Average 286 ppm across 330 postcodes and 13 towns.
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The average water hardness in Greater London is 286 ppm, classified as hard. Across 330 postcode districts in the London region, hardness ranges from 150 ppm to 350 ppm.
Greater London is served by Affinity Water and SES Water and Severn Trent Water and South East Water and Thames Water and Yorkshire Water. With hard water, residents may benefit from a water softener to reduce limescale and protect appliances.
Hardness varies across Greater London: Wembley has the hardest water at 332 ppm, while Watford is the softest at 233 ppm. The county spans 13 towns and 330 postcode districts in total.
At 286 ppm, Greater London ranks as hard water nationally. Compare it against the 50 hardest water areas in the UK.
Central London averages 306 ppm (very hard) — the highest in the Greater London area. See the full postcode breakdown and Thames Water supply data.
London Water Hardness by PostcodeSorted by hardness — tap a town for full details.
Companies supplying water to this county.
Every postcode district in the county, sorted by hardness.
Top picks for households in hard water areas.
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.
View on AmazonInstant 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.
View on AmazonLearn more about water hardness and how to manage it.