225mg of limescale minerals in every litre, the median across KT districts
Is Kingston upon Thames a hard water area?
Yes. Tap water across the KT postcode area is hard, past the point where limescale starts costing money, with a median of 225 mg/L calcium carbonate. It ranges from 75 mg/L in KT10 to 287 mg/L in KT21, from 24 districts with their own water company reading.
- Soft
- 0 to 60 mg/L
- Moderately soft
- 60 to 120 mg/L
- Slightly hard
- 120 to 180 mg/L
- Hard
- 180 to 200 mg/L
- Very hard
- 200 to 400 mg/L
Hardness by KT district
Hardest first. Hard starts at 180 mg/L, very hard at 250.
| District | Area | mg/L | Hardness |
|---|---|---|---|
| KT21 | Mole Valley | 287 | very hard |
| KT13 | Elmbridge | 287 | very hard |
| KT1 | Kingston upon Thames | 281 | very hard |
| KT7 | Elmbridge | 268 | very hard |
| KT3 | Kingston upon Thames | 263 | very hard |
| KT9 | Kingston upon Thames | 262 | very hard |
| KT4 | Sutton | 260 | very hard |
| KT2 | Kingston upon Thames | 259 | very hard |
| KT8 | Elmbridge | 258 | very hard |
| KT6 | Kingston upon Thames | 255 | very hard |
| KT5 | Kingston upon Thames | 247 | hard |
| KT20 | Reigate and Banstead | 225 | hard |
| KT12 | Elmbridge | 225 | hard |
| KT23 | Mole Valley | 204 | hard |
| KT15 | Runnymede | 204 | hard |
| KT24 | Guildford | 154 | moderately hard |
| KT16 | Runnymede | 154 | moderately hard |
| KT22 | Mole Valley | 141 | moderately hard |
| KT14 | Woking | 141 | moderately hard |
| KT17 | Epsom and Ewell | 138 | moderately hard |
| KT19 | Epsom and Ewell | 88 | moderately soft |
| KT11 | Elmbridge | 88 | moderately soft |
| KT18 | Epsom and Ewell | 75 | moderately soft |
| KT10 | Elmbridge | 75 | moderately soft |
What to do about it
Hard water: compare softener quotes
At 225 mg/L most KT homes get their money back on a softener within a few years. A filter will not touch limescale; only a softener does.
- Free quotes
- Local installers
- No obligation
Check your own district first
The area figure is a median. Your district can sit anywhere between 75 and 287 mg/L.
Softener quotes for Kingston upon Thames
At 225 mg/L most KT homes get their money back on a softener within a few years. Free quotes from installers covering your postcode.
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Before you buy
- Do I need a water softener?The hardness bands, the symptoms, and when the answer is no
- Best water softener UKHarvey, Kinetico, BWT, Monarch and Water2Buy compared
- Water softener costUnit, fitting and salt, and how long the payback takes
- Installation explainedWhere it goes, the bypass tap, the drain, DIY or plumber
- Harvey vs KineticoThe two premium twin-cylinder brands, side by side
- Softener salt guideTablet, block or granular, and how much you get through
- Salt-free softenersConditioners and electronic descalers, honestly assessed
Questions about Kingston upon Thames water
Is Kingston upon Thames a hard water area?
Yes. The median hardness across KT postcode districts is 225 mg/L calcium carbonate, which is hard. 63% of the 24 districts we hold readings for are hard or very hard (180 mg/L and above).
What is the water hardness in Kingston upon Thames?
Between 75 and 287 mg/L depending on the district, with a median of 225. The hardest measured district is KT21 at 287 mg/L and the softest is KT10 at 75. Figures come from water company drinking-water tests.
Do I need a water softener in Kingston upon Thames?
In most KT homes a softener pays for itself: at 225 mg/L kettles, boilers and showers scale up quickly. Check your own district first, because hardness varies from 75 to 287 within the area.
Hardness as mg/L calcium carbonate from water company drinking-water tests and postcode checkers. See the UK hardness map for every area.