The Boldons Water Hardness & Quality Report (2026)

Northumbrian Water supplies The Boldons — East Boldon and West Boldon — a pair of historic colliery villages between Sunderland and South Shields in South Tyneside, from Kielder Reservoir blended with local Permian Magnesian Limestone (Zechstein Dolomite) groundwater contributions in the South Tyneside coastal distribution zone, treated at Horsley Water Treatment Works near Washington. At 113.5 mg/L (8.0°Clark), The Boldons' water is slightly hard — harder than the Kielder-dominant central Sunderland zones (87 mg/L) — reflecting an elevated Magnesian Limestone groundwater contribution in the coastal east Durham–South Tyneside supply sub-zone.

The Boldons sit at the edge of the Permian Magnesian Limestone coastal belt where east Durham's limestone cliffs and plateau reach the South Tyneside borough. Northumbrian Water supplements the soft Kielder aqueduct supply in this coastal zone with a proportion of local Magnesian Limestone groundwater, elevating hardness to 113.5 mg/L with TDS 275.7 mg/L. This is consistent with other South Tyneside coastal communities receiving a moderate Magnesian Limestone blend — harder than the pure Kielder zones inland but softer than the most limestone-dominant east Durham coastal communities like Ryhope (210.5 mg/L).

At 113.5 mg/L, limescale is a moderate and manageable domestic concern in The Boldons. Descaling the kettle every six to eight weeks is typically adequate. The combi-boiler benefits from a standard scale inhibitor as a precaution. Washing-up liquid lathers adequately at everyday quantities. Taps and shower heads develop light deposits over several weeks; a monthly wipe with white vinegar keeps fixtures in good condition. The slightly hard supply reflects the Boldons' coastal position at the Kielder–Magnesian Limestone transition zone of the South Tyneside distribution network.