Water is the most important ingredient in beer and most people get it wrong - because they overthink it. This is my detailed (or simple, your choice) guide to understanding the most important aspects of brewing water. It's really not as complicated as most people think. A proper water profile can take your beer to the next level and make good beers great! Too-long-didn't-read's at the start of each section. Read or skip the details, your choice.

There are essentially only two aspects of water chemistry that are important to talk about when it comes to beer: Residual alkalinity and pH and the mineral composition.

Alkalinity and residual alkalinity

TLDR

  • A high residual alkalinity means a high buffering capacity and resistance to changes in pH
  • Bicarbonate (HCO3-) is the primary compound in brewing water acting as a pH buffer, increasing alkalinity
  • Bicarbonate itself doesn't taste of anything, but is the compound that CO2 is dissolved as when drinks are carbonated
  • Cations like Ca2+ and Mg2+ neutralize and lower the buffering capacity of bicarbonate, decreasing alkalinity
  • Residual alkalinity takes into account the reduction in buffering capacity as a result of the presence of cations like Ca2+ and Mg2+, and to some extent also the grain bill
  • Alkalinity is irrelevant, only the residual alkalinity matters in practice
  • Pre-boiling your brewing water does not reduce the residual alkalinity much, only the concentration of cations

This is perhaps the most important, because it directly impacts the pH of the water and thus both the taste of the end result as well as the mash efficiency. Alkalinity is a term describing the buffering capacity of the water, or in other words its ability to neutralize acids (and bases) and a high alkalinity will reduce the impact of acids and the resulting change in pH. The main compound impacting the alkalinity in drinking water most places is bicarbonate (HCO3-). Most water sources have some level of bicarbonate because CO2 readily dissolves in water from the atmosphere and from other sources such as limestone in groundwater deposits, and will be dissolved in the form of bicarbonate. In fact, the same thing happens when beer is carbonated with CO2 to help release all the wonderful volatile aromatic compounds from the liquid, it's just a hell of a lot more bicarbonate (probably 2000-3000 ppm or more). Already now we don't have to talk about how it impacts taste by itself because everyone knows how sparkling water tastes. Bicarbonate itself doesn't taste of anything, so you shouldn't try to copy the exact bicarbonate levels from recipes from other brewers. It's simply a matter of dialing in the pH, as you'll learn about below.

If the water contains a high concentration of bicarbonate it has a high alkalinity. As bicarbonate also helps with stabilizing the pH during the mash it's good to have some level of it, say 50-100 ppm (mg/L), or else the pH can drop too low. Too much of it on the other hand will negatively affect the mash efficiency because of the increased pH outside the optimal range (5.2 - 5.6) of the amylase enzymes naturally present in the malt, which the brewer takes advantage of for the saccharification of starch present in the endosperm into smaller, fermentable sugars..

So, what's residual alkalinity then? Well, now we also need to talk a bit about "hard" water. Generally a high bicarbonate content also means a high affinity for cations, especially Ca2+ and Mg2+, and so the water is also likely to have a higher concentration of cations. Water with a high concentration of cations is what we would normally call "hard" water, and the two generally go hand in hand, especially in groundwater sources. By binding (electrostatically) with bicarbonate cations neutralize the buffering capacity of bicarbonate thus lowering the overall alkalinity of the water. The term taking this effect into account is called the residual alkalinity and is the only thing relevant to the brewer in practice. This effect is also the reason why some people with very hard water choose to boil their brewing water before brewing with it, because bicarbonate precipitates with both Ca2+ and Mg2+ forming limescale (CaCO3) and magnesium carbonate MgCO3, reducing the overall content of both. This hardly reduces the residual alkalinity, because, as mentioned, Ca2+ and Mg2+ both reduces the alkalinity, but they are also being removed by the boil. So if you choose to boil your brewing water, it should only be for the purpose of lowering the concentration of Ca2+ and Mg2+ ions (to be able to add salts without raising the cation levels into the extreme), and this results in reduced hardness of the water, not so much the alkalinity, because only the residual alkalinity counts in practice!

