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Swamp Cooler MAGIC!

After brewing up 12 gallons of American Wheat base beer last Friday night, I transferred it into three different fermentors and added my yeast.  Since I have been without a brewing fridge now for several months I was contemplating how I would keep these beers reasonable cool while they fermented.  I have used the “swamp cooler” method in the past but I was skeptical with the hot days we have been having and the fact that I was going to let the beers ferment in my non-insulated garage.

Pleasantly surprised, I checked the temp of my swamp coolers last night and they were at 65F!!!  I estimate that the beer should be holding at 70-72F.  Still a little warmer than I normally ferment at, but its definitely not too hot.

The beers are bubbling away nicely.  So all I have left to do now is rotate in and out the occasional frozen water bottle every 12 hours to be sure the temp doesn’t get away from me and I think these beers should ferment out just fine.

I’ll try and snap a couple pics tonight and update the post, but here is the basic premise of the swamp cooler:
I placed my bucket (or glass) fermenter into a cooler large enough to fit the bucket.  I then fill the cooler with normal tap water.  My tap water was about 65F to start with.  Next, I draped an old T-shirt over the fermenter and let the sides of it hang into the water.  Lastly, I added a floating thermometer to each water reservoir and I jammed in some “Blue Ice” cooler packs and or frozen water bottles.
The wet cotton T-shirt helps to pull heat away from the fermenter, much like sweating does on a person’s skin.  I like to rotate in the frozen bottles to help keep the water in the cooler from becoming to warm.  If you want your cooler to operate colder, you need to rotate the frozen bottles more frequently.  You can also increase the wicking rate by using a fan blowing across the wet T-shirts.  Currently, by changing the frozen water bottles every twelve hours I seem to maintain my 65F temp pretty well.
As fermentation slows, the beer won’t be generating its own heat as much, and I will be able to get the beer to cool off to 65F.
You can use any normal bin or tub rather than a cooler to hold the water.  But I like the cooler because it helps insulate the water a bit from the surrounding rising temp of the garage and the garage floor.

So don’t stop brewing in the summer.  Give the swamp cooler a try.  If I can maintain about 65F in a hot garage, a cool basement or closet should work even better.  Good luck.

Edit 7/2/08

Here are the pics of the swamp coolers in action.  I also took a picture of the “”blue ice” pack so you know what I am talking about.  After checking the temp last night I was still at about 65F.  I rotated in some more packs last night, then again this morning.  I double up on the packs in the morning because I expect the days to be warmer than the evenings.

Cooler1   Cooler2  Blue Ice Pack


Mt. Hood Hops


Summertime Update


  1. Aaron

    How hot is it in your garage? I’m curious just how much lower than ambient it’s getting.

  2. Can’t wait to see the photos of this set up. How low do you think you could get the temperature?

  3. Mike

    Great question about being below ambient. My garage was pushing 80F-85F yesterday. So I am about 15F below the ambient.
    I had glass carboy that was full of water sitting in the back corner when I started. The strip on the side was about 72F. But that was after several cooler rainy days. Saturday was a brisk 62F here. The carboy was also sitting on the concrete slab so I am sure that acts as a pretty good heat sink. I think that I may need to start rotating more ice bottles in an out as its starting to get warmer out. We’ll see what the temp of the cooler is when I get home today.

    Now I’ll definately get those pics up later tonight. I think you can get pretty cold but it requires rotating more and more ice/frozen matter through the system. If you were to use a ice and water combo I am sure you could get it close to 40F. But you’d really be winding through the ice, and you’d need to drain off water quite frequently. You are only limited to how cold you can get (AND MAINTAIN) the ice water. Maybe even adding some salt to the water would help get the temp even lower.
    What do you think?

  4. I think I have a concept for lagering in my basement in the winter.

  5. Brennen

    I did this with an old metal veggie crisper tray from some old fridge I had. It was about 7″ deep and I guess somewhere around 18-20″ square. I took a wet towell and wrapped it around my fermentation bucket, threw a bit of ice in the tray. Kept it in my closet and it worked great. Kept a good 67-75* had to stay on it tho if I didn’t pay attention to it daily I would get too warm. Ambient temp??? 75-85* in closet. Gonna build a cooler box out of used pallets. Line it w/ insulation.. See what it does.

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