Milford Haven Water Hardness & Quality Report (2026)

Dŵr Cymru Welsh Water supplies Milford Haven (Aberdaugleddau), the deep-water port town on the Milford Haven Waterway in south-west Pembrokeshire — Europe's second busiest port by tonnage, the principal hub for UK liquefied natural gas imports, and set on one of the world's finest natural harbours — from Llys-y-frân Reservoir in the Preseli Hills north of Haverfordwest, treated at Llys-y-frân Water Treatment Works. At 47 mg/L (3.3°Clark), Milford Haven's water is very soft, consistent with the acid upland Ordovician and Silurian geology of the Preseli Hills that produces naturally pure, mineral-poor catchment water.

Llys-y-frân Reservoir is impounded on the Western Cleddau river in the heart of the Preseli Hills — a dramatic upland of Ordovician Volcanic (dolerite and rhyolite) and Cambrian Shale and Mudstone that forms the hilly hinterland of north Pembrokeshire. These ancient igneous and low-grade metamorphic rocks are impermeable and calcium-free, producing naturally very soft water with minimal mineral loading. The 47 mg/L with TDS 88.7 mg/L at Milford Haven is characteristic of the soft upland Preseli supply throughout west Pembrokeshire.

At 47 mg/L, Milford Haven's very soft water is comfortable for domestic use with minimal limescale demands. Descaling the kettle every three to four months is typically adequate. The combi-boiler benefits from a standard scale inhibitor as a standard precaution. Washing-up liquid lathers easily with modest quantities of product. Taps and shower heads remain largely scale-free with only occasional maintenance. In older properties, residents should briefly run the cold tap before drinking, as very soft water can be mildly corrosive to lead or copper plumbing — standard Welsh Water guidance for the very soft western Pembrokeshire supply communities.