Corby Water Hardness & Quality Report (2026)

Corby, the north Northamptonshire new town and former steel-making centre, is supplied by Anglian Water from the Jurassic Lincolnshire Limestone (Lincolnshire Oolite) and Northampton Sand Formation aquifer resources. Corby sits on the Jurassic ironstone escarpment — the northward continuation of the Northamptonshire upland — where the Lincolnshire Oolite and Northampton Sand formations outcrop. These Jurassic aquifers were historically important for the iron ore that provided the raw material for Corby's steelworks, and the same limestone and sandstone formations also yield moderately hard groundwater with dissolved calcium from oolitic limestone cement. Anglian Water accesses these aquifers through licensed boreholes in the North Northamptonshire area and supplements with surface water resources.

Corby's hardness of 166 mg/L (11.6°Clark) reflects the Jurassic Lincolnshire Oolite and Northampton Sand aquifer contributions. The Lincolnshire Oolite is a Jurassic Bajocian oolitic limestone — a calcium carbonate rock whose aquifer yields moderately hard water. The Northampton Sand Formation, a Jurassic ferruginous sandstone, adds a further calcium and iron increment to the groundwater blend. These Jurassic formations produce harder water than the very soft Pennine uplands but considerably softer than the pure Cretaceous Chalk aquifer. The Drinking Water Inspectorate (DWI) classifies this supply as moderately hard.

Limescale is a regular household concern in Corby. At 166 mg/L, limescale forms in kettles within three to four weeks and monthly descaling is sensible. Combi-boiler heat exchangers accumulate deposits moderately — annual servicing with a limescale check and an in-line scale inhibitor are recommended. Showerheads and taps develop consistent deposits. Washing-up liquid lathers moderately. Using Calgon monthly in the washing machine and a regular descaling routine is appropriate limescale management for Corby households on the Jurassic limestone belt.