A Better Way to Chill Wort
By Calvin Perilloux
Wort chilling is a task that every serious homebrewer has to deal with, and depending on the beer and time of year, it can sometimes be one of the most challenging. Yet, if you can’t get the wort chilled to the right temperature, there’s a huge chance your beer won’t turn out as you hoped or expected.
We could write a nice, long paper on the methods and science of chilling wort, but to make it simple: (1) We need to get wort from 212° F to 70° F or lower, and (2) while we’re doing that, the temperature difference between the wort and the cooling water narrows, and so the rate of heat extraction drops dramatically.
You no doubt see this yourself if you use an immersion chiller, which chills wort quickly from 212° F down to perhaps 150° F or even 120° F, and then the rate of temperature change slows to an eventual crawl – as your water meter spins! So initially, temperature drops quickly, but then what? Use a hundred gallons of tap water to chill five gallons of wort? Or spend the money and for the next batch switch to a more efficient counter-flow or plate chiller?
The gist of it is this: Immersion chilling uses a lot of water, and if you want to get close to the temperature of the cooling water, it will use incredible amounts of water. When wort is 210° F and tap water is 65° F, you have a 145° F difference, and the cooling proceeds quickly. Once the wort gets down to 80° F, which is still too warm to pitch most yeast strains, there’s only a 15° F difference, and it takes your tap water (very roughly) almost ten times the water flow to keep cooling at that same rate.
Enter the well-known ice bath pre-chiller with a second coil. This can help, but you need to reduce flow to a frustratingly slow rate for the chilled water to really be cold. Worse, the water you use still goes down the drain. I used the pre-chiller method for chilling lager wort in late winter when I had a mountain of snow piled on the north side of the house – free chiller ice. It still took a lot longer than I expected.
There’s a far better alternative that uses little ice and saves a lot of water. I was helping one of the FOAM club guys with a problematic pre-chiller and hit on this method, then found various others on the internet also using it: Skip the pre-chiller hardware and simply recirculate the ice water itself through the wort chiller. The equipment for this chilling method is minimal. If you’ve already got an immersion wort chiller coil, all you need is some cheap tubing, a big bucket, and a fairly inexpensive submersible fountain pump. And a GFCI. Don’t neglect that! I use a $26 SunTerra 320 GPH fountain pump, and I don’t recommend anything much smaller because the pump needs to be sized large enough to overcome the substantial resistance of the wort chiller coils.
If your ice is free, like after a winter snowfall, you can use this method to do the entire chill process from boiling temperature to pitching temperature, but in most seasons when you need to buy (or make) ice, it’s cheaper to use tap water the “normal” and wasteful way first to chill the wort down to 100° F or so, and then move the tubing over to use recirculated ice water.
Unlike the usual immersion chilling methods, you are recirculating the ice water, so you can run this as fast as you like, or as fast as the pump will manage, which helps speed up the cooling process without wasting water. The ice cubes or slush ensure that the re-chill of warm return water is fast, much faster than with a prechiller in the ice bucket. All you have to do is keep the wort moving a bit by stirring (or the “Jamil” recirculation method) so that you move cooled wort away from the cold coils, but if you’re lazy, you don’t even have to do that, and you can just let this chiller run longer and use no more water and only pennies more electricity. A note on GFCI: A 120 volt electrical circuit like this, which is immersed in water, should either use a GFCI outlet or a circuit with GFCI breaker (I installed the former). If you don’t have that, buy a GFCI adapter or extension from Lowe’s or Home Depot. In the rare event a defect allows water to reach the electrical contacts inside the pump, the GFCI will trip and cut the power instead of turning the water, coils, and kettle into a shock hazard.
In summer with my 5-gallon batches, I use roughly an 8-pound bag of ice for ales and 12 pounds of ice for lagers. In my tests at home and one that I did at Flying Dog Brewery for a demo, we were able to chill 5 gallons of water from over 90° F down to 50° F in less than 15 minutes. Try beating that with just tap water! And our total water usage for that step? Only about three gallons – including the ice!
If you are currently using an immersion chiller for your wort, then when it comes time for an upgrade you should definitely consider upgrading to this recirculating ice-bath method. It’s simple, makes efficient use of water, and equipment cost is low.