Cwmbran Water Hardness & Quality Report (2026)

Cwmbran, the Torfaen new town in south-east Wales north of Newport, is supplied by Dŵr Cymru Welsh Water from Llandegfedd Reservoir — a large reservoir on a tributary of the River Usk in Monmouthshire east of Pontypool. Welsh Water draws from the River Usk and its tributary catchments in south-east Wales — the Usk rises in the Brecon Beacons and flows south-east through Devonian Old Red Sandstone country, through the Carboniferous Limestone belt at Abergavenny, and into the mixed geology of lowland Gwent (Monmouthshire). The Llandegfedd Reservoir catchment on the Usk fringe includes contributions from Carboniferous limestone country of the Abergavenny/Black Mountains fringe, adding a modest calcium increment above the very soft Brecon Beacons baseline. Welsh Water treats Llandegfedd supply and distributes to Cwmbran and the Torfaen valley.

Cwmbran's hardness of 130.5 mg/L (9.2°Clark) reflects the Llandegfedd supply blend — predominantly soft Devonian and Brecon Beacons upland water with a moderate Carboniferous Limestone contribution from the Abergavenny fringe catchment. The Drinking Water Inspectorate Wales classifies this supply as moderately soft.

Limescale is a moderate concern in Cwmbran. At 130.5 mg/L, limescale forms gradually and kettles need descaling every one to two months. 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 most Cwmbran households on the Usk valley supply.