Of all the myriad of ingredients that go into the brewing process, water is the most important. The smorgasbord of chemical and mineral compositions playing off each other defines the beer style it makes up. Water treatment is a process that more brewers are taking into consideration as they look to create exciting new flavours. It can polish your final product and bring out subtle flavours, but it’s important to do your research beforehand, as some water treatment processes can remove important minerals.

Local water supply dictates the style of beer your homebrew will produce. For example, alkaline-high water such as the London supply naturally aids in brewing a dark porter/stout style beer. You are not limited to the type of beer best suited to your local supply. With new technology available, brewers have more control over their preferred results. There are many different techniques for water treatment, but this article is about Reverse Osmosis (RO) and how the process can help you achieve the brew you desire. The important thing is to know what you are aiming for. RO treated water naturally lends itself to certain beer types, such as Czech-style pilsner-lager. While the process may remove certain desirable minerals, these can be added at a later stage.

Here are some tips on what different minerals do for beer, which minerals you want to keep/remove, and how to achieve the balance you want when using RO treated water for your homebrew.

How does Reverse Osmosis work?

Reverse Osmosis is the process of passing feed water through a semi-permeable membrane to filter sediments and impurities out. Pure water comes out the other end, with all the contaminants passing out through the reject stream. This works by applying pressure on the feed water, forcing it through the membrane, and leaving 95-99% of the dissolved matter in the remaining feed water, which subsequently runs off as reject water.

Using RO water for your brewing mixture.

Reverse osmosis is a simple process of filtration, where water is fed through a membrane, leaving filtered water and the reject water containing all contaminants. The process removes dissolved solids and sediments. This results in water with a lower count of solids such as iron, fluoride, chlorine, and bicarbonate. Both low in minerals and low pH, RO treated water provides brewers with a good starting point for the process.

Imagine RO water as a blank canvas, leaving room for creative brewers to craft their beer into an artisan product, with flavours based on their preferences. Research your favourite beers, find out their locations, and experiment with your brews, or take the principles below and craft your unique beer.

Important minerals for beer.

RO water effectively removes a lot of the minerals and compounds in water, including chlorine and chloramine that completely ruin your batch. If you are looking for a beer with a complex or specific flavour profile, you may want to add more minerals in after. The following minerals can give your beer the flavour you want in tandem with the clean RO water:


Calcium is one of the most common hard water minerals found in tap water. It can present issues with fermentation and have a direct result on the clarity of the beer, so it's worth managing calcium levels. It has its practical uses too. Calcium can lower pH levels, enhance protein and prevent the beer from tasting ‘off’. If you are looking to make a lager, keep calcium to a minimum. A healthy amount is 50 to 110ppm.


Magnesium contributes to the hardness of water, to a lesser extent than calcium, and can give the beer a sour flavour in higher amounts (30ppm). Malt adds all the essential magnesium to the mix and so it’s not necessary to add more. Often brewers will add epsom Salts (Magnesium Sulphate) into their mixture if there is a high count of calcium.


Chloride, along with sulfate, contributes to the main flavour of the beer. Chloride is responsible for the fullness and sweetness of the flavour profile. For a malty beer, try a ratio of 150ppm chloride to 100 ppm sulfate.


Sulfate lends to hoppy bitter-tasting beers with its dry taste. Found sparsely in lagers, usually under 30ppm, and more so in ales. IPA’s and other highly hopped beers usually contain 150-300ppm. A good ratio to achieve a beer like this is 300 sulfates to 100 chlorides.


Sodium content helps to accentuate the malt flavors and adds to the texture of the beer. You can add salt to the mixture to increase sodium and chloride content. Too much will obviously affect the flavour of the beer, a safe amount of sodium is up to 100ppm.


Bicarbonate is integral to water treatment for brewing. Its alkalinity increases the pH of the mixture, and thus should be lower than 50 ppm for pale beers, up to 150ppm for amber beers, and up to 200ppm for dark beers that have high acidity roasted malts.

How can I increase levels of these minerals?

To get to the desired levels of minerals, you can add brewing salts. Most brewing salts are readily available online and sometimes at shops. These salts include calcium chloride, chalk, sodium chloride, baking soda, epsom salts, and gypsum. Different salts have different mineral properties. Calcium chloride adds calcium and chloride, epsom salts increase both magnesium and sulfate levels. Gypsum can increase calcium and sulfate levels, and sodium chloride increases sodium and chloride levels. Chalk and baking soda both serve to raise the pH. In the rare cases when this is a necessary step, baking soda is advised, as chalk doesn’t dissolve without other additional agents. Lactic or phosphoric acid can be used to lower the pH if needed.


Whether or not to use RO water for your homebrewing is a personal choice, best made on research on your local water supply. In most cases it’s advisable to have a degree of water treatment in your brewing process, as leaving excess minerals and sediments in the mix can lead to undesirable bitter, sour, and off flavours. RO treated water leaves you with purified water with neutral qualities. Untreated, the result with RO water can make a clean, light lager. If you are looking to make other types of beer, RO water gives you complete control over the process.