Tap Water in SW10
Chelsea — Thames Water
Tap water in Chelsea, supplied by Thames Water, has the character of a chalk aquifer source, typical of southern and eastern England. It's moderately hard, in the upper half of the national range, with a total hardness of 256 mg/L as CaCO₃.
Mineral composition
| mg/L | |
|---|---|
| Calcium | 96 |
| Magnesium | 4 |
| Sodium | 24 |
| Sulfate | 42 |
| Chloride | 34 |
| Bicarbonate | 250 |
Additional info
| Hardness | 256 as CaCO₃ |
| Alkalinity | 205 as CaCO₃ |
| pH | 7.8 |
| Conductivity | 538 µS/cm |
| Source | Thames Water |
| Data year | 2024 |
What this means
Kettle & appliances
Limescale buildup is noticeable and ongoing. Kettles will develop visible deposits within weeks, and heating elements in boilers and washing machines will need periodic attention. A water softener or scale inhibitor is worth considering.
Espresso
This water will scale espresso machines meaningfully. Flavour-wise, the high mineral content tends to flatten acidity and produce a heavier, less nuanced shot with lighter roasts. Darker roasts and milk-based drinks fare better: the body and density that hard water produces can carry well through milk. Regular descaling is essential, and filtration or blending with softer water is worth considering.
Filter & pour-over
The effect is more noticeable here than in espresso, because the higher water-to-coffee ratio amplifies the mineral influence. Lighter roasts will taste muted and uniform; origin character gets buried. Darker roasts hold up better, but the cup will lack the clarity that filter brewing is best at producing.
Drinking & cooking
The mineral taste is perceptible. Some people prefer it; others find it chalky. Hard water can affect how well soap and detergent lather, and it leaves visible residue on glass and stainless steel.
Bicarbonate
Extremely high buffering that makes this water difficult to work with for any brewing or coffee application without significant dilution or acid treatment: mash pH will sit stubbornly high, extraction will be unbalanced, and espresso will taste flat and chalky with no discernible acidity.
Closest water profiles
Nearby areas
Data sourced from Thames Water (2024). Looking for a specific address? Look up your full postcode for the most accurate result.