How To Perform A Swamp Cooler Homebrew Experiment

While many beers can brew happily at an ambient temperature, some prefer things a little bit cooler.

If you don’t want to invest in an expensive fermentation chamber, then you might be thinking about using a swamp cooler.

Swamp coolers rely on evaporation to bring down temperatures, and keep them low.

The simple set-up requires just a big bucket of water and a damp towel, so it’s easy to do at home. Just make sure to check the temperatures regularly, and adjust as needed.

Brewing at the wrong temperature can cause the yeast to misbehave, resulting in an undrinkable beer. Learn how to use a swamp cooler here. 

What Is A Swamp Cooler?

The swamp cooler is a type of fermentation chamber that uses a combination of frozen water and evaporation to keep your fermentor cool, and at a relatively consistent temperature.

Swamp coolers are very basic. They consist of a large bucket, filled with water and ice.

The fermentor is then placed in the bucket, and covered in a wet towel or t-shirt. As the water evaporates, it wicks across the towel, cooling the fermentor below.

Swamp coolers are often used by brewers who are struggling to maintain a low temperature, and don’t want to invest in an expensive set-up. 

How Do You Make A Swamp Cooler?

Swamp coolers are very easy to make, and require just a few simple pieces of equipment.

Essentially, a swamp cooler consists of a large bucket filled with water and ice, and a damp towel. The fermentor or carboy is then placed in the middle of this.

So, let’s look at how to make a swamp cooler in a little more detail.

What Do You Need To Make A Swamp Cooler?

Swamp coolers are low-cost alternatives to fermentation chambers, and are popular with home brewers trying to keep to a tight budget. To build a swamp cooler, you need:

  • A plastic tub. The plastic tub is the main part of the swamp cooler. It needs to be big enough to hold your carboy, and still have room for water and ice packs. Trash cans are popular choices, because they’re cheap. I recommend buying a model with handles. It’ll make transporting the swamp cooler so much easier, and you’ll be grateful when it’s time to empty out the water.
  • A dark towel or t-shirt. A damp towel or t-shirt is used to wick away moisture, keeping the fermentor cool. It has to be big enough to cover the top of your fermentor and dangle into the water. Dark colors are preferable.
  • Ice packs, frozen bottles, bags filled with ice. Ice packs, frozen bottles of water, and bags filled with ice can all be used to lower the temperature of the swamp cooler. If you want to use ice chips, place them in a ziplock bag before adding to your cooler. When they melt, the bags can then be removed easily, and refrozen. If you put ice directly into the water bath, you’ll find it tricky to replace as the temperature rises.
  • Water. The swamp cooler needs to be filled with water, which will slowly evaporate, maintaining the temperature across the carboy.
  • A thermometer. The purpose of the swamp cooler is to keep your fermentor at a reasonably even temperature. A thermometer should be used to ensure the temperature is within the necessary parameters. 
  • Optional: a fan. Some home brewers choose to add a fan to their swamp cooler. This blows cold air onto the cooler, keeping the temperature low, and aiding the evaporation. You may or may not find the fan to be necessary.

Now, you can get on with making your swamp cooler.

How To Use A Swamp Cooler


Swamp coolers can be used to create and maintain a low temperature for fermenting certain styles of beer. 

  1. Place your fermentor/carboy into a large tub or trash can. 
  2. Fill the tub with water, up to the level of, or just above, the beer level in the carboy.
  3. Add your ice. Ice packs and frozen water bottles are a quick way to add ice, and they’re easy to clear up. You can also use ziplock bags filled with ice chips.
  4. Check the temperature of the water. If necessary, add or remove ice.
  5. Soak the t-shirt or towel in cold water, and wrap over the top of the fermentor. The fabric should be clinging to the fermentor, and the edges should be in the water.
  6. Optional: direct a fan towards the swamp cooler. A fan can help to keep the temperatures low, but you may not find it necessary.
  7. Regularly check the temperature, and change the ice as needed. Depending on the ambient temperature, the ice will need to be replaced more or less frequently. Begin by checking every three hours. If the temperature is good, you can wait longer between checks.
  8. Keep checking the temperature and changing the water until your beer has finished fermenting. 

And, you’re done! The hardest part of using a swamp cooler is the temperature checking. If you find the ice is melting too quickly, consider adding a fan. 

Are Swamp Coolers A Good Method For Cooling Fermenting Beer?

Swamp coolers can be an excellent method for maintaining a low temperature without needing to invest in a complicated set-up.

Most of us have a trash can large enough for a carboy, a dark towel, and a few old water bottles. 

However, there are some issues with the swamp cooler. The big one is maintaining temperature.

Often, it’s better to have your beer ferment at a slightly higher temperature, rather than expose it to constant fluctuations.

Depending on the ambient temperature, the swamp cooler might warm too quickly to do any good. 

But for most of us, the temperature in the swamp cooler will stay fairly consistent, even when left overnight. 

Final Thoughts

Swamp coolers might not be the most sophisticated method for keeping fermentors cool, but they do get the job done.

And if you aren’t quite ready to invest in an expensive fermentation chamber, then you should definitely give the swamp cooler a try. 

If you enjoyed this article, you might enjoy our post on ‘How To Ship Beer – The Ins And Outs‘.

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