How hard is my water?
Enter your postcode. We will tell you who supplies your water, the hardness band their supply typically falls in, what that means for your home, and link you to their own official checker for the exact figure.
The hardness bands
| Band | mg/l CaCO₃ | °Clark | °dH | What it means |
|---|---|---|---|---|
| Soft | 0–100 | 0–7 | 0–5.6 | No limescale problem. A softener would be wasted money. |
| Slightly hard | 100–150 | 7–10.5 | 5.6–8.4 | Barely noticeable. Filtration here is about taste. |
| Moderately hard | 150–200 | 10.5–14 | 8.4–11.2 | Slow scale on heated surfaces. An inhibitor is proportionate. |
| Hard | 200–300 | 14–21 | 11.2–16.9 | Scale is a recurring cost. Protect the boiler at least. |
| Very hard | 300+ | 21+ | 16.9+ | Among the hardest in the UK. A softener is worth costing out. |
Test your own tap instead
Your water company reports a supply zone. A test strip reports your kitchen.
A supply zone figure is usually right, but it is not the same as testing your tap — zones get re-blended, properties sit on boundaries, and some buildings have treatment already fitted that nobody mentioned. How to test water hardness at home.
Hardness test kits
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