Flat Kombucha: What Causes It and Is It Okay to Drink?

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Although it's fine to drink, flat kombucha can be a homebrewers biggest nemesis. Carbonating kombucha is a bit tricky at first, but with a good understanding of what causes kombucha to be fizzy, your homemade booch is more likely to come out carbonated and delicious.

Is Kombucha Supposed to Be Fizzy?

Generally speaking, kombucha should be a fizzy drink, yet there are reasons why your kombucha isn’t coming out very bubbly. When brewing kombucha, the yeasts in the brew eat the sugars and produce alcohol and carbon dioxide, which is what creates carbonation.

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Carbonation during the first fermentation

The kombucha is covered with only a cloth during the first fermentation, meaning the carbon dioxide (CO2) can escape. This is why we do a second fermentation in airtight bottles trapping the carbon dioxide and creating fizzy kombucha.

What Causes Flat Kombucha?

Carbonation is simply adding CO2 gas to a beverage, giving it a bit of sparkle and fizz and somewhat of a tangy taste. This can be obtained through forced or natural carbonation. Because most kombucha gets its bubbles naturally, there’s always something that can go awry.

Some of the reasons your kombucha has little to no fizz include the following:

  • Using the wrong bottles
  • Incorrect first fermentation time
  • Cutting the second fermentation too short
  • Not stirring your kombucha before bottling
  • Leaving too much air in the bottles
  • The temperature is too cold
  • Not adding enough sugar or fruit
  • Filtering the kombucha before bottling
  • Burping your kombucha too much

Is Kombucha Still Good if It’s Flat?

Flat kombucha is perfectly fine to drink. If your kombucha doesn’t taste as it should, smells strongly of vinegar, or if the SCOBY particles have changed colors, don’t drink it. However, the amount of carbonation doesn’t signify anything dreadfully wrong.

Does Flat Kombucha Have Different Health Benefits?

Flat kombucha still has the same nutritional components as carbonated kombucha, meaning you can reap the same benefits. Carbonation is just an added effect that some people prefer.

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Carbonated kombucha

Homebrewed kombucha does not always have as much carbonation as store-bought kombucha because, many times, commercial kombucha contains forced carbonation, making it bubblier.

If your body doesn’t digest carbonation well, flat kombucha is an optimal choice.

9 Ways to Ensure You Brew a Carbonated Batch of Kombucha

While some people like to drink kombucha with less carbonation, most like at least some fizziness. Here are some ways to ensure your kombucha is fizzy:

  1. Use fermentation bottles to get the right amount of carbonation. These flip-top bottles are designed to trap in air and withstand pressure so they don’t explode.
  2. You need the goldilocks amount of time for your first fermentation. Not too long, not too short, but just right. Your booch must brew long enough for the bacteria and yeasts to build up but not so long that it becomes too vinegary-tasting.
  3. Allow for a longer second fermentation. Typically, a second fermentation process lasts between 3-10 days, but this could vary depending on the temperature of your house and the amount of sugar it contains. If your kombucha doesn’t seem fizzy enough, extend the second fermentation.
  4. Stir your kombucha before bottling. When you pour kombucha straight from the fermentation jug into the bottles, the yeast and bacteria will not be evenly distributed, so stirring before you pour is always a good idea.
  5. Only leave 1-2 inches of head space at the top of the bottle. While you should always leave a little head space as a buffer for the pressure, leaving too much will mean that the CO2 stays in the air in that space and does not enter the kombucha tea.
  6. Make sure your fermentation station is warm enough. Fermentation drastically slows down when temperatures are low. Room temperature should be fine for brewing kombucha, ensuring it is kept in an area between 68 and 78 degrees Fahrenheit.
  7. Make sure there is enough “food” for your kombucha. Adding fruits, sugar, or honey isn’t just for flavor. They act as “food” for the yeast and are the catalyst for creating carbonation during the second fermentation.
  8. Don’t filter out the sediment. The yeast sediment is necessary for decent carbonation.
  9. Don’t over-burp your bottles of kombucha. If you’re new to brewing, burping your bottles means opening them ever-so-slightly to remove excess pressure. However, if you are doing this too much, you are probably also letting out some of that good carbonation. Let your second fermentation sit for 2-3 days before burping it.


Margaret has been drinking kombucha for its health benefits since 2010. Not only does she love drinking it, but she also enjoys brewing her own homemade booch. Her favorite combination so far is mint-strawberry, but she is always experimenting with new recipes.

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