Chester-le-Street Water Hardness & Quality Report (2026)

Chester-le-Street, the County Durham market town on the River Wear north of Durham city and south of Gateshead, is supplied by Northumbrian Water from the River Wear catchment and the Kielder Transfer Scheme. The Wear rises in the North Pennines above Weardale — draining the Carboniferous Limestone and Millstone Grit of the upper Pennines — and flows north through Durham and Chester-le-Street. Northumbrian Water abstracts from the upper Weardale and treats at Wear Valley treatment works, supplementing with Kielder Transfer soft water. Chester-le-Street sits downstream of Durham in the same Wear valley distribution zone, and the supply hardness of 140.5 mg/L is virtually identical to Durham city (139.5 mg/L), confirming both towns draw from the same Northumbrian Water Wear valley supply network.

Chester-le-Street's hardness of 140.5 mg/L (9.9°Clark) reflects the same North Pennine limestone and Kielder soft supply blend as Durham (139.5 mg/L) in the same River Wear valley Northumbrian Water distribution zone. The Drinking Water Inspectorate (DWI) classifies this supply as moderately soft.

Limescale is a moderate concern in Chester-le-Street. At 140.5 mg/L, limescale forms gradually in kettles and descaling every one to two months is typically sufficient. Combi-boiler heat exchangers accumulate modest deposits; annual servicing is sensible. Showerheads and taps develop light deposits. Washing-up liquid lathers reasonably well. A monthly Calgon tablet in the washing machine and a regular kettle descale is adequate limescale management for Chester-le-Street households on the Wear valley supply.