Swindon Water Hardness & Quality Report (2026)
Water Hardness
19.2°Clark27.4°fH15.3°dH
Source
mixed
pH Level
8.4
neutral = 7.0
Lead
0.007 mg/L
✓ Below action level
TDS
815.4 mg/L
Est. Daily Cost
£0.62
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 Swindon, your appliances are currently losing 36% efficiency due to mineral buildup.
| Appliance | In Swindon | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 1.5 yrs | 8.5 yrs | -82% |
| Washing Machine | 3.5 yrs | 12 yrs | -71% |
| Water Heater | 5 yrs | 15 yrs | -67% |
Regional Water Comparison
How Swindon compares to its nearest neighbours
| City | Hardness | Clark° | Risk | Source |
|---|---|---|---|---|
| ▶ Swindon, South West | 273.5 mg/L | 19.2° | 🔴 Very Hard | mixed |
| Southampton, South East | 268 mg/L | 18.8° | 🔴 Very Hard | groundwater |
| Reading, South East | 280 mg/L | 19.6° | 🔴 Very Hard | groundwater |
| Bristol, South West | 228.5 mg/L | 16° | 🔴 Very Hard | reservoir |
| Coventry, West Midlands | 55 mg/L | 3.9° | 🟢 Soft | reservoir |
National Benchmark
How Swindon compares to the United Kingdom average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Swindon | 273.5 mg/L | 🔴 High |
| United Kingdom National Avg | 164 mg/L | 🟠 Moderate |
| Glasgow Top Rated | 15 mg/L | 🟢 None |
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What Makes Swindon's Water Unique?
Local geology and source profile
Swindon's water supply is managed by Thames Water, drawing from the upper River Thames catchment in Wiltshire and Oxfordshire — the Thames rises near Cirencester in the Cotswolds and flows north-east past Swindon before turning east at Lechlade. Supply sources include direct river abstraction and licensed boreholes into the Great Oolite Limestone and Cornbrash aquifers of the upper Thames basin, augmented by transfers within Thames Water's southern and south-west grid. Water is treated at Farmoor Water Treatment Works near Oxford and at south-west Wiltshire facilities before distribution to Swindon and the surrounding North Wiltshire area — a city that has grown rapidly from a Victorian railway town into one of the UK's fastest-expanding urban centres.
Swindon's hardness of 273.5 mg/L (19.2°Clark) reflects the Jurassic limestone geology of the upper Thames catchment. The Cotswolds upland is formed from a thick sequence of Jurassic oolitic limestone and Great Oolite — cream-coloured, calcium-rich limestones that are moderately soluble in percolating water. The River Thames at this reach also passes over Corallian limestone and Oxfordian Clay-with-limestone outcrops. Borehole water from the Great Oolite aquifer carries calcium concentrations from direct dissolution of Jurassic carbonate rock, producing water classified as hard by the Drinking Water Inspectorate (DWI).
Limescale is a persistent challenge for Swindon households. At 273.5 mg/L, limescale forms quickly — a white crust appears in kettles within two to three weeks of daily use, and fortnightly or monthly descaling is advisable. Combi-boiler heat exchangers are at meaningful risk of limescale accumulation, and annual boiler servicing with inspection for deposits is strongly recommended. Fitting an in-line polyphosphate scale inhibitor to the boiler cold feed is a cost-effective investment in a hard-water area. Showerheads, taps, and bathroom tiles develop steady limescale deposits requiring regular attention. Washing-up liquid lathers poorly. Swindon homeowners, particularly those in newer housing developments on the town's expanding outer fringes, should factor limescale management into their property maintenance planning.
Geology & Source: Supplied by Thames Water from the River Thames headwaters in the Cotswolds and the Great Oolite Limestone aquifer — water passing through Jurassic limestone and the chalk-influenced upper Thames produces hard water at 273.5 mg/L (19.2°Clark).