UK Water Hardness by Area
Water hardness varies enormously across the UK — from the very hard, chalky water of London and the South East to the soft water of Scotland, Wales and the North West. Here's how the major postcode areas compare, and what kind of filter each one needs.
Want your exact area? Use our postcode water hardness checker for an instant result and a filter recommendation.
The big picture
The rule of thumb: south and east of a line from the Severn to the Humber, water is hard (chalk and limestone geology); north and west — the Pennines, Wales, Scotland and the South West peninsula — it's soft (granite and moorland catchments). The main exception is Birmingham, which is soft despite its Midlands location because it's supplied from the Elan Valley in Wales.
Water hardness by postcode area
Sorted hardest first. Figures are representative estimates from published water-company data.
| Area | Supplier | Hardness | Level |
|---|---|---|---|
| LU — Luton | Affinity Water | ~330 mg/L | Very hard |
| AL — St Albans | Affinity Water | ~320 mg/L | Very hard |
| PE — Peterborough | Anglian Water | ~320 mg/L | Very hard |
| WD — Watford | Affinity Water | ~315 mg/L | Very hard |
| HP — Hemel Hempstead | Affinity Water | ~310 mg/L | Very hard |
| SG — Stevenage | Affinity / Anglian | ~310 mg/L | Very hard |
| CB — Cambridge | Cambridge Water | ~310 mg/L | Very hard |
| HA — Harrow | Affinity Water | ~305 mg/L | Very hard |
| UB — Uxbridge | Affinity Water | ~305 mg/L | Very hard |
| SL — Slough | Affinity / Thames | ~305 mg/L | Very hard |
| MK — Milton Keynes | Anglian Water | ~305 mg/L | Very hard |
| NN — Northampton | Anglian Water | ~305 mg/L | Very hard |
| EN — Enfield | Thames / Affinity | ~300 mg/L | Very hard |
| CM — Chelmsford | Essex & Suffolk | ~300 mg/L | Very hard |
| N — North London | Thames Water | ~295 mg/L | Hard |
| NW — North-West London | Thames Water | ~295 mg/L | Hard |
| CR — Croydon | SES Water | ~295 mg/L | Hard |
| SM — Sutton | SES Water | ~295 mg/L | Hard |
| EC — Central London | Thames Water | ~290 mg/L | Hard |
| WC — Central London | Thames Water | ~290 mg/L | Hard |
| E — East London | Thames Water | ~290 mg/L | Hard |
| W — West London | Thames Water | ~290 mg/L | Hard |
| TW — Twickenham | Affinity / Thames | ~290 mg/L | Hard |
| SS — Southend | Essex & Suffolk | ~290 mg/L | Hard |
| SE — South-East London | Thames Water | ~285 mg/L | Hard |
| SW — South-West London | Thames Water | ~285 mg/L | Hard |
| KT — Kingston | SES / Affinity | ~285 mg/L | Hard |
| CO — Colchester | Essex & Suffolk / Anglian | ~285 mg/L | Hard |
| NR — Norwich | Anglian Water | ~285 mg/L | Hard |
| BR — Bromley | Thames Water | ~280 mg/L | Hard |
| DA — Dartford | Thames / SE Water | ~280 mg/L | Hard |
| CT — Canterbury | SE Water | ~280 mg/L | Hard |
| IP — Ipswich | Essex & Suffolk / Anglian | ~280 mg/L | Hard |
| IG — Ilford | Essex & Suffolk | ~270 mg/L | Hard |
| RM — Romford | Essex & Suffolk | ~270 mg/L | Hard |
| RG — Reading | Thames / SE Water | ~270 mg/L | Hard |
| ME — Medway | SE Water / Southern | ~270 mg/L | Hard |
| BN — Brighton | Southern / SE Water | ~270 mg/L | Hard |
| LN — Lincoln | Anglian Water | ~270 mg/L | Hard |
| WV — Wolverhampton | South Staffs Water | ~270 mg/L | Hard |
| WS — Walsall | South Staffs Water | ~270 mg/L | Hard |
| SP — Salisbury | Wessex Water | ~270 mg/L | Hard |
| SN — Swindon | Thames Water | ~270 mg/L | Hard |
| OX — Oxford | Thames Water | ~265 mg/L | Hard |
| DY — Dudley | South Staffs Water | ~265 mg/L | Hard |
| RH — Redhill | SES / Southern | ~260 mg/L | Hard |
| PO — Portsmouth | Portsmouth Water | ~260 mg/L | Hard |
| LE — Leicester | Severn Trent | ~260 mg/L | Hard |
| DT — Dorchester | Wessex Water | ~260 mg/L | Hard |
| TN — Tunbridge Wells | SE Water / Southern | ~255 mg/L | Hard |
| GU — Guildford | Various (SES/Thames) | ~250 mg/L | Hard |
| SO — Southampton | Southern Water | ~250 mg/L | Hard |
| CV — Coventry | Severn Trent | ~250 mg/L | Hard |
| NG — Nottingham | Severn Trent | ~250 mg/L | Hard |
