Middlesbrough Water Hardness & Quality Report (2026)

Middlesbrough, the main town of the Teesside conurbation in the Tees Valley, is supplied by Northumbrian Water. Principal water sources include the River Tees catchment in County Durham and North Yorkshire, stored in Cow Green Reservoir in upper Teesdale and treated at Lartington Water Treatment Works near Barnard Castle. Supply is reinforced by the Kielder Transfer Scheme, which can transfer water from Kielder Water in Northumberland into the Tees system during periods of high demand or low rainfall. The River Tees drains the northern Pennines of County Durham and North Yorkshire, including the dramatic limestone gorge of High Force in Teesdale. Water is distributed from Northumbrian Water's treatment facilities to Middlesbrough and the wider Tees Valley industrial and residential area.

Middlesbrough's water hardness of 100 mg/L (7.0°Clark) reflects the varied Teesdale geology. The upper Tees drains through Carboniferous Great Limestone country in the North Pennines — the same limestone that underpins the dramatic waterfalls of Teesdale — which contributes a moderate calcium increment above the very soft yields of purely igneous or sandstone catchments. This is balanced by the Millstone Grit and sandstone moorland of the upper Pennine fells, which contribute softer water. The blended result sits near the soft–moderately soft boundary of the Drinking Water Inspectorate (DWI) classification.

Limescale is a moderate concern in Middlesbrough homes. At 100 mg/L, limescale builds up gradually — kettles typically need descaling every two months and deposits on showerheads and taps accumulate slowly. Combi-boiler heat exchangers are under modest limescale pressure, and annual boiler servicing with a limescale check is sensible. Washing-up liquid lathers reasonably well. Residents from harder-water southern cities will find limescale management notably less demanding in Middlesbrough. An annual Calgon dose in the washing machine and a regular kettle descale with white vinegar or a proprietary descaler is sufficient limescale care for most Teesside households.