Tap Water in PO40
Your water is pumped from underground sources in the chalk at Carisbrooke and th — Southern Water
Tap water in Your water is pumped from underground sources in the chalk at Carisbrooke and th, supplied by Southern Water, has the character of a chalk aquifer source, typical of southern and eastern England. It’s moderately soft, in the lower end of the national range, with a total hardness of 108 mg/L as CaCO₃. Bicarbonate is high at 284 mg/L: this water suits dark-roasted, milk-based coffee well, but will strip the acidity from lighter roasts and pour-over brewing.
Mineral composition
| mg/L | |||
|---|---|---|---|
| Calcium | ~99 | ||
| Magnesium | ~5 | ||
| Sodium | 14 | ||
| Sulfate | 16 | ||
| Chloride | 36 | ||
| Bicarbonate | ~284 | ||
| ~ Estimated from hardness and ion balance — not directly measured by the water company. | |||
Additional info
| Hardness | 108 as CaCO₃ |
| Alkalinity | 232.7 as CaCO₃ |
| pH | 7.29 |
| Conductivity | 544.80769 µS/cm |
| Source | Southern Water |
| Data year | 2024 |
What this means
Kettle & appliances
Some light mineral residue may appear in kettles over time, but significant limescale buildup is unlikely. No treatment needed for most appliances.
Espresso
A good range for espresso. Enough mineral content to provide body and balance acidity without posing a real scale risk to the machine. Most specialty coffee water targets fall in or near this band.
Filter & pour-over
Excellent for filter brewing. The slight mineral content adds body and sweetness without masking acidity, giving a balanced cup across most roast levels. This is close to the SCA’s recommended range for brewed coffee.
Drinking & cooking
Tastes clean with a slight mineral presence. Good all-round water for cooking; it won’t interfere with delicate flavours or leave noticeable deposits.
Bicarbonate
Heavily buffered water that resists pH change substantially: suited only to the darkest, most roast-forward beer styles (and even then may need dilution), while espresso at this level will taste dull, chalky, and lacking definition, with almost all origin character neutralised by the alkalinity.
Get the best from your water
PO40 tap water works well for espresso, brewing, baking, and aquarium use with little or no adjustment. It has too much mineral content for tea and horticulture; a bottled water blend is the better route for those.
Nearby areas
Data sourced from Southern Water (2024). Looking for a specific address? Look up your full postcode for the most accurate result.