Calne Water Hardness & Quality Report (2026)

South West Water provides Calne and nearby communities in Wiltshire, South West England, with water primarily drawn from upland reservoirs like Roadford Reservoir, Wistman's, and Meldon. Additional supply comes from rivers such as the River Tamar and River Tavy. Water treatment takes place at facilities including Roadford Water Treatment Works and Crownhill Works. These sources tap into the high moorland watersheds of Dartmoor and Bodmin Moor, where rainfall rapidly flows off the landscape into storage. The water delivered to Calne is a blend typical of this region's supplies.

The underlying geology of Calne's water sources consists of Carboniferous and Devonian granite formations, interspersed with schists and slates. This impermeable granitic terrain, characteristic of Dartmoor and Bodmin Moor, limits the dissolution of minerals. Unlike areas with chalk or limestone bedrock, these uplands contribute very few soluble hardness ions, such as calcium and magnesium, to the water. Consequently, the water supply is naturally soft, with low overall mineralisation.

Homeowners in Calne will likely notice how easily soap lathers with this soft water, potentially reducing the amount of detergent needed. Appliances like kettles and washing machines generally experience less scale buildup, which can extend their lifespan and maintain energy efficiency. Given the naturally soft nature of the supply, a water softener isn't typically recommended. Instead, it's advisable to monitor for potential pipe corrosion due to the water's low buffering capacity. The Drinking Water Inspectorate standards are met, with treatment processes including coagulation, filtration, ozonation, and chloramination ensuring safe, clear water despite occasional moorland colour.