What Is A Thumper Keg and How Does It Work?

If you are interested in increasing the potency of your spirits or making a traditional backwoods moonshine, then you should grab a thumper keg for your still. It is a clever innovation which will increase the potency and purity of your distilled spirits.

In this guide, I’ll share everything you need to know about thumper kegs, including how they work, what they can do, and how to infuse flavor using one. I’ll also list a few of the best thumper kegs on the market. Let’s jump straight in. 

Key Takeaways

  • Thumper Keg: A copper, steel, or wooden vessel which is placed between the still pot and condenser.
  • What Size Thumper Keg to Use? A thumper keg should be 25% to 40% the size of your main boiler.
  • What Does a Thumper Keg Do? The main purpose of a thumper keg is to speed up the distillation process.

Related: Moonshining in Appalachia in 1900s

What Is A Thumper Keg?

A picture of moonshine on a wooden barrel.

The thumper Keg is a small copper, steel, or wooden vessel which is placed between the stillpot and condenser. It receives low wine from the stillpot and heats it again, sending highly purified alcohol vapors to the condenser. This creates a high-proof spirit without the need for double distillation (more on how a keg thumper works, below).

Also known as a Thump Barrel, Thump Chest, or Doubler, the thumper keg was very popular amongst Prohibition-era distillers and moonshiners in the Appalachians. However, it is thought that the thumper keg was invented in Europe many years earlier and came to America with the first settlers. 

It is called a Thumper Keg because of the thumping sound that the vapor and condensed low wine make when the still is in operation. Contrary to popular belief, the thumping sound is not caused by mash falling into the container.

Moonshiners interested in making potent spirits would sometimes place additional alcohol into the thumper, which would be distilled again to create a very powerful spirit.

Related: How to Proof Moonshine

How Does A Thumper Keg Work?

A normal still heats the wash (fermented solution) to a high temperature in order to release alcohol vapors which are captured by a condenser. The collected vapors yield a solution called the low wines, which are typically 25 to 35% alcohol by volume (ABV).

The low wines must be distilled again to create a distillate with a higher ABV. Most distilleries will use a beer stripper (a very basic still) to turn the wash into low wines, then a separate spirit still which turns the low wines into a high-proof spirit. Some distilleries will distill their spirits a third time to create a very strong spirit with a pure flavor. 

While the process of multiple distillation is a tried-and-true technique, performing two or three distillations can be time consuming and costly.

A thumper keg is a metal or wooden vessel which sits between stillpot and condenser. It is designed to help the distiller avoid the necessity of repeat distillations.

At the start of the distillation, the thumper keg is filled with a small amount of spirit tails from a previous batch (ideal), some wash from the current batch (good), or water (better than nothing).  Back in the day moonshiners would add a small amount of moonshine to the thumper keg, although this may give you a distilled spirit that is a bit too strong for your liking. 

As the wash boils in the potstill, heated vapors are drawn into the thumper keg via a swan neck. This swan neck sends the heated vapors directly into the solution contained within the thumper keg. 

As the vapor bubbles up through the liquid in the thumper, it is cooled into liquid form, adding more low wines to the thumper keg’s contents. A thumping sound is generated as the vapors exit the swan neck and condenses in the thumper keg.

The heat of the released vapors cause the solution in the thumper to reach the boiling point of alcohol once more. This causes more alcohol vapors to be generated, which are captured by the condenser, distilling the low wines a second time and creating a high-proof spirit. It is a very time and energy-efficient way to double distill a spirit.

Related: Facts About Moonshine

How To Infuse Flavor Into Moonshine with a Thumper Keg

Distillers usually add spirit tails, low wines, water, or whiskey to their thumper keg to cool the alcohol vapors coming from the potstill. However, you can include other fruits, herbs, or spices to add different flavor combinations to your spirits.

The best way to add these flavors is a heavily debated topic. However, some options to experiment with include:

  • Adding fruit infused spirits to the thumper keg
    Place your chosen fruits, herbs, and spices into a large container of low wines or head/tail spirits and let it sit for a week or two. The flavor of your ingredients will gradually infuse the solution. Add this solution to the bottom of the thumper keg to impart the flavors it contains. 
  • Adding juice or oils directly to the thumper keg
    Ingredients like apple juice, peach juice, blackberry juice, lemon juice, pineapple juice, orange juice, and coconut oil can be added directly to the thumper keg to impart flavor.
  • Adding raw ingredients directly into the thumper keg
    Some distillers will add fruit peel, herbs, spices, and mashed fruit directly to the thumper keg. Just be aware that mashed fruit will need to be added in large quantities and may be messy to clean up. If using this technique to add fruit, make sure your produce is very ripe.

When using the thumper keg to add flavors, it’s best to add your ingredients after the spirit’s heads have been extracted. This will ensure the flavors are impacting the part of the distillation which you actually drink.

Related: Beginner Moonshine Stills

How Big Should a Thumper Keg Be? 

A thumper keg should be 25% to 40% the size of your main boiler. If you plan to prime your thumper keg with a sizable charge (botanicals, low wines, wash, water, etc), use a thumper keg that is at least 50% the size of your main boiler. 

What Size Thumper Kegs Are There?

If you are looking to buy a thumper keg, there are several options available. One option is to buy a complete thumper keg that is made from copper, stainless steel or timber. There are also complete kits which include main boilers, a thumper, and a condenser. 

