Water is a vital ingredient in a cup of coffee as it makes up around 98 per cent by volume of a cup of filter coffee. With the same coffee beans and the same method, hardness in water changes the taste of coffee enormously. Water act as a solvent, extracting the flavours in the coffee during the brewing process, whereas harder water produces a cup of coffee that lacks nuance, sweetness and complexity. 

We recommend filtering your tap water first or using bottled water with low mineral content if you can't get a good result from tap water.