Many people are unaware of how hard their home water supply is, despite it subtly affecting their daily lives. From cloudy drinking glasses and lack of soap suds to dry skin after washing, these are all signs of high calcium and magnesium levels and common indicators of hard water.
Although not typically a health risk, hard water can cause serious damage to your plumbing, central heating, and drainage systems. Scale build-up affects both hot and cold systems, including boilers, dishwashers, and washing machines, leading to corrosion, restricted flow, and even blockages.
If scale particles enter valves, they can cause leaks and damage mechanisms such as taps, flush systems, and pumps, resulting in costly repairs.
In hot water systems, scale builds up on heating elements and radiators, decreasing efficiency. These overworked systems are more likely to break down and consume more energy, thus driving up heating bills, which is especially difficult during today’s cost-of-living crisis. With new government plans to phase out gas boilers, maintaining your current system for as long as possible is financially wise. Addressing hard water early can prevent costly replacements and repairs, especially since insurance may not cover damage from poorly maintained pipes.
What Can You Do About Hard Water?
You can prevent these issues and maintain the efficiency and longevity of your plumbing systems by installing a water softener or conditioner. These systems are much more cost-effective than repeated boiler repairs or plumbing work.
Typically installed just after the mains supply (but before indoor taps), a softener lets you keep drinking unsoftened water while protecting the rest of your system.
The UK Areas with the Hardest Water
We’ve used online data to assess water hardness across UK counties and London Boroughs, categorizing them as soft, moderate, hard, or very hard.
| London Borough | Water Hardness figure (ppm) | Category |
| Barnet | 327 | Very hard |
| Enfield | 315.5 | Very hard |
| Harrow | 304.8 | Very hard |
| Barking and Dagenham | 301 | Very hard |
| Kingston upon Thames | 295.8 | Very hard |
| Westminster | 295.3 | Very hard |
| Brent | 292.5 | Very hard |
| Richmond upon Thames | 291.6 | Very hard |
| Havering | 290 | Very hard |
| Hounslow | 288 | Very hard |
| Hillingdon | 285.8 | Very hard |
| Greenwich | 284 | Very hard |
| Redbridge | 283 | Very hard |
| Ealing | 281 | Very hard |
| Newham | 278 | Very hard |
| Haringey | 276 | Very hard |
| Waltham Forest | 276 | Very hard |
| Lewisham | 275 | Very hard |
| Hammersmith and Fulham | 274 | Very hard |
| Kensington and Chelsea | 271 | Very hard |
| Wandsworth | 271 | Very hard |
| Croydon | 271 | Very hard |
| Islington | 266 | Very hard |
| Hackney | 266 | Very hard |
| Merton | 261 | Very hard |
| Bromley | 257.9 | Very hard |
| Sutton | 252.8 | Very hard |
| Tower Hamlets | 252 | Very hard |
| Southwark | 251 | Very hard |
| Camden | 245.7 | Hard |
| Lambeth | 236 | Hard |
| Bexley | 219.3 | Hard |
Key stats:
- 91% of the 32 boroughs have very hard water.
- The average hardness is 276 ppm (very hard).
- Barnet has the hardest water at 327 ppm.
- Bexley has the softest among them, though still hard, at 219.3 ppm.
The South East of the UK has predominantly chalk and limestone geology, which contributes to water hardness as it leads to high levels of calcium and magnesium in the water supply. The hardest water in London can be found in Barnet, with a score of 327, followed by Enfield, 315.5, and Harrow, 304.8.
The UK counties with the hardest water
| County | Water Hardness figure (ppm) | Category |
| Kent | 343 | Very hard |
| Cambridgeshire | 341 | Very hard |
| Gloucestershire | 341 | Very hard |
| Northamptonshire | 320 | Very hard |
| West Sussex | 319 | Very hard |
| Essex | 310 | Very hard |
| Bedfordshire | 300 | Very hard |
| Warwickshire | 300 | Very hard |
| Buckinghamshire | 286 | Very hard |
| Norfolk | 286 | Very hard |
| Hertfordshire | 280 | Very hard |
| Lincolnshire | 280 | Very hard |
| Nottinghamshire | 280 | Very hard |
| Oxfordshire | 280 | Very hard |
| Derbyshire | 278 | Very hard |
| Greater London | 274 | Very hard |
| Northumberland | 274 | Very hard |
| Tyne & Wear | 274 | Very hard |
| Dorset | 272 | Very hard |
| Shropshire | 270 | Very hard |
| East Sussex | 259 | Very hard |
| Rutland | 259 | Very hard |
| Somerset | 250 | Hard |
| Wiltshire | 250 | Hard |
| Hampshire | 249 | Hard |
| County Durham | 240 | Hard |
| Isle of Wight | 240 | Hard |
| South Gloucestershire | 228 | Hard |
| Suffolk | 220 | Hard |
| East Riding of Yorkshire | 219 | Hard |
| Leicestershire | 214 | Hard |
| Surrey | 214 | Hard |
| Worcestershire | 214 | Hard |
| South Yorkshire | 210 | Hard |
| North Somerset | 200 | Moderate |
| Staffordshire | 200 | Moderate |
| Bristol | 195 | Moderate |
| Devon | 185 | Moderate |
| Cornwall | 180 | Moderate |
| West Midlands | 180 | Moderate |
| Herefordshire | 179 | Moderate |
| Berkshire | 172 | Moderate |
| Merseyside | 170 | Moderate |
| Cheshire | 159 | Moderate |
| North Yorkshire | 157 | Moderate |
| Lancashire | 143 | Moderate |
| West Yorkshire | 129 | Moderate |
| Greater Manchester | 110 | Moderate |
| Cumbria | 28.69 | Soft |
Quick facts:
- 46% of counties have very hard water.
- Only Cumbria has soft water, due to its lack of chalk in bedrock and reliance on reservoirs.
- Northern areas like Manchester, Yorkshire, and Lancashire mostly have moderate water.
- Water hardness increases as you go further southeast, due to widespread chalk and limestone in regions like Kent, Essex, and Greater London.
Many northern regions such as West and North Yorkshire, Manchester, Cheshire, and Lancashire were identified as having moderately hard water. This is largely due to the area’s underlying geology. In contrast, areas like South Yorkshire and East Yorkshire showed higher levels of water hardness. Across Yorkshire as a whole, hardness levels vary due to differences in local rock formations.
Elsewhere in the UK, counties including Leicestershire, Surrey, Worcestershire, Suffolk, South Gloucestershire, County Durham, the Isle of Wight, Hampshire, Somerset, and Wiltshire were also found to have hard water.
Some of the hardest water in the UK is found in the South, particularly the South East, where chalk and limestone are abundant. Counties like Greater London, Dorset, Hertfordshire, and Essex all report very hard water. Kent, located in the far South East, had the highest recorded water hardness level—scoring 343—which makes it the hardest water area in the UK.
Summary
Although hard water isn’t dangerous to your health, it can wreak havoc on your plumbing and heating systems. It contributes to scale buildup, corrosion, and reduced system efficiency. The South East of England, with its chalk and limestone-rich terrain, has the UK’s highest water hardness levels. Kent leading the pack. The best way to combat the effects of hard water is by installing a water softener. When professionally fitted by a qualified plumber, it can help extend the life of your boiler, protect pipes and fixtures, and reduce your energy bills.