What is Water?

Water is the key ingredient to life. Without it we would not exist. 60% of our body is made of water. It is what covers over 70% of the lands’ surface, with less than 1% available as potable drinking water. Water is precious, especially when it comes to our whiskey. Just like our bodies, your average bottle of whiskey is 60% water. So like alcohol, water is an ingredient, and an important one at that. 

Considerable time, money and effort is involved in securing a consistent supply. Distilleries in mountainous regions may often tap into local freshwater streams. Whereas more urban distilleries may source from slower flowing rivers, or access deep underground aquifers.

Acquiring a dedicated water source not only serves a distillery operationally, but can provide a unique selling point. Bottled water has long been marketed as an elixir of life. A naturally sourced, mineral rich, healthy alternative to stale, chlorinated, tap water. For many countries, tap water is free. Yet globally we consumed 600 billion bottles of the stuff in 2019. Place of provenance is a powerful tool in marketing food & beverage. But is there any truth behind it all? 

Really all you need to know about water comes from the Zoolander film


Firstly we need to lay down some basic facts. Water does taste different depending on the source. According to “Water Sommelier” Michael Mascha:

“Mineral content is the major contributor to water’s taste. There is also balance, the level of infused carbon dioxide; orientation, the water’s pH level; hardness, the amount of calcium and magnesium in the water; virginality, the water’s nitrogen content; and vintage, which can range from days to thousands of years.” 

These variables are caused by the land upon which the water has come from. The type of rocks to be more specific. As water runs out to sea, it slowly erodes the land upon which it flows. The bedrock affects the water’s mineral content or “Total Dissolved Solids” (TDS). TDS, alongside PH levels, dictates how salty, bitter and sour the water will taste, and bottled waters vary widely in these levels under laboratory testing.

TDS comprises dissolved salts (ions) and organic matter; magnesium, calcium, sodium, potassium, chloride nitrate and sulphate. Sodium is salty, calcium is sour, magnesium is bitter, with sulphate responsible for the metallic taste typically found in beer.


When we refer to beverage production the most important term is hardness. Water hardness is defined by their level of TDS. The more sediment, the ‘harder’ the water. Hard-water is likely to transfer firm or crisp textures to the whiskey, whereas soft-water offers a more neutral backdrop for the spirit to take hold. The majority of Scottish lands lie on igneous rock and therefore produce low-TDS soft-water for their single malt distillate to shine. Ireland, on the other hand, has a much varied water landscape. With soft water mostly up North, medium along the border, and hard in the majority of the Republic. Yet another factor showcasing the diversity of Irish Whiskey.


Bottled water must be filtered to become safe. There are a number of methods to achieve drinking quality, however some are more effective than others. To be bottled as “mineral water” in the EU, the water cannot undergo what is called reverse osmosis. This is an intense and effective filtration process where water is fed through an extremely fine membrane or filter under high pressure. This removes salts, heavy metals,organic compounds and chemicals. By making the water safe to drink we’ve ‘sterilised’ the minerality in the process. The minimal TDS level strips the water of its natural character, and essentially makes it “plain”, just like tap water.

Therefore, other methods of filtration exist:

  1. Sediment removal: A basic fibrous mesh is used to remove the largest sediments. Not fine enough to affect levels of TDS, but is ineffective against bacteria.
  2. Activated Carbon: This removes many bacteria, viruses and chemicals without affecting the TDS and subsequently the texture or taste.
  3. UV Light: Can remove up to 99.99% of bacteria and viruses by “deactivation”. However it does not filter any chemicals. Also maintains levels of TDS.

This is how bottled water is made safe to drink while retaining its ‘terroir’ or local character.

The implementation of all these methods is also how we create different styles of beer. The more calcium sulfate in your brewers’ wort for example, the drier and more bitter your IPA will turn out. For brewers who would like a clear canvass to experiment with different yeasts or hops, they will opt for the reverse osmosis method. The Pilsner style, originally brewed in the soft-water town of Pilsen, is created by breweries all around the world. In areas of hard-water, brewers will use distilled water to soften up the wort.

Save Water, Drink Whiskey

That is where the debate on the efficacy of water and its effects on whiskey flavour stems. Distillation. When water is distilled it’s stripped of its ions or salts, so the level of TDS is effectively zero. While this is true, when it comes to whiskey production, the addition of water occurs three times. Once before distillation, twice afterwards.The first occurence is when producing the wort. Similarly to brewing, hot water and grist (milled grain), are mixed together extracting the sugars from the barley. After filtering the sweet soup, yeast is added to the wort and fermentation begins. The particular PH and TDS of the water will affect the yeast, and therefore help mould the end flavour.

The second and third stages occur after distillation. Depending on the type of still used, our spirit comes out at a fiery 80%-97.2% pure alcohol. This is diluted down to 63%-70% ABV using more of that locally sourced water just before the liquid is casked. After years of maturation, the third and final stage is the bottling phase. Whereby as much as 20% of the bottle is filled with fresh water. 

So it boils down to the lengths a distillery will go to accentuate the character of the water into their final product. Much like Waterford Distillery has begun the investigation into terroir on whiskey, maybe there’s an avenue for investigating waters’ effect? Well one such distillery is doing just that.

The Glendree Distillery in County Clare are the only reported distillery in Europe to be fermenting, distilling and bottling entirely from rainwater collected from their own distillery rooftop.

Rainwater is considered “young” water, with extremely low minerality or TDS and is also nitrate free. Due to air pollution rainwater quality can depend on the region in which it is harvested, so we can vouch for Glendree and their fresh, Atlantic coastal air. Comparatively speaking, the Midleton Distillery receives its water from the Dungourney river, a clean flowing body that will have low minerality. The new Teeling Distillery in Newmarket Square, being in the heart of Dublin City opted to dig their own well, pumping in hard water rich in minerals.