How Slough compares
At 312 mg/L (21.9 °Clark), Slough is 28% above the median of the 411 English towns on this map (243 mg/L). It ranks 50 of 411 for hardness (1 is the hardest).
Water hardness in Slough
Slough has very hard water: limescale builds up quickly, so descale often and protect your boiler.
Data
| Value | 312 mg/L calcium carbonate 21.9 °Clark, 17.5 °dH |
|---|---|
| Band | very hard |
| Area | Berkshire |
| Population | 164,793 |
| Water company | Thames Water |
| Postcode checked | SL1 1DJ (SWA10) |
| Checked | 21 Oct 2026 |
| From the source | “Hardness (Total) as CaCO3 (mg/l) min 303 mean 312 max 325 | "mapCode":"SWA10"” |
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 Slough?
The water company's figure for Slough is 312 mg/L (21.9 °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
Windsor 3 km Gerrards Cross 9 km Uxbridge 9 km Egham 9 km Staines 11 km Chalfont Saint Peter 11 km Hayes 12 km Ashford 13 km