Beer Fermenters: How Do They Work?

In the following article, I am going to explain and try to answer as many questions as possible about what is usually considered the most important device in a brewery: the fermenter.

I will go over what fermentation actually is, what fermenters are and how they work, their different “features”, if you want to call them that, and the different types of fermenters that there are.

Without any further ado, let’s get started!

So how do fermenters work? A fermenter is a tank that is designed to carry out fermentation by storing the wort and the yeast until fermentation is complete. It must have valves and taps that allow the yeast to be purged, samples to be taken, and the CO2 produced inside it to escape.

Before actually getting into how a fermentor really works, I think it’s best to quickly go over what fermentation is:

First of all: What is fermentation?

If we’re talking about beer fermentation, then fermentation is a process by which living yeast cells convert the sugar present in the wort into alcohol and CO2.

This is the most important part of the brewing process since it’s where most problems, such as infections, can arise, which means that great care must be taken when cleaning & sanitizing all of the equipment, and the fermentation temperature must also be thoroughly controlled since it plays a vital role in how well the beer turns out.

What are fermenters and how do they work?

There are several types of fermenters ranging from simple plastic buckets to large stainless-steel tanks, but in general, a fermenter is a cylindrical container or tank, which, in most cases, at least when talking about higher-grade equipment, has a cone-shaped bottom. 

A fermenter is designed to contain the wort that was brewed beforehand and which is then “mixed” with the yeast to produce the fermentation. The more sophisticated our fermenter is, the more features it will provide to make the whole process easier and safer. 

Some of these features are:

  • Butterfly valves: these are valves specially designed to be easily cleaned and allow the passage of liquid in a safe way.
  • Manhole: In large fermenters, there are often Manholes that allow us to inspect the interior more easily.
  • Pressure Relief valve: This is a device located at the top of the tank which, in the event of an excessive increase in pressure inside the tank, allows us to release it.
  • Sample Valve: This is a small tap on the front of the fermenter that is used to pour beer directly into a glass or container.
  • Rotating Rack Arm: This is a tube that is inside the tank and that can be rotated to extract beer at different heights, usually found at the same height that the cone is at.
  • Carbonation stone: this is a submersible porous device that is designed to diffuse CO2 gas directly into the beer.
  • Venting Pipe: through a hole in the upper part of the fermenter, a pipe comes out that goes downwards and is used to release the gases produced during fermentation.

The importance of the Airlock

The airlock is a device created to allow the release of the gases produced by the yeast during fermentation without anything from the outside entering the container, which makes it favorable for brewing beer.

Its main advantage is its small size. 

Some of its disadvantages are:

  • They easily overflow at the initial stages of fermentation when it’s more vigorous.
  • In case of clogging, they can stop working, causing an excessive pressure build-up inside the fermenter (they may burst).

Different types of fermenters

In the world of craft beer, you can choose different types of fermenters of various shapes, sizes, materials, and costs, from plastic buckets to large stainless steel tanks. 

The types of fermenters you can find are:

Fermentation Bucket

Typical Bucket fermenter used for the Brewing Process.

These are the most used and economical fermenters that exist in the homebrew world. These containers are usually white and have a lid on top and a hole for the airlock. Some may even have a tap at the bottom to take samples or empty the fermenter more easily.

Carboy (Glass)

These are big glass bottles originally designed for transporting and storing liquids and are among the most popular fermenters because of their high quality, they are easy to clean, and they allow you to see what is happening during fermentation.

Carboy (Plastic)

These are just normal plastic carboys that have the same shape as the glass ones I just mentioned and are generally used for transporting and storing liquids, most commonly water (the big water jugs you can buy for your home).

Stainless Steel

Stainless Steel Fermenter.

The steel used for these kinds of fermenters is the so-called 304 food-grade stainless steel, and these fermenters can be cylindrical or conical.

Stainless steel fermenters, mainly because of their robustness as well as high price tag, tend to be used mostly at large-scale breweries and not so much by home brewing enthusiasts.

Conical Fermenter (Plastic and Steel)

Plastic Conical Fermenter.

These are, bar none, the best option when it comes to microbreweries since they have a large number of features that facilitate most of the processes that need to be carried out during and after fermentation (yeast harvesting, dry-hopping, additions of fruit and spices, etc.).

As for their physiognomy, they have a cylindrical top that ends in a conical base and they generally have valves and taps on the top, front and bottom.

They may also have doors at the front, called Manholes, which serve as a way to inspect the tank from the inside (this is mainly the case with big large-scale conical fermenters).

You can also read our guide on how to choose a fermenter here.

The most recommended one

Regardless of the cost, I definitely recommend the stainless steel conical fermenter, as it can brew any style of beer, does not deteriorate over time (as long as it’s taken care of properly), and allows you to clean it easily because you can use chemicals such as caustic soda, plus they have valves to which hoses can be attached, and they also withstand high levels of pressure.


Fermentation is the most important part of brewing beer, both at a home- and industrial level, and therefore, the fermenter is of vital importance if you want to achieve a good-quality product. 

During the fermentation stage is when most of the contaminations that generally absolutely ruin the way your beer turns out, occur. 

You should always use proper cleaning and sanitizing techniques in order to keep your beer batches from spoiling, and as I just mentioned, this is simpler with stainless steel fermenters.

However, you should mostly consider buying the one that your wallet allows and then move on from there.

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