Llantwit Major Water Hardness & Quality Report (2026)
Water Hardness
~200–300 mg/L
Hardestimated · not lab-verified
Source
reservoir
pH Level
8.4
neutral = 7.0
Lead
0.001 mg/L
✓ Below action level
TDS
587.5 mg/L
Est. Daily Cost
£0.57
energy & soap waste
Source: DWI Data Portal · Updated 2026
0–99
mg/L
Soft
100–149
mg/L
Slightly Hard
150–199
mg/L
Moderately Hard
200–300
mg/L
Hard
300+
mg/L
Very Hard
Appliance Damage Report
In Llantwit Major, your appliances are currently losing 33% efficiency due to mineral buildup.
| Appliance | In Llantwit Major | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 5.7 yrs | 8.5 yrs | -33% |
| Washing Machine | 8 yrs | 12 yrs | -33% |
| Water Heater | 10 yrs | 15 yrs | -33% |
Regional Water Comparison
How Llantwit Major compares to its nearest neighbours
| City | Hardness | Clark° | Risk | Source |
|---|---|---|---|---|
| ▶ Llantwit Major, Wales | ≈ 200–300 mg/L | 17.5° | 🟠 Hard | reservoir |
| Coity, Wales | ≈ 150–200 mg/L | 5.4° | 🟡 Moderately Hard | reservoir |
| Bridgend, Wales | ≈ 0–100 mg/L | 4.3° | 🟢 Soft | reservoir |
| Aberkenfig, Wales | ≈ 0–100 mg/L | 5.5° | 🟢 Soft | reservoir |
| Llantrisant, Wales | ≈ 100–150 mg/L | 9.2° | 🟡 Slightly Hard | reservoir |
National Benchmark
How Llantwit Major compares to the United Kingdom average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Llantwit Major | ≈ 200–300 mg/L | 🟠 High |
| United Kingdom National Avg | 177 mg/L | 🟡 Moderate |
| Skipton Top Rated | 7.1 mg/L | 🟢 None |
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What Makes Llantwit Major's Water Unique?
Local geology and source profile
The water serving Llantwit Major comes to residents from Dŵr Cymru Welsh Water's Llwyn-On Reservoir and other upland reservoirs in south Wales. This water is then processed at regional treatment facilities located in the Vale of Glamorgan. The supply is characterized by a moderate hardness level, measuring around 9.2°Clark.
The water originates from south Wales' upland reservoir catchments. The underlying geological bedrock in this region is predominantly composed of Silurian mudstones and shales. These rock types contribute to the water's mineral content, resulting in a slightly hard classification for the supply. Unlike areas with limestone or chalk, these formations don't dissolve significant amounts of calcium and magnesium.
With a hardness of 9.2°Clark, you might notice some scale buildup over time, particularly in kettles and on shower heads. Using a water softener can help mitigate this, extending the life of your appliances and reducing the amount of soap or detergent needed for cleaning. It also means you'll likely use less cleaning product to achieve the same results, saving you money and effort around the house.
Geology & Source: South Wales upland reservoirs; geological bedrock is primarily Silurian mudstones and shales; produces slightly hard water
Other Wales Water Reports
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