Water and chlorine
Tap water carries chlorine to kill microbes, and it doesn't spare the good ones. For a brine, use filtered, spring or rested water.
4 min read First steps Reviewed October 26, 2026 18 facts, each with its source
Why chlorine matters
Tap water is disinfected with chlorine or chloramine, and both can kill good bacteria1. In a ferment, the bacteria you want are exactly the ones the vegetables bring, so the water shouldn't make their job harder.
That's why several guides ask you to remove the chlorine, chloramines and fluoride from the water before fermenting2, and prefer filtered or spring water3. Oregon State University's kimchi recipe asks the same for its brine: non-chlorinated water, such as spring or filtered4.
Not all of them are that strict. The University of Illinois, in its sourdough guide, says tap water is usually fine, and that trouble comes with very hard or heavily chlorinated water5. Fervida takes the cautious option, because it costs little: for a brine, chlorine-free water.
What to do with tap water
It depends on what your water utility disinfects with. It usually says so on its website or through customer service.
| If your water has | What to do |
|---|---|
| Chlorine | Filter it, or let it stand overnight in an open pitcher |
| Chloramine | Use filtered or spring water |
| You don't know | Filtered or spring water: it covers both |
For chlorine, a filter or a pitcher left to stand overnight works6. Chloramine doesn't leave as easily: with it, the guides ask for spring or filtered water7. If you use a pitcher or faucet filter, check its specifications to make sure it removes chloramine.
Hard and soft water
Hard water carries a lot of calcium and magnesium. The guides treat it as a matter of color and texture, and it shows in the jar. The University of Minnesota asks for soft or distilled water for brines, because the minerals in hard water can discolor produce or change its texture8. The NCHFP lists hard water among the causes of dark pickles, and its fix is to use soft water9.
If your water leaves a lot of scale in the kettle and your pickles come out dark, try a bottled water with low mineral content.
Bottled, well or distilled
- Bottled: it works. Check the label for where it comes from and that nothing chemical has been added10.
- Well water: it can be used, but have it tested first11.
- Distilled: here the guides disagree. The University of Illinois says not to use it12; the University of Minnesota accepts it for brines8. For vegetables, if it's what you have, you can use it. For water kefir, don't (more below).
Water in a brine
In a brine, the salt is worked out on the water: 1% is 10 g per liter13. Weigh the water, or measure the liters with a marked jug, and let the calculator do the rest.
When sauerkraut doesn't make enough juice to cover itself, the NCHFP tops it up with boiled and cooled brine14. Boiling it and letting it cool before adding it is what its recipes say, and it's what Fervida does.
For kombucha, the water must be clean and potable15, and the part that steeps the tea is heated to 160–170 °F (71–77 °C)16.
Water kefir, the other way around
Water kefir is the exception. Its grains need minerals, so a review cited by British Columbia's health authorities advises against reverse osmosis, carbon-filtered and distilled water, and against tap water with chlorine or fluoride17. And hard water, with more calcium and magnesium, helps the grains grow18.
For water kefir, the simplest choice is a spring or mineral water with some mineral content. Its own guide covers the rest.
Where every number comes from
Every number in the text leads to its figure: the exact sentence from the official guide it comes from, in its own language.
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1
Tap water carries chlorine or chloramine, which can kill good bacteria
“Tap water is usually treated with chlorine or chloramine, which can kill good bacteria.”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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2
Chlorine, chloramines and fluoride in tap water must be removed before fermenting
“Tap water usually contains chlorine, chloramines and fluoride that must be removed before culturing.”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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3
Filtered or spring water is preferred
“Filtered water or spring water are preferred.”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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4
Non-chlorinated water, such as spring or filtered
“non-chlorinated water, such as spring or filtered”
Oregon State University Extension Service · Preserving Foods: Kimchi Basics (SP 50-1007, March 2020) · read on October 20, 2026
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5
Tap water is usually fine; very hard or heavily chlorinated, it may not ferment well
“Tap water is usually fine, but if the water is very hard or heavily chlorinated, the starter may not ferment well.”
University of Illinois Extension · Sourdough Bread: 101 (modified December 2025) · read on October 25, 2026
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6
To remove chlorine: a filter, or a pitcher left to stand overnight
“To dechlorinate tap water, use a water filter or fill a pitcher of water and let it stand overnight.”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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7
With chloramine, spring or filtered water is best
“If water is treated with chloramine, it is best to use spring or filtered water.”
University of Illinois Extension · Sourdough Bread: 101, Sourdough Starter Recipe and Sourdough Recipes #1-3 (modified December 2025) · read on October 25, 2026
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8
Soft or distilled water; hard water can discolor produce or change its texture
“Soft or distilled water for produce that is fermented using a wet brine. Minerals in hard water can discolor produce or cause texture changes.”
University of Minnesota Extension · Preserving food at home: Fermentation (reviewed 2026) · read on October 25, 2026
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9
Dark pickles from minerals in hard water: use soft water
“Dark or discolored pickles. (If brass, copper or zinc utensils and brining equipment were used, do not use pickles.) 1. Minerals in hard water. 1. Use soft water.”
National Center for Home Food Preservation (USDA, University of Georgia) · Causes and Possible Solutions for Problems with Fermented Pickles · read on October 26, 2026
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10
If it's bottled, check that it's free of chemicals
“If using bottled water, check the source to be sure it is free of chemicals.”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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11
Well water can be used, but have it tested first
“Well water can be used but have it tested for contaminants prior to use.”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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12
Don't use distilled water
“Do not use distilled water.”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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13
1% in brine is 10 g per liter
“1% solution = 10 g / L liquid”
UC Master Food Preservers, Inyo-Mono · Brine Math Made Easy · read on October 20, 2026
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14
To top up sauerkraut, boiled and cooled brine
“If juice does not cover cabbage, add boiled and cooled brine (1-1/2 tablespoons of salt per quart of water).”
National Center for Home Food Preservation (USDA, University of Georgia) · Sauerkraut · read on October 20, 2026
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15
Kombucha: clean, potable water
“and clean, potable water.”
University of Georgia Cooperative Extension (National Center for Home Food Preservation) · Crafting Kombucha at Home: Frequently Asked Questions (2026) · read on October 20, 2026
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16
Kombucha: the tea water is heated to 160–170 °F
“Heat 4 cups of water to 160° - 170°F (use a food thermometer to check), and add the tea to steep for 2 minutes.”
National Center for Home Food Preservation (USDA, University of Georgia) · Kombucha Tea · read on October 20, 2026
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17
Water kefir grains need minerals: no reverse osmosis, carbon-filtered or distilled water
“As trace minerals are required by the kefir grains, use of reverse osmosis, carbon filtered, and distilled water was not recommended, as was use of tap water containing chlorine or fluorides”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.12: Kefir, milk and water (December 2024) · read on October 25, 2026
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18
Hard water helps water kefir grains grow
“both figs and hard water (containing more calcium and magnesium ions) promotes water kefir grain growth in comparison to other fruits lower in calcium and soft water.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.12: Kefir, milk and water (December 2024) · read on October 25, 2026