More than 90 percent of your finished beer is water, so whatever is in your source water ends up in your beer. While malt, hops, and yeast usually get the spotlight, water actually sets the limit for your beer’s flavor. If there’s an issue with your water, no amount of brewing skill can fix it later.
For years, Canadian brewers only had to deal with one disinfectant: chlorine. It reacts quickly, smells like a swimming pool, and goes away fast when water is exposed to air or heat. This made it easy to manage. Leaving tap water out overnight or boiling it before brewing usually got rid of the chlorine and prevented harsh, medicinal flavors.
But things have changed. Many municipal water systems in Canada, including big ones in Ontario and other provinces, now use chloramine instead of chlorine. Chloramine is made by mixing chlorine with a little ammonia, and utilities like it because it stays active in the water system for weeks, not just hours. That same stability makes it much harder for brewers to deal with.
What Chloramine Does to Beer
Both chlorine and chloramine react with phenolic compounds in malt and hops, creating chlorophenols. Even tiny amounts of these can cause undesirable flavors and smells that brewers describe as medicinal, plastic-like, or like a Band-Aid. Since these flavors are noticeable at very low levels, even a little leftover chloramine can ruin the character of a pale ale or dull the hops in an IPA.
The problem is that chloramine acts differently than chlorine in your kettle. Since its chlorine atom is already attached to ammonia, chloramine is more stable and less reactive. This helps water treatment plants, as the disinfectant lasts longer in the pipes, but it’s a problem for brewers. Chloramine won’t boil off like chlorine, and leaving water out overnight doesn’t remove it either. It just stays in the water, ready to react with phenolic compounds during your mash or boil.
Why “Any Carbon Filter” Isn’t Good Enough Anymore
This is also where a lot of home and small-batch brewers get caught out. Standard activated carbon filters, the kind built into basic pitchers, fridge cartridges, and many entry-level under-sink units, were designed around chlorine’s chemistry. Chlorine reacts almost instantly with carbon and is neutralized on contact. Chloramine’s more stable, less reactive structure resists that same fast surface reaction, so a filter that removes chlorine perfectly well can still let a significant amount of chloramine pass straight through. A good breakdown of how standard carbon fails against chloramine explains that effectively neutralizing chloramine generally requires catalytic carbon, a carbon media manufactured differently from standard activated carbon so that it chemically breaks the chloramine molecule down rather than simply adsorbing it, along with enough contact time for that reaction actually to occur.
That distinction matters for anyone brewing with municipal water in a chloraminated region. It is not enough to know that your filter removes “chlorine, taste, and odor,” since that label doesn’t tell you anything about chloramine performance. It is worth confirming directly with your water supplier whether your system uses chlorine, chloramine, or a mix of the two, and then treating your brewing water accordingly.
Many homebrewers use Campden tablets, which contain potassium or sodium metabisulfite. You crush a tablet, stir it into your water, and it neutralizes both chlorine and chloramine in about twenty minutes. That’s why it’s a popular choice before brew day. The downside is that it only treats the water you remember to dose, and only at that time. Sparge water, cleaning rinses, ice, and any water added later all need their own dose, and if you get the ratio wrong, you might notice a faint sulfite taste.
A good catalytic carbon filter avoids this problem. Instead of treating each batch separately, it continuously treats all your water as it passes through—brewing liquor, sparge water, and rinse water are all handled the same way, with no extra steps plus added sulfites. For regular brewers, this ongoing protection is usually the best long-term solution, while Campden tablets can be kept as a quick backup.
This isn’t just something water filtration companies emphasize. The American Society of Brewing Chemists, the leading professional body for brewing science research, has presented technical findings on external flavor risks in beer production that identify chlorophenol as a defect formed directly from the reaction between chlorine and phenolic compounds in water, and note that poorly maintained carbon filtration in the brewery is itself a common contributor to the problem rather than a guaranteed fix.
The Bottom Line for Brewers
If your city has switched, or is switching, to chloramine, the old habits for dealing with chlorine won’t protect your beer anymore. Boiling or letting water stand won’t remove chloramine. Check with your local utility to see what they use, pick a treatment method that works for chloramine, and treat all your brewing, sparge, and rinse water the same way. Brewers often overlook water, but with chloramine now common in Canada, it’s something you can’t ignore.
