How to Brew Water Kefir - a living, sparking drink

What Is Water Kefir?

Water kefir is a probiotic, naturally carbonated drink made by fermenting sweetened water with water kefir grains. Despite the name, these "grains" aren't grains at all—they're symbiotic cultures of bacteria and yeast (SCOBY) that look like small, translucent crystals.

When you add water kefir grains to sugar water with some minerals (from dried fruit, molasses, and a pinch of salt or bicarbonate), the microorganisms consume the sugar and produce:

• Probiotics: Beneficial bacteria for gut health
• B vitamins: Especially from the yeast
• Enzymes: That aid digestion
• Natural carbonation: From fermentation
• Trace alcohol: Usually around 0.5-1% ABV (slightly more with fruit in second ferment)

The result is a drink that's refreshing, slightly sweet, gently tart, and beautifully fizzy—nothing like commercial soft drinks. See more on the Microbiology below. 

Why Water Kefir?

Versatility: Unlike milk kefir, water kefir is dairy-free and vegan. The neutral base takes on any flavour you add—from simple lemon-ginger to elaborate fruit-herb combinations.

Living culture: Water kefir grains multiply. Start with half a cup of grains, and within months you'll have enough to share with friends or start multiple jars.

Quick fermentation: Unlike kombucha (which takes 1-2 weeks), water kefir is ready in 2-3 days. Perfect for impatient fermenters!

Low maintenance: Once you understand the rhythm, water kefir becomes second nature. Strain, bottle, flavour, repeat.

Probiotic benefits: Gut health, digestion, immune support—all the benefits of fermented drinks in a format that's accessible and delicious.

Getting Started: Sourcing Water Kefir Grains

You can purchase water kefir grains from The Fermentary along with full instructions for waking them up and getting started. We also sell ready-made water kefir in 1-litre pouches (first ferment) if you want to try it before committing to making your own.

Other sources:

• Friends who make water kefir (grains multiply, so people always have extras)
• Online fermentation communities
• Health food shops

Activating new grains: If you've just received grains (especially if they've been dehydrated for shipping), they may need a few fermentation cycles to wake up fully. The first batch or two might not be very fizzy—that's normal. Keep feeding them, and they'll become more vigorous.

Seasonal Flavour Combinations

Summer:

• Strawberries + basil
• Peach + mint
• Watermelon + lime + chilli
• Mango + ginger
• Berries + lemon verbena

Autumn:

• Apple + cinnamon
• Pear + ginger
• Quince + star anise
• Plum + thyme

Winter:

• Citrus + rosemary
• Ginger + turmeric + black pepper
• Dried apricot + cardamom
• Blood orange + vanilla

Spring:

• Elderflower cordial
• Rhubarb + rose
• Lemon + lavender
• Cherry + mint

Troubleshooting

Grains aren't growing:

• Not enough sugar
• Water too cold (ideal temp is 20-25°C)
• Chlorinated water (use filtered)
• Not enough minerals (add molasses more frequently)

Kefir isn't fizzy:

• Not enough sugar for second ferment
• Bottles not sealed tightly
• Not enough time at room temperature
• Grains not active enough yet (give them more cycles)

Kefir is too sour:

• Fermented too long
• Too warm
• Too many grains for the amount of sugar/water
• Reduce fermentation time

Grains are slimy:

• Too much molasses or dried fruit
• Switch to just sugar and bicarbonate for a few cycles
• Rinse grains gently in filtered water

Bottles exploding:

• Too much sugar in second ferment
• Left too long at room temperature
• Cheap or damaged bottles
• Burp bottles daily if concerned, or refrigerate sooner

Kefir tastes like vinegar:

• Massively over-fermented
• Too many grains for liquid volume
• Still drinkable (use in salad dressings!) but reduce fermentation time next batch

Mould on grains:

• Contamination, possibly from metal tools or dirty equipment
• Discard affected grains (though if you have healthy grains elsewhere, they can continue)
• Sterilise all equipment

Caring for Your Grains

Going on holiday:

• Short break (up to 1 week): Make a batch and leave it in the fridge. Grains will slow down but be fine.
• Longer break (1 week - 1 month): Strain grains, rinse, and cover with sugar water (1 tablespoon sugar per cup of water). Store in fridge. They'll be sluggish when you restart but will recover.
• Extended break (1+ months): Dehydrate grains by spreading on a plate and air-drying completely (takes several days). Store dried in a sealed container at room temperature. Rehydrate in sugar water when ready to restart.

