Banbury Water Hardness & Quality Report (2026)

Banbury, the north Oxfordshire market town on the River Cherwell, is supplied by Severn Trent Water from the River Cherwell catchment and the Jurassic Limestone aquifer of north Oxfordshire. The River Cherwell rises on the Jurassic Inferior Oolite and Northampton Sand limestone escarpment near Charwelton in Northamptonshire and flows south through the Jurassic ironstone and limestone country of north Oxfordshire to Banbury and beyond. Severn Trent Water draws from the Cherwell and from licensed boreholes in the Jurassic Great Oolite and Inferior Oolite limestone formations of the north Oxfordshire plateau — productive limestone aquifers that dissolve high calcium concentrations. The Cherwell itself is a limestone-fed river contributing significant calcium from the north Oxfordshire Jurassic limestone country.

Banbury's hard water — 238 mg/L (16.7°Clark) — reflects the Jurassic Inferior Oolite and Great Oolite Limestone of the north Oxfordshire escarpment belt. The Jurassic oolitic limestone of the Cotswold/Edge Hill scarp in north Oxfordshire is a productive, calcium-rich aquifer — the same geological belt responsible for the hard Yeovil supply in Somerset at the other end of the Jurassic escarpment. The Drinking Water Inspectorate (DWI) classifies this supply as hard.

Limescale is a persistent household challenge in Banbury. At 238 mg/L, limescale forms in kettles within two to three weeks and monthly or fortnightly descaling is advisable. Combi-boiler heat exchangers accumulate deposits steadily — annual boiler servicing and fitting an in-line scale inhibitor are strongly recommended. Showerheads, taps, and shower screens develop regular deposits. Washing-up liquid lathers poorly. Using Calgon monthly in the washing machine and maintaining a regular descaling routine is essential limescale management for Banbury households on the Jurassic limestone supply.