How hard is my water? UK water hardness checker by postcode
We analysed more than 1.3 million customer orders and found some parts wear out up to twice as often depending on where you live. A few simple steps can help your appliances last longer.
Check your water hardness by postcode
We never store your postcode. Readings come from your water supplier's own published data.
The DWI hardness scale
Six bands, soft to very hard (mg/l CaCO₃).
- Soft
- 0–50
- Moderately soft
- 50–100
- Slightly hard
- 100–150
- Moderately hard
- 150–200
- Hard
- 200–300
- Very hard
- 300+
How hard and soft water affects your appliances
Living in extreme hard water areas, or extreme soft water areas, can drastically reduce the lifespan of your washing machine, but for different reasons:
We sell twice as many washing machine heating elements in very hard water areas as we do in soft water areas.
Based on 5,488 sold since 2023.
Shop heating elementsWe sell 38% more detergent dispensers in very hard water areas than we do in soft water areas.
Based on 6,810 sold since 2023.
Shop detergent dispensersWe sell 20% more washing machine filters in very hard water areas than we do in soft water areas.
Based on 14,966 sold since 2023.
Shop filtersWe sell 27% more door seals in soft water areas than we do in very hard water areas.
Based on 42,018 sold since 2023.
Shop door sealsRansom Spares sales data (GB, 2023–2026). Figures show correlation with water hardness, not a controlled measure of cause.
Hard or soft, a regular clean pays for itself
We recommend a monthly service wash if you live in a hard or soft water area, and a service wash every 6 months for all other areas.
What is hard water?
Hard water is water with a high quantity of dissolved mineral content, mainly calcium and magnesium. It's due to the type of ground that the water runs through before it reaches your tap. If the area you live in is surrounded by chalk and limestone hills then your water will likely contain more calcium and magnesium and measure hard. Hard water leaves behind limescale on anything it comes into contact with.
The 10 hardest and softest water areas in the UK
hardest → softestUse the postcode lookup above to check your water hardness.
| Area | Hardness band | Typical mg/l | Highest mg/l | Water company |
|---|---|---|---|---|
| Ipswich | Very hard | 354.7 | 517 | Anglian Water |
| Norwich | Very hard | 339.1 | 460.7 | Anglian Water |
| Watford | Very hard | 339 | 351 | Affinity Water |
| Dartford | Very hard | 331 | 355 | Thames Water |
| Harrow | Very hard | 331 | 363 | Affinity Water |
| Colchester | Very hard | 330.2 | 501.3 | Anglian Water |
| Stevenage | Very hard | 318 | 389 | Affinity Water |
| Cambridge | Very hard | 317.8 | 501.3 | South Staffs / Cambridge Water |
| Canterbury | Very hard | 308 | 350 | Southern Water |
| Luton | Very hard | 307 | 346 | Affinity Water |
| Harrogate | Soft | 27.7 | 47.5 | Yorkshire Water |
| Aberdeen | Soft | 26.7 | 98.1 | Scottish Water |
| Blackburn | Soft | 25.9 | 57.9 | United Utilities |
| Bolton | Soft | 23.9 | 45.9 | United Utilities |
| Huddersfield | Soft | 23.4 | 28.8 | Yorkshire Water |
| Lancaster | Soft | 22.9 | 89.8 | United Utilities |
| Inverness | Soft | 21.1 | 138.1 | Scottish Water |
| Glasgow | Soft | 18.4 | 58.9 | Scottish Water |
| Falkirk | Soft | 16.8 | 44.2 | Scottish Water |
| Halifax | Soft | 14.5 | 36.3 | Yorkshire Water |
Frequently asked questions
- How do I check my water hardness by postcode?
- Enter your postcode in the checker at the top of this page. We match it to your water supplier's published reading for your zone and show which of the six hardness bands you fall into, from soft to very hard.
- How is UK water hardness measured?
- Water hardness is measured in milligrams per litre of calcium. Basically, how much calcium and magnesium is dissolved in the water being tested. Water companies then categorise them based on the readings from soft to very hard.
- Does hard water damage washing machine heating elements?
- Yes. Over time limescale will gradually coat the heating element meaning it takes longer for the water to heat up i.e. less efficient. Because the heater element is having to work harder to heat the water it will fail sooner.
- Does soft water cause mould on washing machine door seals?
- Yes. You get more foamy suds in soft water which don't rinse away easily. The residue that is left behind becomes a breeding ground for mould. Mould will become visible in areas such as the door seal and detergent drawer.
- What is a washing machine service wash?
- It's a simple process that is designed to keep the inside of your washing machine clean and smelling fresh. A regular service wash stops limescale from building up and in soft water areas stops mould from taking hold which causes your washing machine to smell. The procedure is simple; empty a sachet of washing machine cleaner inside the drum and run the washing machine on a cycle at 55 degrees or higher.
- How accurate is the reading for my postcode?
- Water companies provide hardness readings by zone, not postcode, therefore all customers in the same zone will get the same reading.
- Which UK areas have the hardest water?
- South East, East Anglia, and London tend to have the hardest water, while many parts of Scotland, Wales, the North West and the South West tend to have softer water. Check your postcode above to see how hard your water is. Also, check out the table which compares the 10 hardest areas with the 10 softest areas.
How water hardness is measured: the DWI scale
We have taken all the water company readings for every zone in the UK and mapped the relevant postcode sectors to these zones. 8443 have the exact published reading and 2269 use the closest measured area. Each result is labelled with accuracy details.
The DWI six-band scale (mg/l CaCO₃)
- Soft
- 0–50 mg/l
- Moderately soft
- over 50 to 100 mg/l
- Slightly hard
- over 100 to 150 mg/l
- Moderately hard
- over 150 to 200 mg/l
- Hard
- over 200 to 300 mg/l
- Very hard
- over 300 mg/l