Holyhead Water Hardness & Quality Report (2026)
Water Hardness
7.8°Clark11.2°fH6.2°dH
Source
reservoir
pH Level
7.8
neutral = 7.0
Lead
0.006 mg/L
✓ Below action level
TDS
264.7 mg/L
Est. Daily Cost
£0.25
energy & soap waste
Source: DWI Data Portal · Updated 2026
0–60
mg/L
Soft
61–120
mg/L
Moderately Hard
121–180
mg/L
Hard
180+
mg/L
Very Hard
Appliance Damage Report
In Holyhead, your appliances are currently losing 15% efficiency due to mineral buildup.
| Appliance | In Holyhead | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 5.9 yrs | 8.5 yrs | -31% |
| Washing Machine | 9.5 yrs | 12 yrs | -21% |
| Water Heater | 11.1 yrs | 15 yrs | -26% |
Regional Water Comparison
How Holyhead compares to its nearest neighbours
| City | Hardness | Clark° | Risk | Source |
|---|---|---|---|---|
| ▶ Holyhead, Wales | 111.5 mg/L | 7.8° | 🟡 Moderately Hard | reservoir |
| Bangor, Wales | 106.5 mg/L | 7.5° | 🟡 Moderately Hard | reservoir |
| Llandudno, Wales | 136.5 mg/L | 9.6° | 🟠 Hard | reservoir |
| Colwyn Bay, Wales | 73.5 mg/L | 5.2° | 🟡 Moderately Hard | reservoir |
| Aberystwyth, Wales | 68.5 mg/L | 4.8° | 🟡 Moderately Hard | reservoir |
National Benchmark
How Holyhead compares to the United Kingdom average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Holyhead | 111.5 mg/L | 🟡 Low |
| United Kingdom National Avg | 183 mg/L | 🔴 High |
| Livingston Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Holyhead's Water Unique?
Local geology and source profile
Welsh Water supplies Holyhead, the principal Irish Sea ferry port on Holy Island at the western tip of Anglesey — Wales's largest island and one of the UK's busiest ferry terminals, serving the daily routes to Dublin and Dún Laoghaire, and home to the ancient Caer Gybi Roman fort and the medieval St Cybi's Church within its walls — from Llyn Alaw, the largest freshwater lake in Anglesey, on the north Anglesey plateau, treated at Llyn Alaw Water Treatment Works. At 111.5 mg/L (7.8°Clark), Holyhead's water is slightly hard — reflecting calcium contributions from the Pre-Cambrian Mona Complex geology of Holy Island and north Anglesey, which contains bands of calc-silicate rocks, marble, and calcareous schist within the ancient Precambrian metamorphic complex.
Holyhead and Holy Island stand on the Holyhead Quartzite and the Mona Complex — a remarkable ancient Pre-Cambrian terrane of schist, phyllite, serpentinite, and calc-silicate marble bands. The Llyn Alaw reservoir catchment on north Anglesey overlies similar Pre-Cambrian and Carboniferous geology including the limestone fringe of Anglesey's Carboniferous south coast. The calc-silicate and marble bands of the Mona Complex contribute calcium to produce 111.5 mg/L with TDS 264.7 mg/L — slightly hard, harder than the mainland north Welsh Ordovician/Silurian soft supply from Abergele or Llandudno.
At 111.5 mg/L, limescale is a moderate and manageable domestic concern in Holyhead. 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 moderate deposits over several weeks; a monthly wipe with white vinegar keeps fixtures in good condition. Holyhead's slightly hard supply reflects the extraordinary ancient geology of Holy Island — Pre-Cambrian marble and calc-silicate rock, some of the oldest geological formations in the British Isles, mineralising the tap water of the Irish Sea's main Welsh ferry port.
Geology & Source: Supplied by Welsh Water from Llyn Alaw reservoir on the Anglesey Pre-Cambrian Mona Complex — treated at Llyn Alaw Water Treatment Works — produces slightly hard water at 111.5 mg/L (7.8°Clark).