Water is one of the most important raw materials in distilling, and it affects almost every aspect of the final spirit.
Choosing the right water can be the difference between creating a successful distillate and having to pour it down the drain. This is especially true when mashing, that process that converts grain into the sugar needed for fermentation.
Here, we address some of the basics of water analysis and how to choose the right water for fermentation.
Water Testing
Before mashing, test your water.
The first test that any water source should undergo is known as TOA—taste and odor acceptance—and it’s a very simple sensory test that almost anyone can conduct. To do it, simply collect a sample of the water in question and taste and smell it for any obvious faults. If the water has any perceivable flaws, then don’t use it for mashing.
Although that test might sound absurdly simple—and we have covered it before—it remains one of the most effective ways to determine whether a water source is suitable for mashing.
Once your water has passed a TOA test, it’s time to look at its actual chemical makeup. Because of its polar nature, water is extremely good at dissolving things such as salts, sugars, and other polar compounds. That means that most water sources available to distillers will not be pure, but rather a mixture of various ions and compounds along with water molecules.
The best way to find out exactly what’s in your water is to have a lab analyze it. Most public-water utilities already do that testing regularly, and the results are often accessible to the public on the organization’s website. For private water sources, you generally need to contact a lab and pay for testing. That process usually takes a couple of weeks and should be relatively inexpensive.
Indeed, many distillers who use public water sources also have their water tested at private labs, which often go into more detail compared to public-water reports.
The Parameters
Once you have the results of the water analysis, the next thing to do is to check the pH of the sample.
In general, the EPA recommends that the pH of potable water be between 6.5 and 8.5, though this is not a requirement and pHs can fall outside of that range. The actual pH pf the water sample will have little effect on your final mash pH—generally recommended to be from 5.2 to 5.6—as that’s determined by grain usage and other factors. Nonetheless, the pH of the water is a good gauge of the type of water you have and how it was processed.
For example, a higher pH of 8.3 often indicates that the water probably came from a hard water source and that you may need to filter it. On the other hand, a lower pH of 6.6 would indicate a slightly acidic water source that may need neutralization before use. More importantly, if the pH of the water is very high or very low—say 5.0 or 9.0—that’s a good indicator that something is wrong with the water and it should be investigated. For example, a pH of 4 on an otherwise perfect water profile is a sign that the report is probably not telling the full story and that more testing is required.
Once you’ve confirmed that the pH is correct, it’s time to look at the ions in the water.
Calcium is perhaps the most important ion in mashing, and it’s the primary ion responsible for things such as water hardness and mash pH. Calcium also plays an important role in stabilizing the enzymes present in the mash—especially alpha amylase, which is required to convert starch to sugar. Furthermore, calcium reacts with phosphates present in malt and grain to produce hydrogen ions, which lower the pH of the mash into the 5.2–5.6 range while also buffering it.
Traditionally, the recommended amount of calcium in water for mashing is between 50 and 150 ppm, though many distillers have found success with water that has far higher or lower concentrations. It’s important to understand, however, that calcium above 250 ppm may inhibit magnesium uptake by yeast and that below 50 ppm, the enzymes may struggle to convert starch.
The second ion that you as a distiller should know is magnesium. During the mash, magnesium acts similarly to calcium by reacting with phosphates to lower the pH. More importantly, magnesium is also an important nutrient for yeast health because it improves fermentation speed and ethanol tolerance. That trait is critical if you aim to achieve complete fermentations in a reasonable amount of time.
Generally, the suggested concentration of magnesium in mash water is not more than 40 ppm, though that’s not widely agreed-upon, and many people find success with higher levels. Also, because magnesium can also come from grain—and the amount varies widely based on fertilizer usage—it’s a good idea to get a professional lab to test a sample of your fermented mash. That will determine exactly how much magnesium was available to the yeast from the mashing process, letting you know whether you need to add more.
