Holloway Water Hardness & Quality Report (2026)
Water Hardness
22°Clark31.3°fH17.5°dH
Source
mixed
pH Level
8.5
neutral = 7.0
Lead
0.005 mg/L
✓ Below action level
TDS
911.7 mg/L
Est. Daily Cost
£0.71
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 Holloway, your appliances are currently losing 42% efficiency due to mineral buildup.
| Appliance | In Holloway | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 1.5 yrs | 8.5 yrs | -82% |
| Washing Machine | 3 yrs | 12 yrs | -75% |
| Water Heater | 5 yrs | 15 yrs | -67% |
Regional Water Comparison
How Holloway compares to its nearest neighbours
| City | Hardness | Clark° | Risk | Source |
|---|---|---|---|---|
| ▶ Holloway, Greater London | 313 mg/L | 22° | 🔴 Very Hard | mixed |
| Barnsbury, Greater London | 214.5 mg/L | 15° | 🔴 Very Hard | mixed |
| Archway, Greater London | 283 mg/L | 19.9° | 🔴 Very Hard | mixed |
| Camden Town, Greater London | 295.5 mg/L | 20.7° | 🔴 Very Hard | mixed |
| King's Cross, Greater London | 214.5 mg/L | 15° | 🔴 Very Hard | mixed |
National Benchmark
How Holloway compares to the United Kingdom average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Holloway | 313 mg/L | 🔴 High |
| United Kingdom National Avg | 183 mg/L | 🔴 High |
| Livingston Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Holloway's Water Unique?
Local geology and source profile
Holloway, in the London Borough of Islington in inner north London, is supplied by Thames Water from the Lee Valley Reservoir chain — Walthamstow, King George, William Girling, and Chingford — and from the Lee Valley Chalk Aquifer via chalk boreholes in south Hertfordshire. The Lee Valley supply corridor that feeds north London is strongly influenced by chalk groundwater — the Cretaceous Chalk of the Hertfordshire dipslope drains into the Lee catchment, and the Lee valley reservoirs impound chalk-catchment Lee water with very high dissolved calcium. Thames Water's north London supply zone at Islington and Holloway draws disproportionately on the Lee valley chalk, producing exceptionally hard water. The TDS of 911.7 mg/L reflects the extraordinary mineral loading from chalk dissolution.
Holloway's extremely hard water — 313 mg/L (22.0°Clark) — is among the highest in Greater London and reflects the Lee Valley Chalk Aquifer's strong influence on Thames Water's inner north London supply. The chalk of the Hertfordshire Lee valley is among the most productive chalk aquifer sources in England. The Drinking Water Inspectorate (DWI) classifies this supply as very hard.
Limescale is an extreme daily challenge in Holloway. At 313 mg/L, very thick limescale forms in kettles within days and weekly descaling is essential. Combi-boiler heat exchangers face extreme limescale risk — annual boiler servicing with full limescale inspection and a polyphosphate scale inhibitor are non-negotiable. Showerheads, taps, and shower screens accumulate very heavy deposits rapidly. Washing-up liquid lathers virtually not at all. Holloway homeowners should very strongly consider a whole-house water softener for protection against the extreme north London Lee valley chalk supply.
Geology & Source: Supplied by Thames Water from Lee Valley Reservoirs and the Lee Valley Chalk Aquifer — Holloway's inner north London Islington position draws on Thames Water's chalk-dominated north London supply zone fed heavily from the Lee valley chalk aquifer of Hertfordshire, producing extremely hard water at 313 mg/L (22.0°Clark) — among the hardest supplies in Greater London.