Carterton Water Hardness & Quality Report (2026)

Thames Water supplies Carterton, a large residential town adjacent to RAF Brize Norton in west Oxfordshire, from Farmoor Reservoir on the Upper Thames and from the Cotswold Oolite (Great Oolite and Inferior Oolite) aquifer that underlies the west Oxfordshire limestone plateau, treated at Farmoor Water Treatment Works and distributed across the Witney and Carterton supply zone. At 228.5 mg/L (16.0°Clark), Carterton's water is hard — harder than Oxford city — reflecting the stronger influence of Jurassic Oolitic Limestone aquifer groundwater that dominates the west Oxfordshire supply zone west of the Thames.

The Cotswold limestone plateau around Carterton and Brize Norton is underlain by the Great Oolite and Inferior Oolite — Jurassic limestones of the Cotswold scarp and dip slope — which form a productive aquifer yielding hard, calcium-rich groundwater. This Jurassic limestone aquifer water contributes substantial calcium carbonate hardness to the Farmoor/west Oxfordshire supply blend, elevating hardness above the more dilute upper Thames surface water supply used for the Oxford area. The resulting 228.5 mg/L with TDS 623.3 mg/L reflects the dominant Cotswold limestone influence on the water chemistry in this part of the Thames Water upper Thames distribution zone.

At 228.5 mg/L, limescale is a persistent household challenge in Carterton. Kettles should be descaled monthly to maintain efficiency. The combi-boiler benefits from a fitted scale inhibitor and annual professional servicing. Washing-up liquid requires more product than in softer areas to achieve satisfactory lather. Taps and shower heads develop visible white limescale within one to two weeks; a fortnightly wipe with white vinegar or a proprietary descaling product keeps fittings clean and prevents hard-water staining from accumulating permanently on surfaces in this hard Cotswold limestone-supplied west Oxfordshire community.