Finally, zinc is an important ion in mashing, as yeast use it in the cell-reproduction cycle, and it plays a critical role in the creation of alcohol dehydrogenase—the enzyme that allows yeast to produce alcohol. The amount of zinc needed for yeast to be healthy is minimal, with a maximum suggested concentration of as little as 0.05 ppm.
Fortunately, most city water sources have zinc levels around that concentration, though there are some that have a concentration of zero. In those cases, it’s wise to add a small amount of zinc to your mash water. That addition often comes in the form of a wide-spectrum yeast nutrient, which will also add various other micronutrients beneficial to the yeast.
Deal Breakers
Although almost any potable water can be used for mashing, there are a few ions and compounds that, as a distiller, you want to keep a special eye on. (Get it? Ion?)
The first of these deal-breaker components is chlorine. Chlorine and its sister compound, chloramine, are powerful oxidizers that water utilities often use to disinfect water before delivering it to the public. Unfortunately, their effects aren’t limited to bacteria, and elevated chlorine levels affect yeast health and subsequent flavor production.
The official disinfection limit for residual chlorine in public water is 4 ppm, but it’s often found at higher concentrations, especially during the hot summer months. Ideally, the level of residual chlorine in mash water is zero, and if you find elevated chlorine levels, you should consider carbon filtering or chemical neutralization to ensure that your water is suitable for use.
Note: Residual chlorine is not the same as chloride, which is the ion of chlorine. Higher chloride levels are safe to use—just try not to go above 200 ppm.
Another compound that you should watch out for is nitrate. Nitrate is a major part of fertilizer, and it’s common to find elevated levels in water that’s been exposed to agricultural runoff. Under fermentation conditions, nitrates can convert to nitrites, which impede yeast performance and produce off-flavors (though to a lesser degree than residual chlorine).
Nitrate is typically reported in terms of nitrogen, and the recommend maximum is 10 ppm. Unluckily—and unlike residual chlorine—you can’t effectively remove nitrates with carbon filtration; you’ll need either reverse osmosis or ion exchange. That would mean that you’ll need to expend considerably more effort to properly clean up your water.
A third compound that you should pay attention to is iron. The EPA doesn’t enforce a maximum iron content in water, but there are many state and local organizations that have limits. Iron is important to avoid in mashing—not because it affects the process, but because it can damage equipment. Iron dissolved in water can corrode stainless steel, especially in the presence of chlorides or sulfides. That can become a major problem for you as a distiller because these compounds are naturally present during the mashing process and because repeated exposure can prematurely wear out mash-vessel walls.
The federally recommended maximum concentration of iron in water is 0.3 ppm; you should strive to ensure that any water used in mashing is well below that limit. You can do that with filtration or ion exchange.
Finally, the last compound that you need to watch out for in mashing water is geosmin. Geosmin is an earthy- or musty-smelling compound produced by bacteria and algae, and it’s found in water sources around the world. The sensory threshold for geosmin is extremely low, with some people able to detect it at concentrations as low as 0.006 ppm. That makes it one of the most flavor-active compounds known.
What’s more, you can’t effectively remove geosmin via distillation or aging—which means that once a product has geosmin in it, there is practically no way to get it out. That makes geosmin a serious threat at all points in the spirits-making process.
Water reports don’t normally report geosmin. However, because of its low flavor threshold, detecting it is very easy—you only need to give your water a simple sniff (again, the TOA test). If you determine that a water source has geosmin, don’t use it. (Note: Some have reported reducing geosmin with reverse osmosis and carbon filtration, but those methods aren’t 100 percent effective and come with some risk.)
The Stuff of Life
Water plays an incredibly important role in the creation of virtually all distilled spirits. The flavor, texture, and palatability of spirits are all in part determined by the water used in each process.
Of course, this is only the beginning—the world of water chemistry and its effect on the mash is incredibly complex. Be sure to obtain your own water reports and to research each compound you find in detail. That’s the best way to ensure that you can quickly and accurately respond to problems, as they arise.