Excess grains:

• Share with friends (everyone loves free starter cultures!)
• Compost (they're great for the garden)
• Eat them (yes, really—they're probiotic and edible)
• Blend into smoothies
• Dehydrate and store as backup

Grains multiplying too fast: Remove some regularly. They should roughly double every 2-4 weeks in good conditions.

The Microbiology: What's Living in Your Water Kefir?

Water kefir grains harbour an incredibly diverse and complex microbial ecosystem. Scientific studies using both culture-dependent and metagenomic sequencing techniques have identified the specific bacteria and yeasts responsible for fermentation. Understanding what's in your grains helps you appreciate just how remarkable this living culture is.

Bacterial Composition

Water kefir grains typically contain approximately 10^8 colony-forming units (CFU) per gram of lactic acid bacteria, making them the dominant microorganisms in the grains.

Lactic Acid Bacteria (LAB) - approximately 70% of total bacteria:

The LAB are primarily Lactobacillus species, which produce lactic acid, give water kefir its characteristic tang, and create the polysaccharide structure of the grains themselves.

Most common species:

• Lactobacillus nagelii - Often the dominant species (sometimes representing up to 95% in some grain batches)
• Lactobacillus hilgardii - Produces the exopolysaccharides (dextran) that form the grain structure
• Lactobacillus casei/paracasei - Facultative heterofermentative, also found in fermented vegetables and dairy
• Lactobacillus harbinensis - Produces antifungal compounds; first discovered in Chinese vegetable fermentation
• Lactobacillus hordei/mali - Related species often found together in water kefir

Other LAB:

• Leuconostoc mesenteroides and L. citreum (approximately 10% of bacteria) - Produce CO2 and contribute to carbonation
• Lactococcus lactis - Sometimes present in smaller amounts
• Oenococcus species - Recently discovered, including a possibly novel species (Candidatus O. aquikefiri)

Acetic Acid Bacteria (AAB) - approximately 10% of total bacteria:

These bacteria produce acetic acid (vinegar), which contributes to the complex flavour profile, especially in longer fermentations or when oxygen is present.

• Acetobacter fabarum
• Acetobacter orientalis
• Acetobacter lovaniensis
• Gluconobacter species

Bifidobacteria - approximately 5% of total bacteria:

Recently discovered in water kefir grains using modern molecular techniques:

• Bifidobacterium aquikefiri - A proposed new species specific to water kefir
• Bifidobacterium psychraerophilum
• Bifidobacterium crudilactis

These are the same beneficial bacteria found in the human gut and are particularly prized for their probiotic properties.

Other bacteria - approximately 5%:

• Zymomonas mobilis - Recently found in significant amounts in some water kefir samples; an unusual bacterium that produces ethanol and CO2

Yeast Composition

Water kefir grains contain approximately 10^6-10^7 CFU per gram of yeasts. Yeasts are more abundant in water kefir than in milk kefir, which contributes to the higher alcohol content and more vigorous carbonation.

Most common yeasts:

• Saccharomyces cerevisiae - The same species as baker's and brewer's yeast; produces most of the alcohol and contributes to carbonation
• Hanseniaspora valbyensis - Often one of the dominant yeasts
• Dekkera bruxellensis (also called Brettanomyces bruxellensis) - Can be the dominant yeast in some grains; known for producing complex, slightly funky flavours
• Lachancea fermentati
• Zygotorulaspora florentina

Other yeasts found less frequently:

• Candida species
• Pichia species (including P. kudriavzevii, which can be dominant in some grains)
• Kluyveromyces species
• Zygosaccharomyces species

How They Work Together

This diverse microbial community functions as a stable symbiotic consortium—each species has a role, and they work together rather than competing:

The Lactobacilli (especially L. hilgardii and L. nagelii) produce the dextran exopolysaccharides that form the physical structure of the grains. Without these bacteria producing this polysaccharide "home," the grains wouldn't exist.

The yeasts break down sucrose and produce ethanol and CO2. The ethanol can then be metabolised by some of the lactic acid bacteria, and the CO2 creates carbonation.

The acetic acid bacteria convert some of the ethanol into acetic acid, adding complexity to the flavour and preventing too much alcohol from accumulating.