Mash pH

TLDR

  • A proper mash is all about manipulating enzymes and their activity by ensuring a proper temperature and pH, TOGETHER!
  • The optimal mash pH range is between 5.2 - 5.6 regardless of beer style!
  • A high residual alkalinity often requires the addition of acids or acidulated malts to get the mash pH down into the optimal range for saccharification
  • Predicting the exact mash pH is difficult regardless of knowing the residual alkalinity and recipe
  • Therefore ALWAYS measure the pH during the mash and adjust accordingly. Cheap pH meters or pH strips work just fine!
  • Always measure pH at room temperature (20-25C or 68-77F) or it's going to be incorrect, even if the pH meter has automatic temperature calibration (ATC). Most electrodes can't handle mashing temperatures.
  • A low mash temperature (62-64C or 144-147F) requires a lower pH around 5.2 to optimize beta amylase activity
  • A high mash temperature (70-72C or 158-162F) requires a higher pH around 5.5 to optimize alpha amylase activity. Alpha amylase also requires Ca2+ ions.
  • That's it. The mash is not rocket science!

The reason why residual alkalinity is so important on the brew day is because pH is important! Everything the mash is all about is the saccharification of starch into simpler and smaller sugars by the different enzymes naturally present in the malt. The brewer's only, and very simple, job during the mash is really just to manipulate the activity of enzymes, mainly alpha and beta amylase, by ensuring a proper pH and temperature (and also proper recirculation) that is optimal for these enzymes to do their work effectively. That's it! It's not rocket science, it's elementary school stuff! To ensure a proper mash efficiency the pH must always be between 5.2 - 5.6 regardless of beer style! If the pH is not within this range the mash efficiency will drop significantly and the beer will taste sour if the pH is too low, and too harsh if it's too high, especially if lots of boil hops are used. The grain and the saccharification process by itself will also lower the pH, but usually not enough. Exactly how much depends on the residual alkalinity and also the grain bill and recipe. If the brewing water has a high residual alkalinity, you most likely need to adjust the pH by either adding acid (usually lactic acid or phosphoric acid) or include acidulated malts in the grain bill to get the pH down into the optimal range. The grain itself also contains many different compounds with a significant buffering capacity, but it's really difficult if not impossible to calculate and predict the exact mash pH depending on the recipe. With pure water the pH can be calculated rather precisely using for example the Henderson-Hasselbach equation, but it's only useful with pure water. Therefore, always measure the pH using a pH meter or a pH strip 10-15 minutes into the mash and then adjust accordingly. I use a $20 pH meter and it's roughly on par with a professional lab-grade one we have at work. 0.1 precision is absolutely fine for home brewing.

The exact target pH depends on the mashing schedule. A highly fermentable mash profile such as that used for lagers and other light bodied beers, will aim to optimize the activity of beta amylase to primarily yield maltose and maltotriose. The optimal conditions for beta amylase activity is a temperature around 62-64C or 144-147F and pH around 5.2. For a big-body beer the mash profile should optimize alpha amylase activity to yield more dextrines and unfermentable sugars in the final beer. The optimal conditions for alpha amylase is a temperature around 70-72C or 158-162F and pH around 5.5. Additionally, alpha amylase is a metallo-enzyme and requires Ca2+ to function as opposed to beta amylase. Most beers are just fine with a medium-body profile that optimizes the activity of both enzymes, and for that I would aim for a pH between 5.3-5.4. There are of course other enzymes that are relevant, like beta-glucanase, phosphatases, proteinase, peptidases, but the high-quality malts available today are well modified and generally don't need other temperature "rests" to enhance mash efficiency or taste.

Mineral composition

TLDR

  • 5 different ions are the most important for brewing water. Those are: Calcium (Ca2+), Magnesium (Mg2+), Sodium (Na+), Chloride (Cl-), and Sulphate (SO42-).
  • Calcium (Ca2+) doesn't contribute with any desirable taste on its own, but has positive side-effects including increasing stability and clarity of the final beer, precipitates phosphates and is required by alpha-amylase. Always ensure a minimum Calcium (Ca2+) level of 30-40 ppm.
  • Almost always keep Mg2+ and Na+ levels low (0-30 ppm). The only exception is when you want a salty taste, then raise the Na+ level with table salt (NaCl).
  • When it comes to taste only Chloride (Cl-) and Sulphate (SO42-), and the ratio between them, is the most relevant
  • Chloride (Cl-) accentuates "fullness". Typical range is 0-250ppm.
  • Sulphate (SO42-) accentuates "dryness" and makes bitterness more crisp. Typical range is the same as with Chloride (Cl-), 0-250ppm
  • Never push both Chloride (Cl-) and Sulphate (SO42-) levels to more than 80-100 ppm at the same time. This can cause harsh and unpleasant flavors.
  • Add salts to adjust your water to match a target water profile. Common salts are CaCl2, MgCl2, MgSO4 (epsom), CaSO4 (gypsum), and regular table salt (NaCl).
  • Use brewing software like BrewFather to calculate exactly how much of each salt to add to hit a target, or suggested, water profile
  • (ppm is equivalent to mg/L)

