Tuesday, June 5, 2012

DIY Homemade Fermentation Chamber From Picnic Cooler

By: Orion Chandler

Completed Fermentation Chamber.

This tutorial will show you how to make a homebrew fermentation chamber yourself out of a picnic cooler and other common parts. The great thing about this is that it lets people who live in small places like apartments ferment in places like closets and storage spaces without the use of an expensive refrigerator or chest freezer.

A fermentation chamber is essential in controlling the temperature that your homebrewed beer, cider, fruit wine of wine ferment at. For those of us fond of brewing German wheat ales, a steady and low temperature is desirable in avoiding off-flavors like banana and clove that the yeast produce when fermenting too hot. A chamber like this will give just enough heat o ferment perfectly within +/- 1 degree. The scope of this design is really meant for cool weather use, as it has no way to cool your homebrew down, it will only heat it up and keep it at a temperature that is equal to or warmer than ambient temperatures outside of the picnic cooler. This chamber is sized for a 5 gallon glass carboy. Here is a list of what you need to build it:


1. 22' length X 12' width X 12' depth picnic cooler. This corresponds to a 9 gallon picnic cooler, or 36 quarts as they are often sold by.

2. Heating blanket.

3. Temperature controller. Mine is a Ranco ETC-111000-000 digital temperature controller.

4. 5 gallon glass carboy.

5. # 7 rubber stopper with hole same diameter as outer diameter of tubing.

6. 30'-36' length of vinyl tubing.

7. 16oz plastic soda bottle.

8. One clip to hold the tube to the plastic bottle. This clip can be found at any homebrew shop and is a tool to clip the tubing which then attaches to the side of your bottling bucket or fermentation chamber and is used to steady the tube while racking from one container to another.

9. Duct Tape (optional)


1. Place the heating pad inside and at the bottom of the chamber, now place the carboy on it inside. Set the heating blanket to medium. I am assuming you have racked your liquid into the carboy already.

2. Tie the temperature probe around the neck of your carboy and allow to hang about halfway down the side.

Carboy with temperature probe tied around neck.

Optionally, you may place the temperature probe between the carboy and some wadded up bubble wrap to act as an insulator and let you measure the temperature of the liquid inside of the carboy, instead of the ambient temperature in the chamber. This may be important if you are fermenting with a vigorous yeast strain that heats itself up in the initial stages of fermentation.

Place the probe in the center and tape to the carboy.

Here is a better picture of the bubble wrap used to insulate the temperature probe:

Two layers of small bubble wrap with duct tape around the edges.

3. Insert the rubber stopper and tubing into the carboy. Place the opposite end of the tubing into the plastic soda can filled half way with a sterilizer of your choice, my vote goes to Starsan Rinse Free Sterilizer. You may want to duct tape this plastic bottle in place so it doesn't fall out as the door to the cooler is opened. This style of airlock is used since a regular bubbling airlock won't fit. This type of airlock is common and is referred to as a blow-off hose.

Plastic bottle at bottom left with blow-off hose inserted.

4. Set your temperature controller and plug in the heating blanket to the controller and you are all set! This is the only way I ferment my ales in the winter and would highly recommend it to anyone with the parts available.

Leave a comment!

Feel free to email me with any questions or suggestions!


  1. since when is clove or banana an off flavor for German Wheats?


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