Mold Water Hardness & Quality Report (2026)

Hafren Dyfrdwy (the Dee and Severn water company) supplies Mold (Yr Wyddgrug), the county town of Flintshire in north Wales — a handsome market town of Georgian architecture on the Alyn river below the Clwydian Range, home to a weekly indoor market (one of Wales's finest), a professional theatre (Theatr Clwyd), and a community at the centre of Flintshire's cultural and administrative life — from Llyn Brenig reservoir on the Clwydian Range above Denbigh, treated at Brenig Water Treatment Works. At 79.5 mg/L (5.6°Clark), Mold's water is soft — consistent with the impermeable Silurian and Ordovician greywacke, mudstone, and Carboniferous Limestone upland of the Clwydian Range that contributes minimal calcium to the reservoir catchment, dominated by impermeable moorland over ancient Palaeozoic rock.

Mold lies in the Alyn valley below the Clwydian Range where Hafren Dyfrdwy delivers Llyn Brenig reservoir supply — an upland reservoir on the Clwydian Silurian and Ordovician sedimentary upland with blanket moorland peat. The result is 79.5 mg/L with TDS 146 mg/L — soft water with a very low TDS/hardness ratio (1.84) characteristic of the Hafren Dyfrdwy Flintshire distribution zone at Buckley (79 mg/L) and Flint in the same north Wales upland reservoir supply corridor.

At 79.5 mg/L, limescale is a moderate and manageable domestic concern in Mold. Descaling the kettle every two to three months is typically adequate. The combi-boiler has low scaling risk. Washing-up liquid lathers readily with modest quantities. Taps and shower heads develop light deposits; a quarterly wipe with white vinegar keeps fixtures clean. Mold's soft supply is characteristic of the Clwydian Hills — the ancient Silurian and Ordovician upland that gives the range its heathery, peaty character also delivering clean, soft, low-mineralisation water to the households of Flintshire's county town.