Traditionally the local water source from a particular region was used as-is without any adjustments and the character of some beer styles originates partly also from the mineral content of the water from the particular region where the brewery invented the style centuries ago. Today, most breweries are in complete control of the mineral content of the water where they will both gather reports regularly about the source water and adjust accordingly using salts. When it comes to the taste of the water itself and how it suits a particular beer style the mineral composition is important. Minerals are dissolved in water as ions, which either have a positive (cations) or negative (anions) charge. Luckily we essentially only have to know about 5 different ions that are relevant to brewing water for beer, they are: Calcium (Ca2+), Magnesium (Mg2+), Sodium (Na+), Chloride (Cl-), and Sulphate (SO42-). The ratio of the latter two is very important, which we will come back to in a bit. Some would also include Potassium (K+), but it's only really needed in a very low amount for the yeast (typical range: 0.5-2.0 ppm), otherwise the taste is similar to Sodium (Na+) giving a salty taste. Both should generally just be kept low regardless of style (2-25 ppm). One beer style in particular that needs a lot of Sodium (Na+) though is the Gose. It needs to be salty, but most other styles hardly needs Sodium (Na+). Typical range is 2-25 ppm. Magnesium (Mg2+) has a minerally and even bitter taste in excess. Generally keep it low (0-30 ppm) since it contributes with no flavor that is relevant or supportive to beer.

Calcium (Ca2+), as mentioned, mostly impacts the alkalinity of the water together with Magnesium (Mg2+). The taste of Calcium (Ca2+) is not very distinct on its own. In high amounts though (120ppm or more) it will taste a bit like chalk, and, well, hard water. The real benefits of Calcium (Ca2+) is its side-affects on other things. There are many benefits of Calcium (Ca2+), which include improving stability and clarification of the final beer, it helps precipitate phosphates, and most importantly required for optimal alpha amylase activity during saccharification at higher mash temperatures (70-72C or 158-162F). Therefore, it's important that a minimum of 30-40 ppm or so is always present regardless of beer style, even with a low mash temperature. Typical range is 30-100 ppm, while most ales and generally anything but lagers should benefit from 60-70ppm.

Sulphate to Chloride ratio

Chloride (Cl-) and Sulphate (SO42-) levels and the ratio between them are the most important ions when it comes to taste. They directly influence the taste and mouthfeel of the beer and the amounts of each must be chosen carefully to match the style. In the end it's purely a subjective matter and up to the brewmaster to decide what (s)he wants to accentuate in the beer. But simply put, high Chloride (Cl-) levels accentuate "fullness", as well as body and sweetness/maltiness, while high Sulphate (SO42-) levels will make the beer dry and crisp, and supports bitterness well. The minimum threshold for both to affect the taste at all is around 50-60 ppm. Typical ranges for both is 0-250ppm. The overall level of both anions and the ratio between them is generally adjusted to match the beer style. A typical balanced Sulphate/Chloride ratio is between 0.8-1.5, whereas a ratio that suits more malty or "full" beers would be 0.5-0.7. For beers like west coast IPA's with a high level of bitterness it can be appropriate to raise both the level of Sulphate (150-250 ppm) and also increase the Sulphate/Chloride ratio to as high as 4-9 by lowering the Chloride level accordingly. Regardless of the ratio, it's very important that both the Sulphate and Chloride levels are never elevated at the same time (max 100ppm for both), because this can lead to harsh and unpleasant flavors. According to the book "Water: A Comprehensive Guide for Brewers" by John Palmer and Colin Kaminski here are some general guidelines:

  • 0-0.4: Too Malty
  • 0.4-0.6: Very Malty
  • 0.6-0.8: Malty
  • 0.8-1.5: Balanced
  • 1.5-2.0: Slightly Bitter
  • 2-4: Bitter
  • 4-9: Very bitter
  • 9+: Too bitter!

