Ask Mr. Wizard

The Low Down on Water Softeners for Brewing


Byron Hovey, Carolina Beach, North Carolina asks,

I need some advice on treating brewing water for all-grain brewing. I lived in an area of very soft water, but now I've moved to an area of high alkaline, very hard water. I installed a water softener in my house and now my water analysis shows that the PH is 7.3, the total alkalinity is 226 ppm, and the calcium, magnesium, and sulfates are all low. The softener Didn’t raise the sodium and chloride too high, (Na+ 88 ppm and cl- 71). I understand that calcium is needed for any style of beer and that mash PH should be about 5.2. I've thought of diluting the water with distilled water to reduce alkalinity and adding minerals back. Should I measure the PH of the mash and adjust it with lactic acid if necessary?


I want to recap a few things before suggesting a solution to your water woes. Before your move, you had soft water that worked well for brewing. Now you have water from a softener with a high pH. I will save pH for last because that is the least of your worries.

For starters, what does “soft” refer to when discussing water? The term “soft” is generic and simply means that water is low in calcium and magnesium. When water containing a mix of calcium, magnesium, and bicarbonate (the soluble form of carbonate), is boiled or held hot for an extended time, carbonate crystals are deposited according to the following reaction:

2Ca+2 + 2HCO3 CaCO3(s) + H20 + CO2(g) + Ca+2

2Mg+2 + 2HCO3 MgCO3(s) + H20 + CO2(g) + Mg+2

It is worth noting that the carbon dioxide gas formed in these reactions escapes into the air and helps drive this reaction; this is why these reactions do not have equilibrium arrows. Excess calcium and magnesium are shown to help illustrate the concept of permanent hardness.

The hardness removed by this reaction is called “temporary hardness,” and the calcium and magnesium that remains is termed “permanent hardness.” In other words, temporary hardness = total hardness – permanent hardness. The practical importance of this equation is that total and permanent hardness can both be directly measured, whereas temporary hardness is calculated by difference.

Brewers know that high carbonate water is not ideal for brewing; understanding the concept of permanent hardness is helpful and explains why it helps to add calcium sulfate and/or calcium chloride to this sort of water. This is why so many brewing recipes suggest adding a pinch of gypsum; too much calcium is unlikely to cause a brewing problem, but too little is not a good way to start the day.

Since most homeowners who also homebrew do more with water than brew beer, this hardness discussion oftentimes includes the topic of water deposits in the home. If you have water that contains temporary hardness (total hardness ≠ permanent hardness), you will end up with carbonate deposits in your water heater, and hard water, in general, results in soap scum. Homeowners will install water softeners in their homes to combat these two problems.

Softeners work by replacing calcium and magnesium with sodium using an ion-exchange column (the column is usually filled with polystyrene sulfonate resin beads). It is important to note that softeners do not remove carbonates, and they do not increase chloride levels in the water because the brine used to displace calcium and magnesium ions from the ion-exchange column is flushed as part of the regeneration cycle. Since water softeners are not exactly cheap to purchase, install, and operate, most homeowners only purchase softeners when water hardness is a problem. And problematically hard water usually originates from limestone aquifers and is rich in carbonates.

There are two important take-home messages from the discussion above:

First, brewing water with too little permanent hardness can be remedied by adding calcium sulfate (gypsum) and/or calcium chloride. Some brewers like to add some magnesium sulfate (Epsom salts), but calcium is absolutely required for mash enzymes and is more effective at adjusting mash pH than magnesium . . . not to mention that too much magnesium tastes very bitter and may cause GI tract “issues.” Second, water softeners produce water with essentially no hardness, and softeners do not remove carbonates. This means that softened water requires further treatment (calcium is required for brewing), and also means that softened water is usually high in carbonates because, as mentioned above, most hard water comes from limestone aquifers.

Although modern brewing technology is, in many cases, extremely different from state-of-the-art methods from the past, there are plenty of breweries in the world that continue to use these older methods. Why? Because replacing capital equipment is expensive, and modern technology can be very difficult to justify if the investment is not required to replace equipment that has ceased to function. This is why many breweries continue to use older methods of water treatment that are based on “wet chemistry” conducted on a large scale.

While effective, these older methods require a fair amount of chemistry knowledge to understand, and a fair bit of analytical capabilities to monitor and control. The handy thing about water treatment is that reverse osmosis (RO) has really changed how drinking and process water is demineralized. RO water desalination was developed in the 1950s at UCLA and at the University of Florida, and became commercially viable in the early 1960s when the Loeb-Sourirajan Membrane was developed by scientists at UCLA.

Today, RO water treatment is used by municipalities to produce drinking water from seawater, and is also used at the point-of-use to produce drinking water for home consumption and for sale at grocery stores. RO systems require soft water and are installed downstream of softeners. This makes them an attractive thing for homeowners to buy after a softener is installed.

Note: Distilled water is very similar to RO water. The primary difference in the two has to do with how the water is demineralized; distilled water is boiled to remove minerals, whereas RO water uses a membrane. Both systems produce mineral-rich water as a waste stream. Since distillation requires far more energy than RO filtration, distilled drinking water is far less common than RO drinking water.

Using RO water makes adjusting water very easy. With RO water you don’t have to change your mineral additions based on how your water changes during the course of a year (most people are surprised by how inconsistent tap water actually is), and you don’t have to explain the details of your water chemistry to another brewer when exchanging recipes. The latter can be very challenging, and is probably why many authors resorted to the old “add a tsp. of gypsum” advice.

If you want great brewing water, tailored to the types of beers you want to brew, without learning any more than you currently know about water chemistry, use RO water. Either buy it at the store or install an RO system and be done with it. Seriously, that is the way to go. When using RO water, you must add minerals. I like using a combination of calcium sulfate, calcium chloride, and a touch of sodium chloride. If you are using roasted malts, sodium bicarbonate or calcium carbonate (the former, baking soda, is easier to use because it is water soluble without having to adjust pH) helps balance the acidity of these malts. I prefer adding roasted malts after mashing is complete, and I don’t worry about how they affect pH.

And that brings up the last question you raised; water pH. This value, in and of itself, does not mean anything to brewers. The pH values that matter in wort production are mash pH (pH 5.2–5.4 is the ideal range), wort pH flowing from the mash tun (anything from pH 5.2–5.8 is great, and pH 6.0 for the last runnings is tolerable), and wort pH before the boil (I like pH 5.2–5.4, and nothing greater than pH 5.6). If you find that you need to acidify mash or wort, lactic acid or phosphoric acids are easy to use. You can also add calcium since it reacts with malt phosphates and amino acids to decrease mash and wort pH. And if you need to bump the pH up, baking soda is really the easiest thing to add. Don’t worry about the sodium since you are really not adding much at all.

I hope this helps to remove some of the hardness associated with water chemistry, arguably one of the most confusing of brewing subjects!

Response by Ashton Lewis.