The 20 hardest tap water areas
Hard water has a lot of dissolved calcium and magnesium. It is harmless to drink but leaves limescale on kettles, taps and pipes. Zones are ranked by average hardness in mg CaCO3/l. Where the company publishes no hardness table, the figure is the average for the zone shown by its own postcode checker and is marked as an estimate.
Only 582 zones have a hardness figure so far, so this is not a ranking of every area.
| # | Zone | Hardness |
|---|---|---|
| 1 | HartlepoolHartlepool, North East · Anglian Water | 490mg CaCO3/l · estimate |
| 2 | ThaxtedUttlesford, East of England · Affinity Water | 440mg CaCO3/l |
| 3 | Mid SuffolkMid Suffolk, East of England · Anglian Water | 404mg CaCO3/l · estimate |
| 4 | BraintreeBraintree, East of England · Anglian Water | 402mg CaCO3/l · estimate |
| 5 | WareEast Hertfordshire, East of England · Affinity Water | 388mg CaCO3/l |
| 6 | IpswichIpswich, East of England · Anglian Water | 384mg CaCO3/l · estimate |
| 7 | North NorfolkNorth Norfolk, East of England · Anglian Water | 376mg CaCO3/l · estimate |
| 8 | North LincolnshireNorth Lincolnshire, Yorkshire and The Humber · Anglian Water | 376mg CaCO3/l · estimate |
| 9 | Buntingford/TherfieldEast Hertfordshire, East of England · Affinity Water | 375mg CaCO3/l |
| 10 | Ashdon/Great SampfordUttlesford, East of England · Affinity Water | 373mg CaCO3/l |
| 11 | South KestevenSouth Kesteven, East Midlands · Anglian Water | 368mg CaCO3/l · estimate |
| 12 | HitchinNorth Hertfordshire, East of England · Affinity Water | 368mg CaCO3/l |
| 13 | West SuffolkWest Suffolk, East of England · Anglian Water | 365mg CaCO3/l · estimate |
| 14 | Potters Bar WestHertsmere, East of England · Affinity Water | 363mg CaCO3/l |
| 15 | Harrow SouthHarrow, London · Affinity Water | 363mg CaCO3/l |
| 16 | Great YarmouthGreat Yarmouth, East of England · Anglian Water | 361mg CaCO3/l · estimate |
| 17 | Harrow NorthHarrow, London · Affinity Water | 360mg CaCO3/l |
| 18 | Underground 1 ZoneTendring, East of England · Affinity Water | 360mg CaCO3/l |
| 19 | Saffron WaldenUttlesford, East of England · Affinity Water | 360mg CaCO3/l |
| 20 | South NorfolkSouth Norfolk, East of England · Anglian Water | 359mg CaCO3/l · estimate |
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Data collected from the water company for your area. Quality ranges are based on WHO guidelines and the UK drinking water regulations.