The various LAB species produce different organic acids, enzymes, and flavour compounds that create water kefir's complex, balanced taste.

Population dynamics: There are approximately 4-10 times more microorganisms living on the grains themselves than in the surrounding liquid. As the grains grow (increasing in mass during fermentation), the total microbial population increases.

Why Composition Varies

Different water kefir grains from different sources can have quite different microbial profiles. Factors that affect composition include:

• Origin: Where the grains came from originally
• Substrate: What you feed them (type of sugar, minerals, dried fruit)
• Temperature: Warmer temperatures favour different species than cooler
• Fermentation time: Longer fermentations allow acetic acid bacteria to become more prominent
• Oxygen exposure: AAB thrive with oxygen; LAB prefer less oxygen
• Your water source: Mineral content affects which species dominate

This is why your water kefir may taste slightly different from someone else's, even following the same recipe. Your grains have their own unique microbial fingerprint.

Health Benefits from This Diversity

The diverse microbial community in water kefir provides numerous beneficial effects:

• Probiotics: Multiple species of beneficial bacteria that support gut health
• Enzymes: Help with digestion
• B vitamins: Produced by both bacteria and yeasts
• Organic acids: Lactic acid, acetic acid, and others that support digestion and gut health
• Short-chain fatty acids (SCFAs): Beneficial metabolites that maintain intestinal barrier integrity
• Antimicrobial compounds: Some species produce substances that inhibit pathogenic bacteria

Studies have shown that water kefir consumption can increase beneficial gut bacteria (including Bifidobacterium, Lactobacillus, Firmicutes, and Bacteroidetes) while decreasing potentially harmful bacteria (like Proteobacteria and Enterobacteriaceae).

The Difference Between Water Kefir and Other Fermented Drinks

Kombucha:

• Uses a SCOBY (looks like a pancake)
• Ferments tea + sugar
• Takes 7-14 days
• Slightly more acidic
• Contains caffeine

Water Kefir:

• Uses grains (looks like crystals)
• Ferments water + sugar
• Takes 2-3 days
• Lighter, more neutral
• Caffeine-free

Milk Kefir:

• Uses different grains (look like cauliflower)
• Ferments milk
• Takes 12-24 hours
• Creamy, tangy, yoghurt-like
• Dairy (unless using coconut milk)

Ginger Bug:

• Wild fermentation (no grains)
• Uses ginger + sugar + water
• Takes 5-7 days to create, then 2-3 days per batch
• Ginger-forward flavour
• More unpredictable

Why This Matters

Water kefir connects me to the living world in a way that few other preserving practices do. These grains are alive—genuinely, actively alive. They grow, reproduce, respond to their environment, and if I feed them well, they make something beautiful and nourishing in return.

There's something profound about tending to a living culture. It asks for consistency, attention, and care. Miss a few days, and they'll let you know (they get sour). Rush them, and they won't carbonate well. But when you get into the rhythm—strain on Monday, bottle on Wednesday, new flavours constantly—it becomes a meditation, a practice, a relationship.

And the result is pure joy: opening a bottle of strawberry-basil water kefir on a hot summer evening, or ginger-turmeric in winter when you need warmth, or elderflower in spring when everything's blooming. You're not just drinking a probiotic beverage. You're drinking summer, or winter, or spring, captured by living cultures and your own attention to what's in season.

This is why I love water kefir. It's practical, it's delicious, and it's a daily reminder that some of the best things in life require care and patience.

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For more fermented drinks recipes including milk kefir, kombucha, and seasonal cordials, visit our recipe page. 

Purchase water kefir grains or ready-made water kefir here

This recipe is featured in both of my books "Ferment for Good" and "Wild Drinks"

Further Learning

To explore water kefir and fermented drinks:

Sharon Flynn - "Ferment for Good" and "Wild Drinks" My books! Both contain comprehensive water kefir instructions, troubleshooting, and seasonal flavour combinations developed over years of making award-winning water kefir at The Fermentary.

Sandor Ellix Katz - "Wild Fermentation" and "The Art of Fermentation" The fermentation bibles. Sandor covers water kefir in the broader context of fermented beverages globally. His approach emphasises intuition and experimentation.

Pascal Baudar - "The Wildcrafting Brewer" Focuses on wild fermentation and foraged ingredients for drinks. Excellent for developing creative water kefir flavours using local, seasonal, and foraged ingredients.