Many municipal water sources use chlorine or chloramines to treat and disinfect water to ensure safe drinking. I have town water where I live so I know it contains chlorine. Chlorine can be removed from water by pre-boiling or by letting it sit out in the kettle with the lid off for 24 hours. Chloramines are more difficult to remove and require carbon filtration or treatment with sodium metabisulfite or potassium metabisulfite.
Why Chlorine and Chloramine Is Bad for Brewing
Chlorine and chloramine can produce chlorophenols in beer that contribute plastic-like or medicinal off-flavors. More delicate styles, such as NEIPAs are more susceptible to these types of off-favors.
The good news is both chemicals can both be easily eliminated with Campden tablets. Campden tablets are typically used for winemaking and come in two forms, sodium metabisulfite or potassium metabisulfite. Both will remove chlorine and chloramine almost instantaneously.
The alternative solution is to buy distilled/RO (reverse osmosis) water that is free of minerals and chemicals. I prefer to use RO water and build my own mineral profile with a clean slate, it’s just not always convenient to buy jugs of water.
How to Use Campden Tablets
Add 1 crushed Campden tablet per 20 gallons of brewing water. I use half a tablet for 5-gallon batches (about 9–10 gallons of starting water). Campden can be easily cut in half with a knife and crushed with a spoon or broad side of a knife. Add directly to your water, stir, and let sit for a few minutes before proceeding with your brew day. It’s as easy as that! If I didn’t make it clear, Campden should only be added to fresh water. Do not add in conjunction with any other brewing ingredients.
If you’re unsure if your water contains chlorine or chloramine, it does not hurt to add Campden as a precautionary measure. Call your town or city water supplier to provide more information on your water.