How Harpenden compares
At 332 mg/L (23.3 °Clark), Harpenden is 37% above the median of the 411 English towns on this map (243 mg/L). It ranks 27 of 411 for hardness (1 is the hardest).
Water hardness in Harpenden
Harpenden has very hard water: limescale builds up quickly, so descale often and protect your boiler.
Data
| Value | 332 mg/L calcium carbonate 23.3 °Clark, 18.6 °dH |
|---|---|
| Band | very hard |
| Area | Hertfordshire |
| Population | 30,674 |
| Water company | Affinity Water |
| Postcode checked | AL5 2SD |
| Checked | 21 Oct 2026 |
| From the source | “"Total Hardness":"332 mg/l","Calcium":"133 mg/l","Degrees English (Clarke)":"23.24","class":"very hard"” |
What it means for your home
Hard water drops a lot of scale when it is heated: in the kettle, the shower head and the element of an immersion heater or washing machine. Chalky rings on taps and spotty glasses are normal.
Set the dishwasher for hard water, dose detergent for your band and descale regularly. If you have a combi boiler, ask about a scale reducer at its next service. Hard water is safe to drink.
How often to descale
As a rule of thumb for very hard water, kettles and shower heads need descaling every three or four weeks. Descale whenever you see scale building up.
Common questions
Is hard water bad for you?
No. Hard water carries calcium and magnesium, minerals the body uses. Whether tap water is safe depends on germs and pollutants, which water companies test for, not on hardness.
Do I need a water softener in Harpenden?
The water company's figure for Harpenden is 332 mg/L (23.3 °Clark), which is very hard water. Usually not straight away. Set the dishwasher, dose detergent for your band and descale regularly. Get quotes for a softener only if scale is clearly damaging your boiler or appliances.
How do I find the value for my address?
Use your water company's postcode checker. Hardness can differ between districts, so check your own postcode, or test with strips or a drop test.
Nearby towns
St Albans 8 km Luton 8 km Hemel Hempstead 9 km Welwyn Garden City 10 km Hatfield 11 km Dunstable 14 km Stevenage 14 km North Watford 15 km