258mg of limescale minerals in every litre, the median across SW districts
Is South West London a hard water area?
Yes. Tap water across the SW postcode area is very hard, the top band on the scale water companies use, with a median of 258 mg/L calcium carbonate. It ranges from 247 mg/L in SW1A to 318 mg/L in SW4, from 27 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 SW district
Hardest first. Hard starts at 180 mg/L, very hard at 250.
| District | Area | mg/L | Hardness |
|---|---|---|---|
| SW4 | Lambeth | 318 | very hard |
| SW3 | Kensington and Chelsea | 313 | very hard |
| SW10 | Kensington and Chelsea | 281 | very hard |
| SW9 | Lambeth | 273 | very hard |
| SW16 | Lambeth | 268 | very hard |
| SW1H | Westminster | 268 | very hard |
| SW12 | Wandsworth | 263 | very hard |
| SW18 | Wandsworth | 262 | very hard |
| SW1V | Westminster | 262 | very hard |
| SW1Y | Westminster | 261 | very hard |
| SW13 | Richmond upon Thames | 260 | very hard |
| SW8 | Lambeth | 259 | very hard |
| SW11 | Wandsworth | 259 | very hard |
| SW17 | Wandsworth | 258 | very hard |
| SW1P | Westminster | 258 | very hard |
| SW2 | Lambeth | 257 | very hard |
| SW6 | Hammersmith and Fulham | 257 | very hard |
| SW20 | Merton | 256 | very hard |
| SW1X | Westminster | 256 | very hard |
| SW15 | Wandsworth | 255 | very hard |
| SW1W | Westminster | 255 | very hard |
| SW19 | Merton | 255 | very hard |
| SW1E | Westminster | 255 | very hard |
| SW7 | Kensington and Chelsea | 254 | very hard |
| SW5 | Kensington and Chelsea | 254 | very hard |
| SW14 | Richmond upon Thames | 247 | hard |
| SW1A | Westminster | 247 | hard |
What to do about it
Hard water: compare softener quotes
At 258 mg/L most SW 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 247 and 318 mg/L.
Softener quotes for South West London
At 258 mg/L most SW homes get their money back on a softener within a few years. Free quotes from installers covering your postcode.
Request a free assessment and we'll come back to you with local installer options for your area.
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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 South West London water
Is South West London a hard water area?
Yes. The median hardness across SW postcode districts is 258 mg/L calcium carbonate, which is very hard. 100% of the 27 districts we hold readings for are hard or very hard (180 mg/L and above).
What is the water hardness in South West London?
Between 247 and 318 mg/L depending on the district, with a median of 258. The hardest measured district is SW4 at 318 mg/L and the softest is SW1A at 247. Figures come from water company drinking-water tests.
Do I need a water softener in South West London?
In most SW homes a softener pays for itself: at 258 mg/L kettles, boilers and showers scale up quickly. Check your own district first, because hardness varies from 247 to 318 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.