Northumbrian Water Tap Water Quality

Northumbrian Water supplies North East England with drinking water drawn from Kielder Reservoir (Europe's largest man-made lake) and Derwent Reservoir, supplemented by Tees Valley catchments.

Northumbrian Water's crown jewel is Kielder Reservoir in Northumberland — at 200 billion litres, it is the largest man-made lake in Northern Europe. Upland Pennine and Cheviot catchments produce naturally soft, low-mineral water. Sunderland, Newcastle, and Gateshead typically see hardness of 50–75 mg/L. The Tees Valley and Teesside zones draw from slightly harder upland and lowland sources but remain well within the soft category. Iron is a monitored parameter in older urban distribution networks. Essex, which is supplied by Essex & Suffolk Water (a Northumbrian Water subsidiary), has very different — and much harder — water.

Typical water profile

With typical hardness of approximately 65 mg/L CaCO₃, water in the Northumbrian Water supply area is classified as soft. This means minimal limescale risk and good appliance longevity across the supply area.

Notable: Soft Pennine water for North East England. Low limescale risk. Good compliance record. Active PFAS improvement programme under DWI enforcement.

Is Northumbrian Water water safe to drink?

Yes. All treated water supplied by Northumbrian Water meets the UK Drinking Water Regulations. The Drinking Water Inspectorate (DWI) audits every water company annually — Northumbrian Water serves 2.7 million customers across 51 supply zones. Each zone is tested thousands of times per year and results are published in the annual compliance report.

However, water quality varies significantly between zones within the Northumbrian Water supply area. Your specific zone may have different hardness, nitrate, or THM levels from your neighbour in a different zone. That's why it's worth checking your exact postcode above.

How to check your Northumbrian Water zone

Enter your postcode in the box above to see zone-specific data for your address — including hardness, nitrates, lead, chlorine, fluoride, and THMs — drawn directly from Northumbrian Water's most recent annual compliance report.