UK region

Water hardness in London

Average 302 ppm across 330 postcode districts, classified as very hard.

  • Range 224 to 350 ppm
  • Counties 1
  • Suppliers Affinity Water, SES Water, South East Water, Thames Water
Regional average
302
ppm CaCO₃
Very Hard
Soft
Moderate
Hard
Very hard
0100200300400+
302
Avg ppm
224
Min ppm
350
Max ppm
330
Postcodes

London water hardness at a glance

  1. London water is very hard, averaging 302 ppm across 330 postcode districts.
  2. That is 95 ppm above the UK average of 207 ppm.
  3. Districts range from 224 ppm to 350 ppm.
  4. Suppliers: Affinity Water, SES Water, South East Water, Thames Water.
  5. Expect limescale on kettles, taps and showerheads; see the water softener guide.

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Water Hardness Across London

The average water hardness in the London region is 302 ppm, classified as very hard. Across 330 postcode districts, hardness ranges from 224 ppm to 350 ppm.

The region is served by Affinity Water, SES Water, South East Water, Thames Water. Water hardness varies by county; see the breakdown below or check your specific postcode.

London is covered by a single county, Greater London, though hardness still varies by postcode district. The region spans 13 towns and 330 postcode districts in total.

At 302 ppm, London ranks as very hard water nationally. Compare it against the 50 hardest water areas in the UK.

Worth reading: our water softener guide covers the best options for London residents, and our limescale removal guide has quick fixes for kettles and taps.

How hard is the water in your area if you live in London?

If London is your area, the water is very hard, averaging 302 ppm across the capital, but it varies noticeably by borough depending on which water company and treatment works supply your street. For detailed postcode-level data, see our dedicated London page with all 330 postcode districts.

Does London have hard water? Yes. Readings across the capital range from 224 to 350 ppm. Thames Water supplies most London postcodes; cross-check against Thames Water's own water hardness data.

London Water Hardness by Postcode
By county

Counties in London

Sorted by hardness: see how your county compares.

County Hardness PPM Level Postcodes
Greater London
302
302 ppm Very Hard 330
Suppliers

Water Companies in London

Tap on a company for full coverage area and hardness data.

Affinity Water

268 ppm Hard

SES Water

239 ppm Hard

South East Water

297 ppm Hard

Thames Water

302 ppm Very Hard

Hard Water Guides

Learn more about water hardness and how to manage it.

What Is Water Hardness? Hard Water Effects Solutions
Recommended

Products for London

Top picks for households in very hard water areas.

Splendid Twin Tank Water Softener

Twin-tank electric softener sized for 1 to 7 bedroom homes. Removes limescale from pipes, boilers, and appliances and delivers continuous soft water, with metered regeneration to keep salt use low.

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Philips Shower Filter

Instant improvement for skin and hair. Reduces chlorine and limescale at the showerhead, no plumbing needed. A good first step before committing to a full softener.

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FAQ

Common questions about London water

Is London's water hard or soft?
London is classified as very hard water, averaging 302 ppm across 330 postcode districts. Expect visible limescale on kettles and taps within weeks at this level.
Is tap water in London safe to drink?
Hardness is not a safety issue: the World Health Organization sets no health-based limit for water hardness, so hard and soft water are both fine to drink. Drinking water quality is regulated by the Drinking Water Inspectorate in England and Wales and the Drinking Water Quality Regulator in Scotland, and your water company publishes test results for your area.
Why is water in London very hard?
Water hardness in London depends on the geology: chalk and limestone aquifers dissolve calcium and magnesium into the supply, making it harder. Areas with sandstone or granite tend to be softer.
Does hard water affect boilers in London?
Over time, limescale acts as an insulator in heat exchangers, reducing efficiency by a few percentage points each year if untreated. A water softener can help protect your boiler.
What's the average water hardness in London?
The average water hardness across London is 302 ppm (parts per million), classified as very hard. It ranges from 224 ppm to 350 ppm across 330 postcode districts.
Does London have hard water?
Yes. London has hard water, averaging 302 ppm and ranging from 224 to 350 ppm across 330 postcode districts. Thames Water supplies most of the capital and publishes its own hardness figures, so you can cross-check your area against their data.
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