Tiverton Water Hardness & Quality Report (2026)

Tiverton, mid-Devon's principal market town on the River Exe at the head of the Exe valley — a prosperous wool and canal town — is supplied by South West Water from Wimbleball Reservoir on Exmoor and abstraction from the River Exe. Wimbleball Reservoir impounds the River Haddeo in the Brendon Hills above the Exe, draining the Devonian red sandstone and Carboniferous Culm Measures moorland of mid-Somerset and east Devon — rocks that produce moderately soft reservoir water. However, by the time this supply is distributed to Tiverton, it incorporates river water and local groundwater from the Permo-Triassic New Red Sandstone (Permian Breccia and Triassic Sandstone) that underlies the Exe valley floor between Tiverton and Exeter. The New Red Sandstone of the Exe vale carries calcium carbonate and calcium sulphate from the Triassic red-bed evaporite interbeds (same Keuper Marl formation as west Midlands and Lancashire), explaining the elevated 218 mg/L hardness and TDS of 607.5 mg/L (ratio 2.79). Water is treated at Tiverton Water Treatment Works before distribution.

The Permo-Triassic New Red Sandstone and Breccia of the Exe valley at Tiverton — the characteristic red rock of mid-Devon — is a continental desert sediment sequence deposited during the Permian and Triassic periods. These red beds contain calcium carbonate and calcium sulphate cements and interbedded evaporite horizons that dissolve into percolating groundwater, producing moderately hard, slightly sulphate-enriched water. This Triassic contribution lifts Tiverton's supply to 218 mg/L — noticeably harder than the soft Exmoor reservoir-only supply (60–80 mg/L) that would result from Wimbleball alone.

At 218 mg/L Tiverton's water is hard and limescale management is a regular household requirement. Kettles benefit from monthly descaling with citric acid. Shower screens develop a calcium film requiring regular white vinegar treatment. Washing-up liquid must be used generously. Combi-boilers and white goods benefit from inline scale inhibitor protection. Tiverton's handsome wool-town centre — the Grand Western Canal, the castle and the Pannier Market — sits at the heart of the red Devon landscape whose Permo-Triassic geology directly influences the hardness of every household tap.