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Double-Pump Temperature Control

I want to get my fermentation temperatures down – or at least stable.

Currently, I just stick the fermenters in a spare bathtub filled partway with water, throw a shirt over it, and point a fan at it. Evaporation cools it down a bit, and the large body of water in the bathtub ought to serve as a pretty good buffer against temperature swings.

However, what I was thinking of doing is taking my MLT (a 10 gallon rubbermaid circular cooler), and filling it with ice-water. Then take one of those rope-handled tubs, also filled with water. Then use a temperature controller to flip on two $10 pond pumps, to push water back and forth between the containers.

This would allow me to keep the water that the fermenter sits in at the exact temperature that I want, without relying on a fan or traditional swamp cooler. It should also only cost about $30, excluding the cost of the temperature controller – I figure that I’ll eventually need the temperature controller anyway if I move to any kind of cooling (and I also want to play around with it and my kegerator). A pump would also be useful to pump ice-water through my immersion chiller to get the final few degrees down (tap water is about 75°).

Any fatal flaws in this? The bucket holding the carboy wouldn’t really be insulated, but I can throw an extra blanket around it to hold some of the temperature. I’d also have to worry about condensation, but I’m already putting everything in the tub.

Updated: I just realized I don’t have to use the MLT, I can get away with a cheap styrofoam container which means I can punch holes in the lid to the exact size of my water lines. Don’t have to destroy the MLT lid, it’s much more reasonably sized, and I can actually mash while using the chiller.

Moderators: It appears that the edit button is MIA

Before going the pump route, try adding some ice periodically to a generous water bath containing the fermentors and monitor the water bath temps. I sometimes use a water bath set-up if needed; I swap out frozen plastic containers twice a day to keep temperatures down. Once you figure out how much ice you need how often, its a pretty effective temp control method without pumping water around.

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