Personally, I like to think a bit differently and associate Chloride with "fullness" and Sulphate with "dryness" and not "malty" or "bitter", respectively. For example, in recent years the ever so popular heavily dry-hopped juicy and hazy New England IPA with a very low bitterness a very low Sulphate/Chloride ratio is in its right. By raising Chloride levels as high as 200-250 ppm while keeping Sulphate levels below detection threshold (50-60 ppm) it really makes the tropical juice shine. A good level of sweetness is important to support all the hops, so the "fullness" from the high levels of Chloride can really make it pop. I know the guys at Verdant are keen on high levels of Chloride for many of their world class juicy DIPA's and I personally do the same.

The mineral composition of your source water

It's very important to know the mineral composition of your source water before trying to adjust it. Gathering information about your particular source water can sometimes be tricky as it's not always readily available from all suppliers across the world. Contact them or check their website. I'm lucky that in my area I can just enter my address online and get a quality report including mineral content from the particular ground water pump station, but if that's not available to you, you are going to have to spend some money either getting a water sample analysed at a laboratory or buy a water examination kit yourself. In most cases, it's cheaper to just use bottled mineral water (mineral content is often written on the packaging) or in the long term even cheaper to just buy a small reverse osmosis system to produce almost completely demineralized water at home and then add salts to get to where you want. I've got my RO system for around 100$, so it quickly pays for itself after only a handful of brews compared to bottled water. Since I know the mineral content of my source water, I usually dilute with 40-70% RO water depending on the beer style and matching water profile. It's necessary since my source water is very hard, so I have to get Ca2+ levels down to be able to increase both SO42- and Cl- levels with salts. You can also use 100% RO water if you don't know anything about your source water, but then you must add stuff like baking soda or limescale to increase the alkalinity to an acceptable level. One noticable advantage of using 100% RO water is that you might be able to hit the optimal pH range (5.2 - 5.6) by dialing in the bicarbonate level instead of having to buy both a pH meter and acids.

Adjusting the mineral composition using salts

To adjust the composition you can simply add salts to increase the levels of particular ions. Normally those salts are CaCl2, MgCl2, MgSO4 (epsom), CaSO4 (gypsum), and regular table salt (NaCl). Increasing the alkalinity is also possible using baking soda (Sodium Bicarbonate). As salts are composed of a cation-anion pair, it's impossible to increase the concentration of a single ion at a time without also increasing the concentration of another one. Therefore a combination of salts is usually added to get near the target water profile. There is absolutely no difference between raising the level of a single ion, for example sulphate, using different salts like epsom or gypsum except that they raise different cation levels, here Mg2+ and Ca2+ respectively. So there is some freedom of choice depending on your source water. It's also important to mention that the water profile is only a target. Measuring the exact mineral composition of the finished beer is probably only done by macrobreweries with strict quality control. Regarding Calcium it's best to add it during the mash (by now you know why), and it's also possible to add particular salts like slaked lime (Calcium Hydroxide) or chalk/limestone to increase the concentration of Calcium alone without affecting other ions. The tradeoff though is that slaked lime will directly increase pH and limestone is not easily dissolved and might only be possible to dissolve during the boil.

So how do you calculate exactly how much to add to hit your target? Well, that's just too simple nowadays. You can calculate it based on the molarmasses of each salt and adjust to the batch size, but pretty much all brewing software can do that for you now, so let's skip the math. I use BrewFather for everything now, which is just amazing in every aspect. It can suggest water profiles based on the style of your choosing, display the sulphate/chloride ratio, estimate acid additions, both for the mash and sparge water. You can select which salts you have in stock and it will calculate exactly how much to add of each salt to hit the target profile. What more do you need? Other free options include Brewer's friend - Mash Chemistry and Brewing Water Calculator and John Palmer's (author of How to Brew) smart phone app.

Conclusion

Water chemistry might seem scary, but at some point in your home brewing journey there is just no way around it. This is just a summary of the information I've gathered over the years and I hope you've learned something! I've tried to go into the details, but also keep it simple for those who just want to know enough about what to do in practice. Let me know in the comments if I've missed something or if you just completely disagree with something.

Højt skum!

References