How Windsor compares
At 302 mg/L (21.2 °Clark), Windsor is 24% above the median of the 411 English towns on this map (243 mg/L). It ranks 69 of 411 for hardness (1 is the hardest).
Water hardness in Windsor
Windsor has very hard water: limescale builds up quickly, so descale often and protect your boiler.
Data
| Value | 302 mg/L calcium carbonate 21.2 °Clark, 16.9 °dH |
|---|---|
| Band | very hard |
| Area | Berkshire |
| Population | 31,560 |
| Water company | Thames Water |
| Postcode checked | SL4 1NQ (SWA9) |
| Checked | 21 Oct 2026 |
| From the source | “Hardness (Total) as CaCO3 (mg/l) min 298 mean 302 max 305 | "mapCode":"SWA9"” |
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 Windsor?
The water company's figure for Windsor is 302 mg/L (21.2 °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
Slough 3 km Egham 7 km Staines 9 km Uxbridge 11 km Ashford 11 km Gerrards Cross 12 km Hayes 13 km Feltham 14 km