🛑 Airlocks and Bungs in Home Brewing
Airlocks and bungs are small pieces of kit, but they’re absolutely vital to successful home brewing. Without them, your carefully prepared wine, beer, or cider risks contamination and spoilage. While simple in design, these devices create a safe environment for fermentation to complete — and they’re worth every penny.
🔄 What Do Airlocks Do?
An airlock is a clever but simple device. It allows carbon dioxide gas to escape during fermentation while preventing airborne bacteria, moulds, or wild yeasts from entering your fermenter. Essentially, it’s a one-way valve for your brew: gases go out, nothing unwanted comes in. This makes them critical for both primary and secondary fermentation stages.
💧 What to Fill Airlocks With
Airlocks are usually only part-filled. Many beginners simply use plain water, and this works fine. However, a weak steriliser solution (such as a no-rinse sanitiser or even a sulphite solution) provides extra protection against contamination, especially if fermentation lasts several weeks. If the liquid evaporates, simply top it up again to maintain the seal.
🧩 Different Types of Airlocks
There are several designs of airlocks available:
- S-shaped (Twin-bubble) – The most common type, cheap and reliable. Gas bubbles through the liquid as fermentation progresses, making it easy to see activity.
- Three-piece (Cup-style) – A slightly bulkier version, easier to clean, and often favoured for larger batches.
- Specialty airlocks – Some modern fermenters come with built-in airlocks or waterless versions, but the principle remains the same.
No matter the type, they all work on the same principle: gas is released through a liquid barrier while contaminants are kept out.
🧱 The Role of Bungs
Bungs are the stoppers that hold the airlock securely in place. They are usually made from rubber or silicone and come in a range of sizes to fit fermenting buckets, demijohns, or larger carboys. A tight-fitting bung is crucial because if it’s too loose, oxygen and contaminants can slip in around the edges. Always match your bung to the neck size of your fermenter.
🎈 Low-Cost Alternatives
If you’re brewing on a tight budget, there is a DIY option: a balloon fitted over the neck of the demijohn with a tiny needle hole. As the gas builds up, it inflates the balloon and then gently releases pressure through the pinhole. While this works, it is no substitute for a proper bung and airlock. A good-quality set is inexpensive, durable, and far more reliable.
🧽 Cleaning and Maintenance
Airlocks and bungs should always be cleaned and sterilised before and after use. Residues of yeast or dried sugars can harbour bacteria and compromise future batches. Soak them in steriliser, rinse if required, and allow to dry before storage. Silicone bungs tend to last longer than rubber, which can perish or harden over time.
🛠 Common Problems and Solutions
- Liquid sucked back – If temperature changes rapidly or the fermenter is moved, liquid can be drawn back into the brew. Using a steriliser solution in the airlock instead of water makes this less risky.
- Leaks around the bung – Ensure the bung fits snugly. If in doubt, try a slightly larger size or switch to silicone.
- No bubbling visible – Sometimes fermentation is complete, or the seal is too loose. Check gravity readings with a hydrometer rather than relying only on bubbles.
🛒 Recommended Airlocks and Bungs
Airlocks and bungs are inexpensive but indispensable. For best results, keep a few spares on hand so you’re never caught out mid-brew. They’re often sold in multipacks, making it easy to build up a reliable collection.
👉 Browse a wide selection of airlocks and bungs on Amazon here: Shop Airlocks & Bungs on Amazon
🍷 Beginner Alcohol Brewing Equipment
This post is part of a comprehensive guide to home wine, cider, beer, and mead equipment. It covers one specific topic, but there are many other essential tools and additives you may need to create successful, clear, and tasty brews. For a full overview, visit our Wine & Brewing Equipment Page.
Here’s a quick list of all the posts in this series: