Remove chlorine from tap water

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Municipal water is treated with chlorine compounds (either chlorine or chloramines) at the treatment plant in order to make sure the water is protected from hazardous bacteria and other pathogenic organisms.[1][2] Even if the water is not initially treated with chloramines, they are formed from chlorine as a product of the disinfection process.[3] Water treatment plants may also switch between using chlorine or chloramine without warning.[4][5] So, generally speaking, tap water may contain chlorine and/or chloramines.[6] The residual chlorine level in tap water can vary by location and over time, but it is generally below 4 mg/L Cl2.[1][7][8][9][10]

Why is chlorine a problem for brewing? Given the opportunity, the chlorine compounds in tap water will react with phenolic compounds in the wort, resulting in the formation of off-flavors (chlorophenols).[11][12][13][4][14][15][16][17][8] These flavors are harsh, medicinal, fishy, pond-like, plastic-like, or Band-Aid-like, and are detectable in beer at very low concentration.[11][18][4][14][19][16] Therefore, it is recommended to remove chlorine compounds from the water before brewing.[11][12][10] Interestingly, some people are extremely sensitive to sensing chlorophenols, while others are virtually "taste-blind" to them.[11][10] Be aware that chloramines are more difficult to remove than chlorine by some methods because they are less volatile and less reactive.[6][4][20]

It may be wise to verify that the chosen method for dechlorination has been successful.[18] Inexpensive test kits for free chlorine and total chlorine are available from aquarium stores or laboratory suppliers.[4] Free chlorine tests detect only chlorine, while total chlorine tests also detect chloramines.[4] Liquid test kits are preferred rather than test strips since they tend to be more sensitive at low concentrations.[10]

Sulfite for chlorine removal[edit]

Both chlorine and chloramines can be neutralized using a small amount of sulfite (from sodium metabisulfite or potassium metabisulfite).[13][18][2][10] "Campden tablets" are convenient for this purpose, since the dosage doesn't need to be exact.[21] Alternately, metabisulfite powder can be used, if you have an appropriate scale for measuring small amounts. It is customary to add more sulfite than is theoretically needed, to be certain that 100% of the chlorine is neutralized.[2][21] Add the sulfite after heating the water to strike temperature. The reaction occurs instantly, although stirring is required to ensure good mixing.[18][2] Any residual sulfite is oxidized to form sulfate during the brewing process — the sulfate and other ion contributions can generally be ignored since they are so small.[18][10] Here is our calculator for determining the amount of sulfite recommended based on your sulfite product and water characteristics. It rounds up to the nearest half tablet.

Sulfite dosing calculator

or
or
mg
US gallon(s)

mg/L Cl2
15%

Result:
0.5 tablets should be crushed and mixed into 10 US gallon(s) hot strike water.

FYI, this adds 2 mg/L sodium and 5 mg/L SO2, which becomes 7 mg/L sulfate.

Carbon filtration for chlorine removal[edit]

Running the water through an activated carbon filter is a good way to remove chlorine and many other organic contaminants.[11][4][22][13][15][23][16][2][10] A special catalytic carbon filter can be used for water that contains chloramines, because chloramines are not as easily removed by a typical carbon filter.[6][3][10] In any case, a slow flow rate through the filter is critical to improving contaminant removal and extending the filter life.[4][22][10] The filter manufacturer may provide a recommended flow rate, or in some cases you can calculate it based on the the filter bed volume: Empty Bed Contact Time (EBCT) is the parameter for activated carbon systems.[4] EBCT = volume of the carbon filter ÷ flow rate. EBCT should be at least 2–3 minutes for chlorine and at least 8 minutes for chloramine.[4][22][10]

The flow rate through a standard under-sink (10-inch) activated carbon filter unit should be no greater than 1 gallon per minute to achieve good hypochlorite removal. Inserting a restrictor plate in the filter's water supply line with a 1/16-inch diameter hole should help achieve this. Smaller filters need slower flow.[10]

Other methods (not recommended)[edit]

Chlorine is very volatile and therefore it can be partially removed by exposure to air or heating.[4][13][10] This means that simply heating the water to strike temperature in an open kettle will drive off most of the free chlorine. However, it only takes very small amounts of free chlorine in brewing water to produce discernable chlorophenols in beer.[4] Also, chloramines are significantly less volatile and cannot be removed in this manner.[4][18] Therefore, it's not recommended for brewers to rely solely on heating or aeration for chlorine removal.

