The airlock, also called a bubbler, is an essential fermentation device that protects your cider from bugs, bacteria, oxygen and other undesirables during fermentation. It allows excess CO2, a byproduct of fermentation, to escape the fermenter while keeping a protective layer over the cider, beer, wine or anything else that you are fermenting.

This simple device is generally made from plastic or glass that is partially filled with water or other liquid. The airlock is then inserted into a rubber stopper that is sized to fit into the opening of the fermenting vessel creating an airtight seal.

A plastic three piece airlock fitted to a one gallon carboy full of fermenting cider

While some DIY or natural living blogs suggest improvising by using a cloth or a balloon, these will likely lead to contamination or oxidation. Cloth may keep the bugs out but bacteria, mold and undesirable yeast could go right through and spoil the batch.

Do yourself a favor and spend the $1 to buy a proper one, it will pay for itself by not ruining a $50 batch of cider.

Types of Airlocks for Fermentation:

There are three main types of airlock setups that are cheap and super simple to use.

S-Style Airlock:

The S-style is the simplest style of airlock that just works. Fill the s-shaped airlock tube with water up to the full line and secure it into the fermenter using a bung or gasket. It’s really that easy.

As the CO2 is forced into the airlock, the CO2 displaces the water in the bottom of the airlock. Once the bubble makes it past the U shape it moves to the bigger chamber. As it escapes the airlock, water fills its place before outside air can enter.

3 Piece Airlock:

The 3 piece airlock, as you have probably figured out, has three main pieces. The body, the float, and the lid. The 3 piece design works in a very similar way, the CO2 builds pressure under the float that is submerged in water. Once the pressure of CO2 overcomes the water, a bubble of CO2 is released.

This design is nice because it can be taken apart and easily cleaned where the S-style is very hard to clean internally.

Homemade Blowoff Tube:

A simple homemade airlock design is the blow-off tube. The blow-off tube is meant to allow krausen overflow to escape during very active ferments where a traditional airlock would be filled with foam and likely blown out of the fermenter. Messy.

A blow-off tube can be made from food safe plastic or metal tubing that is fitted to the opening of the fermenter with one end and the other is placed in a bucket of water. The CO2 will be pushed into the hose, through the water and bubbles out.

While a blow-off tube is typically a temporary solution, it can definitely be used as a homemade solution if a traditional bubbler style airlock is unavailable.

How to attach an airlock?

The easiest way to attach an airlock to a fermenter with a wide opening, such as a carboy, is to use a bung or rubber stopper. There are also handy carboy caps that can be fitted to the top of the carboy and be used to attach an airlock or a blowoff tube. If you use a fermenter such as the Ale Pale, there will be a premade hole in the lid with a rubber gasket that is designed to fit most airlocks.

What to fill an airlock with?

An airlock needs a liquid to complete the seal between the fermenting cider and the atmosphere. This is what it is sometimes called a bubbler, as the CO2 exists the airlock, it will make a bubbling noise.

While just about any food safe liquid could be used, it is important to use one is not conducive to growing mold or bacteria and won’t impart flavors in your cider.

Accidents happen and sometimes when pulling out an airlock, some of the solutions can be sucked back in. It’s hardly something to pitch your batch over, but filling your airlock with the right liquid will lessen the chances of contamination.

Fill the airlock with:

  • Water is convenient and works great
  • No Rinse Sanitizer left over from cleaning
  • Vodka will sanitize anything that comes in contact with it and will add ABV if an accident happens.
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