes might notice some limescale buildup in appliances like kettles, showerheads, and boilers due to the moderately hard water, although it's generally less severe than in regions with very hard water. This scale can gradually reduce the efficiency of machines such as washing machines and dishwashers over time. To manage this, homeowners can regularly descale appliances using vinegar solutions, clean taps monthly, and maintain boiler temperatures below 60°C. Installing a water softener is an optional but potentially beneficial step for those who use a lot of hot water or already struggle with significant scale problems. The water's pH typically ranges from 7.5 to 8.5, and treatment processes, including orthophosphate addition, help manage potential issues like plumbosolvency, ensuring lead and copper levels remain well within safety limits.