I have made a few batches of beer from those home brew kits sold at Brew n Grow. When I cook the beer, I only am boiling 2.5 gallons instead of the whole 5, per instructions, and then I add the other 2.5 gallons from my tap water. My question is, is they recommend a wort chiller. When I add the 2.5 gallons to get my total of 5 gallons, it naturally cools down the beer because the tap water is cold. What advantages does the wort chiller have? I suppose the tap water doesn't get it all the way cool, but does a great portion of the cooling, because basically it is direct cooling as opposed to heat transfer cooling through a copper tube. Does adding the 2.5 gallons of cold tap water introduce potential bacteria into my wort??

Any answers would be greatly appreciated!


  • To piggy back off this question... My friend and I use store-bought ice to cool our 2.5gal boils. Is there any reason this is less than ideal? We dump the freshly boiled wort onto the ice in our primary fermenter and then add as much cold tap water as it takes to get us to 5.25 gallons. (The reason for the extra .25gal: We are bad at siphoning off the beer for secondary fermentation, and we normally spill a little during bottling because we are usually drunk.
    – BryceH
    Feb 26, 2013 at 14:48

3 Answers 3


If you're doing 2.5 gallon boils, and then adding another 2.5 gallons of (say) 55F tap water, then you're final temperature will be around 133F - the mid point of 212 and 55. For ales, pitching temperature is recommended at 75F, so you'll need to leave the wort for a few hours to naturally cool, or submerse in an ice bath to accelerate the cooling.

If you're happy doing that then you don't need a separate chiller. A wort chiller will allow you to cool the 2.5 gallons in just a few minutes, but it might be overkill. More equipment to store, clean and sanitize.

As to bacteria, you'll need to get a water report to see how much bacteria is in the water. There may be some bacteria, if not directly from the water itself, then from the faucet. However, it's rarely enough to noticeably contaminate the beer since the yeast quickly make the wort an unpleasant environment for the bacteria. Since you are already a few batches in, if there was a problem with the water, you would have noticed it by now!


Its not recommended to add hot wort to a glass carboy or plastic bucket either as the glass could crack or the bucket melt. I go 2.5 gal boils too, and simply set it in the sink with some ice and cold water around it (cover the boil pot with a lid to reduce contamination), and let it cool to 70 degrees. Then add it to my carboy and add the additional 2.5 gallons.

No need for a wort chiller for a batch that small. Now for all grain brewing over 5 gallons, I can see the need.

  • you can add 2.5 gallons of cold water to the bucket first, so the bucket never gets above 130 degrees - as long as you're below 160 the bucket will be fine.
    – mdma
    Feb 6, 2012 at 18:13

These above answers are all correct and very useful. In addition, I did learn a rule of thumb in my travels...here comes...the size of my partial boils is based on the amount of extract, one gallon of water for each 2 # of extract. So my partial boils usually are around 4 gallons. I do not use a chiller, but lots of ice in a bath. Say if you have a recipe calling for 8 # of extract, and you are only comfortable with a 3 gallon boil, add 6# of extract at the beginning of the boil, and add the rest with 10-15 minutes left. This method alledgedly prevents overconcentration and improves quality.

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