| BS — Bristol | Bristol Water | ~250 mg/L | Hard |
| BA — Bath | Wessex / Bristol Water | ~250 mg/L | Hard |
| TA — Taunton | Wessex Water | ~230 mg/L | Hard |
| BH — Bournemouth | Bournemouth / South West | ~230 mg/L | Hard |
| HU — Hull (East Riding) | Yorkshire Water | ~230 mg/L | Hard |
| GL — Gloucester | Severn Trent | ~220 mg/L | Hard |
| DE — Derby | Severn Trent | ~200 mg/L | Hard |
| WR — Worcester | Severn Trent | ~180 mg/L | Moderately hard |
| YO — York | Yorkshire Water | ~180 mg/L | Moderately hard |
| ST — Stoke-on-Trent | Severn Trent | ~170 mg/L | Moderately hard |
| TF — Telford | Severn Trent | ~160 mg/L | Moderately hard |
| DN — Doncaster | Yorkshire Water | ~160 mg/L | Moderately hard |
| SY — Shrewsbury / Mid Wales | Severn Trent / Welsh | ~120 mg/L | Moderately hard |
| WF — Wakefield | Yorkshire Water | ~110 mg/L | Moderately hard |
| TS — Teesside | Northumbrian Water | ~100 mg/L | Moderately hard |
| LS — Leeds | Yorkshire Water | ~90 mg/L | Soft |
| S — Sheffield | Yorkshire Water | ~90 mg/L | Soft |
| SR — Sunderland | Northumbrian Water | ~90 mg/L | Soft |
| DL — Darlington | Northumbrian Water | ~90 mg/L | Soft |
| NP — Newport | Welsh Water | ~90 mg/L | Soft |
| BD — Bradford | Yorkshire Water | ~80 mg/L | Soft |
| CF — Cardiff | Welsh Water | ~75 mg/L | Soft |
| CW — Crewe | United Utilities | ~70 mg/L | Soft |
| CH — Chester | United Utilities / Welsh | ~70 mg/L | Soft |
| HD — Huddersfield | Yorkshire Water | ~70 mg/L | Soft |
| HX — Halifax | Yorkshire Water | ~70 mg/L | Soft |
| DH — Durham | Northumbrian Water | ~70 mg/L | Soft |
| TQ — Torquay | South West Water | ~60 mg/L | Soft |
| NE — Newcastle | Northumbrian Water | ~60 mg/L | Soft |
| SA — Swansea | Welsh Water | ~60 mg/L | Soft |
| LL — North Wales | Welsh Water | ~60 mg/L | Soft |
| B — Birmingham | Severn Trent (Elan Valley) | ~55 mg/L | Soft |
| EX — Exeter | South West Water | ~55 mg/L | Soft |
| WA — Warrington | United Utilities | ~55 mg/L | Soft |
| PL — Plymouth | South West Water | ~50 mg/L | Soft |
| LD — Llandrindod | Welsh Water | ~50 mg/L | Soft |
| TD — Scottish Borders | Scottish Water | ~50 mg/L | Soft |
| TR — Truro | South West Water | ~45 mg/L | Soft |
| PR — Preston | United Utilities | ~45 mg/L | Soft |
| SK — Stockport | United Utilities | ~45 mg/L | Soft |
| EH — Edinburgh | Scottish Water | ~45 mg/L | Soft |
| L — Liverpool | United Utilities | ~40 mg/L | Soft |
| BB — Blackburn | United Utilities | ~40 mg/L | Soft |
| WN — Wigan | United Utilities | ~40 mg/L | Soft |
| CA — Carlisle | United Utilities | ~40 mg/L | Soft |
| LA — Lancaster | United Utilities | ~40 mg/L | Soft |
| AB — Aberdeen | Scottish Water | ~40 mg/L | Soft |
| DD — Dundee | Scottish Water | ~40 mg/L | Soft |
| KY — Kirkcaldy | Scottish Water | ~40 mg/L | Soft |
| DG — Dumfries | Scottish Water | ~40 mg/L | Soft |
| M — Manchester | United Utilities | ~35 mg/L | Soft |
| BL — Bolton | United Utilities | ~35 mg/L | Soft |
| OL — Oldham | United Utilities | ~35 mg/L | Soft |
| ML — Motherwell | Scottish Water | ~35 mg/L | Soft |
| PH — Perth | Scottish Water | ~35 mg/L | Soft |
| FK — Falkirk | Scottish Water | ~35 mg/L | Soft |
| KA — Kilmarnock | Scottish Water | ~35 mg/L | Soft |
| G — Glasgow | Scottish Water | ~30 mg/L | Soft |
| IV — Inverness | Scottish Water | ~30 mg/L | Soft |
| PA — Paisley | Scottish Water | ~30 mg/L | Soft |
What hardness level means for your filter
- Very hard (300+ mg/L) — heavy limescale. A reverse osmosis system is well worth it.
- Hard (200–300 mg/L) — noticeable limescale. Reverse osmosis is our recommended choice; see best filters for hard water.
- Moderately hard (100–200 mg/L) — some scale. A filter helps; RO optional.
- Soft (under 100 mg/L) — little scale. A carbon filter for taste is usually plenty.
Hardness figures are area-level estimates based on the main supplier for each postcode area; supply zones don't map exactly to postcodes. Check your water company for your precise figure. Hardness is not a health risk — see is my tap water safe.