Is tap water in GU8 (Witley) hard or soft? Hard, 143 mg/L
Supplied by Thames Water
Tap water in Witley, supplied by Thames Water, has the character of a blended surface and groundwater supply, with no dominant mineral signature. It’s moderately soft, in the lower end of the national range, with a total hardness of 143 mg/L as CaCO₃.
Mineral composition
| mg/L | |
|---|---|
| Calcium | 53 |
| Magnesium | 3 |
| Sodium | 17 |
| Sulfate | 23 |
| Chloride | 41 |
| Bicarbonate | 123 |
Additional info
| Hardness | 143 as CaCO₃ |
| Alkalinity | 101 as CaCO₃ |
| pH | 7.4 |
| Conductivity | 322 µS/cm |
| Source | Thames 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
The buffering starts to become assertive: darker beer styles (porters, milds, brown ales) benefit from this level as it supports higher mash pH, but espresso will begin losing some of its brighter acidity, producing a rounder, heavier cup that flatters darker roasts while muting lighter ones.
Making coffee or tea? Tap water in GU8 is hard, at 143 mg/L. That’s more than coffee and tea need. Which bottled water to use instead · For tea
Get the best from your water
GU8 tap water works well for espresso, baking, and aquarium use with little or no adjustment. Brewing is within reach with salt additions. 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 Thames Water (2024). Looking for a specific address? Look up your full postcode for the most accurate result.