UK region

Water hardness in London

Average 286 ppm across 330 postcode districts — classified as hard.

Range 150–350 ppm
Counties 1
Suppliers Affinity Water, SES Water, Severn Trent Water, South East Water, Thames Water, Yorkshire Water

Regional average

286

ppm CaCO₃

Hard

Soft

Moderate

Hard

Very hard

0100200300400+

286

Avg ppm

150

Min ppm

350

Max ppm

330

Postcodes

Water Hardness Across London

The average water hardness in the London region is 286 ppm, classified as hard. Across 330 postcode districts, hardness ranges from 150 ppm to 350 ppm.

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

At 286 ppm, London ranks as hard water nationally. Compare it against the 50 hardest water areas in the UK.

Looking for London Water Hardness?

For detailed postcode-level data on London's water hardness (306 ppm avg, very hard), see our dedicated London page with all 330 postcode districts.

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	286	286 ppm	Hard	330

Suppliers

Water Companies in London

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

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 hard water areas.

Splendid Twin Tank Water Softener

From ~£400

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

From ~£30

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 hard water, averaging 286 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?

Yes. All tap water in London meets UK drinking water standards. Hardness affects taste and limescale buildup but not safety.

Why is water in London 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 286 ppm (parts per million), classified as hard. It ranges from 150 ppm to 350 ppm across 330 postcode districts.

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