Refrigerated Fermentation Water Bath

I have an office water cooler that I was given, but really didn’t have a need for. Ever since I acquired it, I’ve wondered what I should do with it.

Over at, there’s plenty of people making fermentation chambers using dorm fridges or altered window AC units. I started thinking that all this water cooler was is just a simple fridge of sorts. I didn’t realize how simple it was until I actually started taking it apart. It consists of a simple copper tube that is coiled around a plastic water tank which is gravity fed out to the spigots when someone wants a drink of cold water.

My idea was to immerse the cooling coil into a container like a bucket to cool the water or Propylene Glycol if I want to spend the money to do that and pump it through copper tubing wrapped around my carboys. That idea quickly went away when I realized the price of copper tubing. I decided the best way to conduct heat away from my carboys and to promote even cooling was going to be a water bath.

After talking with an AC guy to find out if there would be any issues with immersing the cooling coil in water (he said there weren’t any) I decided to move forward with the project.

I finished taking off the outside cabinet and started working on the wiring. This unit has a water heater built in, but being in Florida, I’m really not likely to need it so I disconnected it. I rewired the on/off switch that used to control the heater and put it inline with the cooler compressor.  I now had a way to turn it on and off when I needed.

I purchased a 50 gallon tub to use for the water bath. I keep my glass carboys in milk crates so I can move them around safely and I can fit two of them inside the tub with crates. If I go crate-less, I can fit three carboys inside but moving full carboys around without my milk crates makes me nervous! I placed a $10 Harbor Freight water pump inside the tub to circulate the water around. I carefully bent the copper cooling coil down into the water so it would be below the water line.