Why Is My Airlock Not Bubbling? (And Is Fermentation Still Working?)

One of the most common concerns for new winemakers is checking on a batch and noticing that the airlock has stopped bubbling. It can feel like something has gone wrong — but in many cases, everything is perfectly fine.

Airlock activity is helpful, but it is not a reliable way to measure fermentation. This guide explains what’s really happening, when you should be concerned, and how to check your wine properly.

If you need tools to monitor fermentation accurately, browse our winemaking supplies.

Does No Bubbling Mean Fermentation Stopped?

No — not necessarily.

The airlock only shows that carbon dioxide is escaping. If it stops bubbling, it could mean:

• Fermentation is slowing down naturally
• The fermenter is not perfectly sealed
• Temperature has changed
• Fermentation is already complete

Many beginners assume that bubbling equals fermentation and no bubbling means failure — but that’s not always true.

Common Reasons Your Airlock Isn’t Bubbling

1. Fermentation Is Slowing Down

As yeast consumes sugar, fermentation naturally slows. Early stages are very active, but later stages can become much quieter.

This is especially common after transferring wine into a carboy, where fermentation becomes more controlled and less vigorous.

2. Your Lid Isn’t Airtight

If you're fermenting in a bucket, small gaps in the lid can let gas escape without passing through the airlock.

This means fermentation may still be active — you just won’t see bubbles.

3. Temperature Dropped

Yeast activity is highly dependent on temperature. If your room cools down, fermentation can slow significantly or appear to stop.

A small drop in temperature can reduce visible airlock activity without stopping fermentation completely.

4. Fermentation Is Already Finished

In many cases, the simplest explanation is the correct one: fermentation is done.

Once most of the sugar has been converted to alcohol, carbon dioxide production stops — so the airlock becomes quiet.

How to Actually Check If Fermentation Is Still Working

The only reliable way to check fermentation is by measuring gravity with a hydrometer.

Using a hydrometer and a testing jar, you can track whether sugar is still being converted.

• If readings are still dropping → fermentation is active
• If readings stay the same for several days → fermentation may be complete

Visual signs like bubbles or foam can be misleading — gravity readings tell the real story.

When You Should Be Concerned

You should take a closer look if:

• The airlock stopped very early in fermentation
• The wine still tastes very sweet
• Hydrometer readings are not changing

In those cases, fermentation may have actually stopped prematurely. If that happens, you may be dealing with a more serious issue.

👉 Read this next: Stuck Fermentation: Why Your Wine Stopped Fermenting and How to Fix It

Quick Tip: Don’t Rely on the Airlock Alone

It’s easy to focus on bubbling because it’s visible — but experienced winemakers rely on measurements, not guesswork.

Even a completely still airlock can be paired with active fermentation inside the vessel.

That’s why tools like a hydrometer are considered essential for consistent results.

Final Thoughts

A quiet airlock doesn’t automatically mean something is wrong. In many cases, it simply means your wine is progressing normally.

The key is to verify what’s happening using proper tools instead of relying on visual cues alone.

With a little experience, you’ll learn when to relax — and when to take action.