Kombucha Not Carbonating? 

Here’s How to Fix Flat Booch

If you’ve spent any time on Instagram or TikTok, you’ve probably seen the dramatic “kombucha explosion” videos — bottles popping open like champagne, booch spraying everywhere. It looks wild, right?

But here’s the truth: most new brewers don’t end up with explosions. Instead, their kombucha is flat. No fizz, no bubbles, just tangy tea that feels a little underwhelming.

So, why isn’t your kombucha carbonating — and more importantly, how can you fix it? Let’s break it down.

How Long Does It Take Kombucha to Carbonate?

After your first fermentation (F1), your kombucha has healthy acids and probiotics, but not much fizz yet. That comes during the second fermentation (F2), or the flavoring stage. when you bottle your booch with a little bit of sugar source (like fruit or juice) and let the yeast create carbon dioxide.

Typically, it takes 3–5 days for kombucha to carbonate in F2. The exact time depends on temperature, bottle seal, and sugar content.

Related: How Does Temperature Affect Kombucha?

Why Isn’t My Kombucha Fizzy? (Most Common Causes)

Here are the main reasons your kombucha may not be carbonating:

Not Enough Sugar for the Yeast
Yeast eat sugar and produce CO₂ (the bubbles!). Without a sugar source in F2, carbonation won’t happen.
Fix: Add fruit, juice, or purees when bottling. WARNING: I personally only use whole fruits and herbs in my kombucha. Juices and purees have sugar. Too much sugar equals exploding bottles and let's face it, you're sweet enough. 

Not enough yeast

As mentioned above, yeast consumes the sugar which results in carbonation. However if there isn't enough yeast in the bottles, then the result is flat kombucha.

Fix: Stir your flat, unflavored kombucha before you decant into the bottles that you use for flavoring. Why? This kicks up the yeast ensuring that every bottle has enough to consume the the sugar therefore producing the bubbles you desire.

Loose Bottle Seal
Carbonation needs pressure. If your bottles don’t seal tightly, CO₂ escapes instead of staying in the liquid.
Fix: Use swing-top bottles or tested brewing bottles (not recycled store kombucha bottles. Swing top bottles can loosen over time so be sure to check. 

Advance technique; The F2 vs. F3 Method: My Secret to Better Flavor and Fizz

Here’s a little secret from the 3rd Bird kitchen: I actually separate flavoring and carbonation into two distinct steps.

Second Fermentation (F2): Flavoring Stage
Instead of flavoring directly in your final bottles, I use wide-mouth mason jars with easy-grip lids. I drop fruit, herbs, or spices into disposable tea bags (so easy to clean!) and let them infuse for about 1 day. This step is all about building flavor without worrying about pressure.

Third Fermentation (F3): Carbonation Stage
After flavoring, I just remove the tea bag with the fruit and herbs I used for flavoring my homebrew and decant the kombucha into bottles with smaller openings (like old kombucha bottles or flip-top bottles). This is where carbonation really builds over 2–3 days.

Bonus: Breaking fermentation into 3 stages doesn’t increase the total brewing time. It just makes the process cleaner, safer, and more reliable.

Want to see the exact supplies I use for both stages? Check out my Kombucha Homebrewing Kit Shopping List.

Too Cold
Yeast does not like cold temperatures. Cooler temperatures cause yeat to get sluggishand slow down.  If your bottles sit below 70°F, carbonation may take forever — or not happen at all.
Fix: Store your bottles in a warm, consistent spot during F2.

Related: What Is the Best Temperature for Kombucha Fermentation?

Weak Starter Tea
Your starter tea is your liquid gold. It is what transforms sweet tea into your favorite probiotic tea beverage. If your starter is weak, then the whole fermentation process will be weak. To tell if your starter tea is strong enough, take a sip of it. If you make the same face that you do when biting into a lemon, it's good to go. 
Fix: If your starter isn't strong enough, leave it for a few days to ferment longer. More fermentaion time equals tarter kombucha.

Flat Kombucha Isn’t a Bad Thing

Flat booch might not be the outcome that you wanted,  sparkle you want, delicious and useful. You can:

• Add your favorite bubbly drink creating fun new cocktails/mocktails
• Use as salad dressing base
• Add to marinades for tang

So don’t pour it down the drain — your flat batch can still shine.

Why This Matters for New Brewers

A lot of beginners feel discouraged when their kombucha doesn’t fizz — they think they “messed it up.” In reality, flat kombucha is one of the easiest fixes once you know what’s happening.

That’s exactly why I created No Stress Kombucha: Step-by-Step Masterclass to Homebrew Success — to help you skip the stress and confidently brew booch that’s delicious, balanced, and (yes!) bubbly.

If carbonation is just one of the things stressing you out, this course will walk you through each step so you can avoid guesswork and finally enjoy homebrewing.