Ascorbic acid, like sulfite, can neutralize both chlorine and chloramines. However, we do not recommend using ascorbic acid to neutralize chlorine, because it has several drawback compared to sulfite.[10] Ascorbic acid costs more, it lowers the water pH, and the reaction with chlorine leaves behind dehydroascorbic acid, a reactive compound that will contribute to oxidation during mashing.[21]

See also[edit]

References[edit]

  1. ↑ a b Karim K, Guha S, Beni R. Comparative Analysis of chemical, physical and biological contaminants in drinking water in various developed countries around the world. J Water Resour Prot. 2020;12(8):714–728.
  2. ↑ a b c d e FilmTec™ reverse osmosis membranes technical manual. Dupont website. Updated April 2020. Accessed October 2020.
  3. ↑ a b Scherer T, Johnson R. Filtration: Sediment activated carbon and mixed media. North Dakota State University website. Revised Feb 2022. Accessed online Mar 2024.
  4. ↑ a b c d e f g h i j k l m Palmer J, Kaminski C. Water: A Comprehensive Guide for Brewers. Brewers Publications; 2013.
  5. ↑ Water disinfection with chlorine and chloramine. Centers for Disease Control and Prevention (CDC) website. Last reviewed 2020. Accessed online March 2024.
  6. ↑ a b c Robinson B. How to remove chloramines from water. Fresh Water Systems website. 2020. Accessed online March 2024.
  7. ↑ Brandt MJ, Johnson KM, Elphinston AJ, Ratnayaka DD. Chapter 11: Disinfection of Water. In: Brandt MJ, Johnson KM, Elphinston AJ, Ratnayaka DD, eds. Twort's Water Supply. 7th ed. Butterworth-Heinemann; 2017:475–511.
  8. ↑ a b IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Chlorinated drinking-water; chlorination by-products; some other halogenated compounds; cobalt and cobalt compounds. International Agency for Research on Cancer; 1991. Accessed March 2024.
  9. ↑ Continuous chlorination disinfection system: Operation, maintenance & monitoring guidance for small water systems. California Water Boards. 2018. Accessed online March 2024.
  10. ↑ a b c d e f g h i j k l m Brungard M. Water knowledge. Bru’n Water website. 2020. Accessed online March 2024.
  11. ↑ a b c d e Taylor DG. Water. In: Stewart GG, Russell I, Anstruther A, eds. Handbook of Brewing. 3rd ed. CRC Press; 2017.
  12. ↑ a b Kunze W. Hendel O, ed. Technology Brewing & Malting. 6th ed. VLB Berlin; 2019.
  13. ↑ a b c d Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
  14. ↑ a b Eumann M, Schildbach S. 125th Anniversary review: Water sources and treatment in brewing. J Inst Brew. 2012;118:12–21.
  15. ↑ a b Howe S. Raw materials. In: Smart C, ed. The Craft Brewing Handbook. Woodhead Publishing; 2019.
  16. ↑ a b c Narziss L, Back W, Gastl M, Zarnkow M. Abriss der Bierbrauerei. 8th ed. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2017.
  17. ↑ Horák T, Čulík J, Kellner V, Jurková M, Čejka P. Determination of chlorinated phenols in brewing liquor and beer using SPE. Kvasny Prumysl (Czech Republic). 2008;54(1).
  18. ↑ a b c d e f deLange AJ. Removing chloramines from water: Chloramines removal. MoreBeer website. 2013.
  19. ↑ Fix G. Principles of Brewing Science. 2nd ed. Brewers Publications; 1999.
  20. ↑ Disinfectants chloramines. Lenntech website. Accessed March 2024.
  21. ↑ a b c deLange AJ. Campden tablets (sulfites) and brewing water. Homebrew Talk website. 2012. Accessed March 2024.
  22. ↑ a b c Eumann M, Schaeberle C. Water. In: Bamforth CW, ed. Brewing Materials and Processes: A Practical Approach to Beer Excellence. Academic Press; 2016.
  23. ↑ Evans E. Mashing. American Society of Brewing Chemists and Master Brewers Association of the Americas; 2021.
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