The most popular airlock. Protects against flies, oxidation and contamination. Suitable for containers in the range of 1-50 l. Fits a 9 mm hole.
What does an airlock do?
Filling the airlock with a little water makes it act as a siphon; the water closes the beer or wine off from the outside air; hence preventing outside bacteria from entering. However it allows the carbon dioxide formed during fermentation to escape through the airlock because of the excess pressure.
Twin-bubble airlocks are the cheapest, but these are harder to clean than the cylindrical models. With volumes of 50 l or more, the use of cylindrical airlocks is essential for the increased flow of carbon dioxide to be processed. The water in the airlock evaporates; regularly checking and refilling is necessary. The airlock can also be filled with a disinfecting solution instead of ordinary water.