The water drawn from a spring used for the actual whisky making is called “process water.” The water used in the condensers does not come into direct contact with the distillate and is called “cooling water”. It is normally drawn from a river nearby but can also be taken from the nearest municipality’s drinking-water source.
Water has an important influence on the whisky produced. It starts with the source and the condition of the soil. Water that streams over relatively soft soil, such as sand or limestone, absorbs more minerals than water flowing over hard, rocky terrain.
Each type of soil contains different minerals. For example, the granite soil found in parts of Scotland’s Speyside is very hard and doesn’t contain many minerals, resulting in water that is pure and soft.
In the Northern Highlands around Tain, though, the water is hard because it rises up to the surface through limestone, which is a sedimentary rock largely composed of calcium carbonate. On the Isle of Islay, the water flows over peaty soil which contains decayed seaweed and sphagnum (a type of moss) that release phenols. Phenols are the compounds responsible for the smoky taste of some whiskies. However, it is unlikely that phenols in water are noticeable in the final whisky.
The mineral content of water only influences the fermentation stage. When bottled, whisky is diluted with demineralised water, which doesn’t affect the flavour of the end product.
Our whisky Q&A is provided courtesy of SMWS ambassador Hans Offringa’s A Field Guide to Whisky: An expert compendium to take your passion and knowledge to the next level