Water kefir is one of the easiest home ferments going: a light, naturally fizzy, gut-friendly drink made from nothing more than sugar water and a spoonful of living grains. It's ready in a day or two, costs almost nothing, and the grains keep multiplying, so one batch leads to the next.
The two things to get right are keeping the grains well fed and healthy, and treating the fizzy bottling step with care, because sealed bottles build real pressure. The recipe is below, with the safety and how it all works underneath it.
How to Make Water Kefir: A UK Beginner's Guide
Makes About 1 litre; 1 to 2 days to ferment, plus 1 to 2 days for the fizz
Makes
About 1 litre; 1 to 2 days to ferment, plus 1 to 2 days for the fizz
Ingredients
For the ferment
Optional mineral booster (pick one, if the grains are sluggish)
For the fizz (per 500ml bottle)
Method
- 1
Dissolve the sugar fully in a little warm dechlorinated water, then top up to 1 litre with cool water. It should be at room temperature before the grains go in.
- 2
Add the grains, and a mineral booster if using, to a glass jar. Cover with a cloth or kitchen paper and a band, not a sealed lid.
- 3
Leave at room temperature, ideally 20 to 25°C and out of direct sun, for 24 to 48 hours. Taste from 24 hours, and pull it when it's lightly sweet with a gentle tang.
- 4
Strain through a plastic or nylon sieve into a jug, and set the grains aside. Don't rinse them, as that strips the film that keeps them healthy.
- 5
Start the grains on a fresh batch straight away, or pop them in some fresh sugar water in the fridge to pause them.
- 6
For fizz, pour the strained kefir into pressure-rated flip-top bottles, add your juice or fruit, leave a couple of centimetres of headspace, and seal.
- 7
Leave the sealed bottles at room temperature for 24 to 48 hours to build the fizz, burping them once a day, then refrigerate. Read the safety note below first.
- 8
Chill fully before opening, and open cold and slowly over a sink.
Cook’s notes
- Timings: about 10 minutes of hands-on work, then 1 to 2 days to ferment and 1 to 2 days for the fizz.
- Safety, the fizz step: a sealed second ferment builds real pressure and glass can shatter. Use sturdy flip-top bottles made for carbonation, burp them once a day (more often in warm weather), leave headspace, and refrigerate as soon as they're fizzy. Stand the bottles in a box or cool bag while they carbonate, and open them cold, slowly and pointed away from your face.
- Feed the grains, don't starve them: they eat the sugar, so change the sugar water every 24 to 48 hours even if it looks quiet. Never rinse them, and keep reactive metal away.
- Use a mineral-rich sugar. The grains need minerals to thrive, so unrefined sugars, or white sugar with a little molasses, keep them strong. Never use honey, as it harms the grains.
- Second-ferment flavours: lemon and ginger, a splash of apple, grape or elderflower cordial, or berries. The extra sugars are what feed the fizz.
- Taking a break: put the grains in fresh sugar water in the fridge, which holds them for a few days up to about three weeks, then give them a batch or two at room temperature to wake up.
What you’ll need
- Glass jar (about 1.5 litres)
- A cloth or kitchen paper, and a band
- Plastic or nylon sieve, keep reactive metal away from the grains
- Pressure-rated flip-top bottles, for the second ferment
Troubleshooting
The grains aren't multiplying or look lifeless.
Switch to a mineral-rich sugar and properly dechlorinated water, add one mineral booster like a dried fig, and feed them every 24 to 48 hours. Chlorine, mineral-poor water and heat all hold them back.
There's no fizz.
The fizz only comes from a sealed second ferment. Bottle the strained kefir with a little sugar or juice in a pressure-rated bottle, and check the seal.
It's gone too sour.
It fermented too long or too warm. Give it less time and somewhere cooler, and start tasting at 24 hours.
The liquid has turned slimy or ropey.
The grains are over-mineralised or out of balance. Stop adding any boosters, and if it doesn't recover, restart from backup grains.
The second ferment stayed flat.
Check the bottle's seal or gasket, add a touch more sugar or juice, and keep it a little warmer, but carry on burping it daily.
More about water kefir
What the grains are. Water kefir grains, sometimes called tibicos, aren't a grain at all. They're small, translucent, jelly-like clusters, a living community of bacteria and yeast held together in a scaffold of sugar and minerals.
How the ferment works. The yeasts and bacteria feed on the dissolved sugar and, as they do, produce the tang, the living cultures and the carbon dioxide that turn plain sugar water into a light, slightly tart drink.
Why two ferments. The first ferment, open with the grains, builds the culture and the flavour. The second ferment, sealed with the grains removed and a little sugar or juice added, traps the carbon dioxide to make the natural fizz.
Why minerals matter. The culture needs minerals to stay strong and multiply, which is why mineral-rich unrefined sugar, filtered or spring water, and small boosters like dried fruit keep the grains thriving, while chlorine and heavily stripped water hold them back.
A living, reusable culture. The same grains brew batch after batch indefinitely with regular feeding, so one starter can keep a household in fizzy drinks for the long term, in the same wholesome spirit as our other live ferments.
Staying safe with the fizz
The sealed second ferment builds real pressure as the yeast makes carbon dioxide with nowhere to go, and left too long a bottle can over-pressurise and even shatter. Always use sturdy bottles made for carbonation, flip-top or screw-top with thick glass and a good gasket, never thin glass or an ordinary jar. Burp the bottles once a day, more often in warm weather, leave a couple of centimetres of headspace, and don't overload them with sugar. Refrigerate as soon as they're fizzy, stand them in a box or cool bag while they carbonate so any blowout is contained, and open them cold, slowly and pointed away from your face.
Frequently asked questions
Written by
UK Homesteading Team
Editorial team
The UK Homesteading editorial team, offering UK-specific, evidence-led guidance on growing, keeping, preserving and the law.
