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Is there anything wrong with simply letting the water you add to top off your wort do the chilling to bring it to yeast pitching temperature?

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I answered below, but noticed the question had been answered before with some good tips. Never use commercial ice, and always know your ice was made from boiled water, seems to be the main take-away message. –  Chino Brews Dec 26 '13 at 4:37
    
Thanks for that answer, it's helpful. I actually made my own wort chiller (coppere coils) and used it in about 3 batches so far. I also have a charcoal filter on a devoted water source for all my brewing water. The problem I found using the wort chiller was that, after having chilled the wort to pitching temp, the top off water I was adding was too cold, and would bring the temp of the wort too low to pitch. that's why I started skipping the chilleer and just using the cold water top off to bring my wort to pitching temp. My only question now is that my home brew centre recommends a pitching t –  user6192 Dec 26 '13 at 17:48
    
@Andy, you did not finish your follow up question. As far as your problem of your wort getting too cold, I advise you create a calibrated dipstick. Just take a chopstick or unfinished wooden dowel and your brew kettle. Fill up the kettle about liter at a time, and mark the level on your dipstick. Now, when you are cooling, you will know how much wort you have, and how much topping off water you need. Then measure the temp of your topping off water. With that info you can calculate how much to cool your wort as follows... –  Chino Brews Dec 28 '13 at 3:25
    
Target temp to cool wort = [(Target pitching temp * Target volume) – (Top-off water temp * Top-off water volume)]/ Post-boil volume If your Target volume is 20L, and your Post boil volume is 8L, then your Top-off volume is 20L minus 8L of wort in kettle = 12L. If we assume your target pitching temp is 19°C, and your top-off water is 15°C, then your target wort temp = [(19°C * 20L)-(15°C * 12L)]/8L = [380 - 180] / 8 = 200 / 8 = 25°C. So use chiller until wort is around 25-26°C, rack the wort to the fementer, top off with 12L of 15°C water, pitch your yeast, and aerate. –  Chino Brews Dec 28 '13 at 3:55

3 Answers 3

No, there is nothing necessarily wrong about using topping off water to cool your wort. But there normally isn't enough topping off water to cool the wort to pitching temperature by itself without applying an additional cooling method (the math is below). One reason to cool quickly to ideal yeast-pitching temp is to allow the yeast to get a nice head start before bacteria can get a foothold. Wort is an excellent bacteria breeding medium.

Let's assume yeast-pitching temperature is 70°F (20°C) or less.

Example 1: If you do a partial boil and end up with 2.5 gallons (9.5 L) of wort at 210°F (99°C) and top off with 2.5 gallons (9.5 L) of water cooled in the refrigerator to 40°F (4.5°C), you will only cool your combined liquid volume to 125°F (52°C). Your wort is now lingering at ideal bacteria breeding temperature.

I have a friend who has probably made at least 100 partial-boil, extract recipe kits over a 15+ year homebrewing career. He dumps tap water ice cubes into his hot wort, and claims to have had very few infected batches. Even if you are not worried about topping off with plain-old tap water (frozen or liquid), ice alone is not enough to get you to yeast pitching temp. My friend simultaneously uses a cold water bath in his kitchen sink.

Example 2: If you assume only 2.0 gallons (8.4 L) of wort at 210°F (99°C) and top off with 25 lbs. (11.3 kg) of ice at 5°F (-15°C), that gets you to 5.0 gallons (19 L) of wort that is still too hot for ideal yeast pitching: 87°F (30.5°C).

So you could then wait out the last 17 degrees F (9.5 degrees C), or also do a cold water bath.

BTW, many experienced homebrewers recommend that you use non-chlorinated or de-chlorinated, yet sanitary, water for topping off (and your boil). Chlorine in water leads to one of the most common flaws of homebrewed beer -- medicinal or chloraseptic off-flavors. You could use bottled water or reverse osmosis water, install a charcoal filter, pre-boil and chill your tap water, or use a campden tablet, to avoid chlorine in the water.

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Alton Brown dumps his boiling wort onto a brick of ice! Clearly there is more than one way to skin this cat.

Topping off is perfectly legit, however I will note that my immersion chiller is probably my single favorite purchase amongst all my gear.

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I like all the ideas above and I and going to be trying some of them. So far, I usually put my top off water in the fridge at least over night. I top off right away and that usually gets the temp pretty close to pitching temp, around 100-105. (I usually brew ales with a pitch temp of less than 90). I then have a utility sink (or a tub would work) filled with ice water that i set the wort bucket or pot in. Obviously you want to be careful that the water doesnt rise high enough to enter your wort.

I usually dont have to wait much more than 90 minutes at the very most!

so far, no complaints :)

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