If you are looking for a cheaper option, you can buy a mason jar jumper kit. This contains a copper tube and seal that can be screwed onto any mason jar. Here are a few of the best options:

DIY 2 Gal 10 Liters Home Distiller Copper Thumper Keg

DIY 2 Gal 10 Liters Copper Alcohol Moonshine Stills Ethanol Still Spirits Boiler Water Distiller
  • Moonshine Stills - complete distillation equipment,suitable for beginners or expert distiller,easy to handle and installation.
  • Material and Construction - safe & non-toxic red copper and stainless steel material,There is NOT ANY lead in all the parts, all the parts are made of food-grade materials,The fermenter is specially thickened.(Dimensions:capacity: 2 Gallons / 10L, Height: 9.8inch, Diameter: 9.8inch.)
  • Build-in Thermometer - Metal Thermometers show as: Celsius & Fahrenheit, So Operator can Inspect the Temperature easily when Running the Distiller,Free Stainless Steam Plate and Gauze Bag, to prevent Burn Out, and has much better on distillation. Free Temperature Sticker on the Fermenter, can inspect the Temperature when use the big pot as a Fermenter Pot.

This high-quality stainless steel thumper is a wonderful choice for the home distiller. It uses 100% lead-free, food-grade materials that are fully non-toxic and purpose built for distillation. This thumper keg kit is available in 4 different sizes, (2 gallon/10 liters, 3 gallon/12 liters, 5 gallons/20 liters, and 8 gallons/30 liters). 

Stampede Stills 2 Gallon Copper Moonshine Still Thumper Keg (Doubler)

Stampede Stills 2 Gallon Copper Moonshine Still Thumper Keg (Doubler)
  • Made from 20 ounce copper sheet.
  • Hold 2 Gallons of liquid.
  • Lead Free 1/2" ball valve drain

A 100% copper thumper keg made from a 20 ounce copper sheet. It holds 2 gallons of liquid and comes with a ½” ball valve drain and 1/2” copper pipe handoffs. All materials are lead-free, including the silver based solder.

Stampede Stills Copper Widemouth Mason Jar Thumper Kit

Stampede Stills Copper Half Gallon Widemouth Mason Jar Thumper Kit
  • Made from 20 ounce copper sheet, silver based lead-free solder, gasket, and is 1/2" copper pipe. The inlet pipe has an elbow to prevent hot spots on the bottom glass.
  • 1/2" copper pipe stubbed out for easy plumbing to your existing still. Additional pipe/coupling/unions to connect to your setup are NOT included as everyone's still is slightly different.
  • Works on 1/2 gallon canning Mason jars with standard wide mouth lids.

This is a handcrafted copper tube and seal which can be used to convert any wide mouth mason jar into a thumper keg. The beauty of this kit is that it is very affordable, so you can easily create a multi-jar setup, where you triple or quadruple distill your spirit. The pipes are stubbed out, so you will need to connect your pipes yourself.

YUEWO 3 Pots DIY 2 Gal/10 Liters Moonshine Still

YUEWO 3 Pots DIY 2Gal/10Litres Moonshine Still Copper Water Alcohol Distiller Home Brew Wine Making Kits with Thumper Keg for DIY Brandy Whisky Wine Essential Oils
  • Moonshine Stills - complete distillation equipment,suitable for beginners or expert distiller,easy to handle and installation.3 Pots Distiller,Innovative the Steam flow into the side of Fruit/Spice Pot, flow out from the top,So operator can brew his own taste easily!
  • Material and Construction - safe & non-toxic red copper and stainless steel material,There is NOT ANY lead in all the parts,Stainless / Copper Coil cooling Tube , all the parts are made of food-grade materials,The fermenter is specially thickened.(Dimensions:capacity: 5 Gallons / 20L, Height: 9.8inch, Diameter: 9.8inch.)
  • Build-in Thermometer - Metal Thermometers show as: Celsius & Fahrenheit, So Operator can Inspect the Temperature easily when Running the Distiller,Free Stainless Steam Plate and Gauze Bag, to prevent Burn Out, and has much better on distillation. Free Temperature Sticker on the Fermenter, can inspect the Temperature when use the big pot as a Fermenter Pot.

This is a complete moonshine still kit which i ideal for making any kind of spirit from scratch. It comes with a large 10 liter boiler, thumper, condenser, and all connecting pipes. Made from non-toxic red copper and stainless steel components it is 100% safe and non-toxic. Comes with built in thermometers which makes tracking the progress of your distillation simple.

What Is The Purpose Of A Thumper Keg?

The main purpose of a thumper keg is to speed up the distillation process. It lets you distill a high-proof spirit without running it through the still multiple times.

The other purpose of using a thumper keg is to add botanicals to your spirits. It becomes simple to introduce fruits, spices, and herbs, creating delicious new flavors and aromas in your spirits. 

Related: List of Moonshine Distilleries

How To Clean A Thumper Keg?

The simplest way to clean a thumper keg is with a vinegar run. Fill your boiler to 20% capacity with a mixture made from 50% hot water (distilled is best) and 50% vinegar.

Run it through the still as if you were making a spirit. Let the still reach 170 degrees F and run it for 5 minutes. Turn off your heat source, let it cool, and empty the vinegar solution. This will only need to be done on a new thumper keg, then two or three times a year.

Related: How to Clean a Keg