How Does a Thump Keg Work?

How Does a Thump Keg Work?

Do you want to make quality moonshine with less effort? Let us introduce you to your next best friend-the thump keg! 


Making your own moonshine can be quite a head-scratcher if you are new to this hobby.  When you make your own alcohol you need to understand different processes such as fermentation and distillation.

You will also need to learn all about equipment like the still, thump keg and warm box before you can get to brewing.

Most new whiskey makers are all too familiar with the still because this is one of the most critical parts of the whiskey-making process.  But one of the components you might not be as familiar with is the thump keg.


The thump keg is called a thump keg because pieces of corn sometimes rise with the vaporized alcohol and will then make thump noises when it falls into this heated barrel. 


In this article, we are going to explain exactly what a thump keg is and we are sharing a few great tips on the best ways to use your thump keg to modify the taste and potency of your whiskey. 


What is a thump keg?

The thump keg has been part of the whiskey-making process for a very long time.  The main purpose of a thump keg is to distill your output of a pot still a second time without having to run the product through the still a second time or to alter the taste and potency of your moonshine.

You can produce a low-quality whiskey with just a pot and no thump keg.  These spirits usually yield around 40 – 50% alcohol after a single run.

Those who want to create a high proof whiskey will then do a second run using the same product to increase the taste and quality of the still.

With a thump keg, you can create much higher quality still without having to go through the entire process all over again.  The thump keg also eases the process because the still and thump keg setup will do all the work for you. 



The Design of a Thump Keg

Thump kegs do come in a variety of designs.  Many whiskey makers prefer wooden barrel thump kegs because wood doesn’t lose as much heat as quickly as metal thump kegs do.  The temperature in the thump keg is just as important as in the main still.

In the still, the temperature rises and causes vaporization.  Vapors rise through a copper tube into the thump keg where the vapors are reconverted into a liquid state. 

The warmth of the thump keg causes the liquid to once again vaporize and escape through another copper tube that leads to the condenser.  In the condenser, the vapor is cooled down and transforms back into a liquid state. 


A thump keg can be replaced with a reflux column still

thump keg


The thump keg can also be replaced by a reflux column still.  These stills are filled with various materials such as copper mesh.

When the vapor passes through the column still, the liquid is processed and reacts with the copper to rid sulfur from the product.  Reflux column stills can produce a spirit with a 95% alcohol level. 

Many do however prefer a thump keg above the reflux column still because thump kegs are easier to find or build and a lot cheaper to invest in.

Moonshiners also prefer to use a thump keg because the result tastes more like a quality whiskey where the product of a column still is often associated with the taste of vodka.

Some whiskey producers also prefer to leave out the thump keg and are happy to rerun the entire proses using a sour mash to maintain a specific alcohol percentage and a specific taste for their whiskey. 



whiskey still for moonshine


Thump kegs can be used to impact whiskey flavor

Another reason so many moonshine makers love to use a thump keg is because they can use the thump keg to modify the taste of the whiskey.  By adding certain ingredients such as fruits, herbs or spices, the taste and essence of the alcohol can be changed and more interesting spirits can be created.


How does a thump keg work?

If you are using a thump keg for the first time then always remember to give it a good clean before using it so you can eliminate the chances of contaminating your still.

Once your thump keg is clean you can start putting together your setup.  Here is a quick look at what you need;


  • Stillpot
  • Whiskey ingredients such as cornmeal, sugar, yeast, and water
  • Thump keg
  • Copper tubes
  • Condenser


Fully assemble your whiskey making kit before you start mixing ingredients.  Many moonshiners build their own whiskey making kits complete with thump keg completely from scratch. 

You can, however, save yourself a lot of time by simply buying the best whiskey making kit that is already fully constructed.

Once your setup is complete, you can start using your thump keg.  Here are the steps on how to work this setup;


Make your mash

Before the product can reach the thump keg, a mash needs to be made in the still pot.  In this process, cornmeal will be soaked in hot water inside the still.

Sugar is also sometimes added instead of grain.  Yeast is then added to the mixture which starts the fermentation process.

This mixture takes a few days to fully transform into what is called mash. 

The heat of about 172 degrees is then applied to the still so the alcohol can start to evaporate.  This alcohol steam will then rise through the cap arm into copper pipes.  In these copper pipes, the vapor is transferred into the thump keg.


Can you Add Fruit to a Thump Keg?

Some moonshiners choose to add specific ingredients such as fruits or spices to the thump keg.  When the liquid mixes with these ingredients, some of the fragrance is absorbed into the liquid which alters the taste and aroma of the whiskey.

Can you Increase the Potency of your Still with the Thump Keg?

Moonshiners that want to create extra potent alcoholic beverages can choose to “charge” the thump keg by adding undistilled mash or alcohol to the keg.  The steam that passes through the liquid will pick up some of the alcohol vapor before rising back up into the condenser.

The still in the heated thump keg will now begin to re-evaporate.  This process also filters out all mash pieces that drifted along into the thump keg.  The alcohol will now rise through a second copper tube where the vapors are cooled down in the condenser.


Condensate your Still

When the vapor escapes the thump keg, it rises into the condenser.  The condenser is also called the worm because it consists of a length of coiled copper pipe inside a worm box that is filled with cold water.

Many worm boxes are fueled by constantly circulated cold water so the condensation process will remain constant. 

When the vapor enters the worm, it is cooled down by surrounding cold water and the condensation process is instantly activated.  The steam is transformed into liquid alcohol and exits the tap or hose or spout into a bucket. 

Many moonshiners will also filter the moonshine one more time before bottling and selling their products.


Does a Thumper Need to be Heated?

Many moonshiners do prefer to heat the thumper.  The alcohol does need to stay in vapor form to be able to rise into the condenser.

Wood barrels are often preferred as thump kegs because of wood's natural isolative abilities.  Condensation in the thump keg is minimized and less artificial heat is required to vaporize the alcohol.



As you can see, using a thump keg doesn’t increase your workload.  If the thump keg is set up correctly in the whiskey-making kit, the still will automatically flow through the thump keg.

You can keep this process simply by allowing the vapor to simply pass through the thump keg without adding additional ingredients.

Your still’s alcohol level will still be increased dramatically but the taste can be blank.

If you want to increase the taste of your still then you can also choose to add fruits or spices to your thump keg. 

As the vapor passes through these products, the flavor will be absorbed and the taste of the whiskey will be altered for a more unique flavor.

It is best for beginner whiskey makers to focus on producing a low alcohol level still of around 70 – 80% until they become more experienced.

When you become more experienced and feel more comfortable with the process, you can choose to increase the potency of your moonshine by adding mash or alcohol to your still which will increase the alcohol level even more.

Thump kegs are quite simple to use and can be a huge help if you want to create a high-quality moonshine with a unique taste. 

These devices also reduce the workload and duration of whiskey-making dramatically compared to rerunning the still entirely through the pot still every time. 

 Many whiskey makers swear by this traditional whiskey making device but there are also modern moonshine brewers who love modern methods like the reflux column still.  But all in all, the thump keg is much more affordable to build and use than modern whiskey making parts.