I just purchased my first kit and am about to brew it (tonight!).

The instructions provided indicate that after cooling the wort and tranfering it to the sanitized carboy I need to top it off with cold water. It seems like this is just asking to introduce non-desirable organism to the beer. (or not quite yet, beer).

My questions:

1) Should I boil the top-off water and cool it, before adding?
2) If not, why?

  • 1
    The other posters have your primary topic covered, but: "not quite yet beer" is called "wort". :)
    – jsled
    Commented Jul 11, 2011 at 18:33

3 Answers 3


When I did extract I tended to just go from the tap right into the fermentor with the wort. I can't say that I ever had a bad batch because of it. But it certainly can happen. If you have a way to boil water for 15 minutes, then store it in a sanitary and sealed contain while it cools back down to a useable temperature...that is the safer way to go.

If you are pitching enough yeast then its probably not a huge concern as you are getting started. And if this is your first batch I bet your LHBS has given you one packet of yeast or a tube of yeast and that's it. WHICH IS FINE FOR NOW, don't fret over the amount of yeast to pitch yet.

I say to just go for it unless your water comes from a well or something. Municipal tap water should be pretty clean. If you pick up a contaminant its likely happening right at the faucet, not from in the line. Just be sure you don't have dirty dishes and sponges splashing around in the sink as you get the water for top off.

I think you'll be fine from the tap until you are ready to move up a little bit in techniques and process.

  • Great! Thanks so much. Also, thanks for fixing my tags. Commented Jul 11, 2011 at 18:04
  • @brewchez I would be concerned about the effects of chlorinated tap-water, which would inhibit yeast growth (although Cl can be evaporated with time or heat). Filtered water may be a better idea. Commented Jul 11, 2011 at 22:51
  • @david I agree, but for the first batch things will work out. Start worrying about other things later I say.
    – brewchez
    Commented Jul 12, 2011 at 1:56

When I did extract, we always used a jug spring water to top off the extra few gallons. You can sanitize the bottle mouth with some StarSan or other sanitizing solution, and then just pour the bottle in. You can also keep the jug in the fridge prior to use to cool your wort when you add it. This way you avoid boiling anything, but are still pretty safe from contaminants.

  • Yup, its safe to assume a sealed jug of water is bacteria free. Or at least "free enough" to brew with. I've topped off with jug water many, many times.
    – GHP
    Commented Jul 11, 2011 at 20:12
  • This has been my method ever since I started. I bought sealed spring water and used that (I didnt even sanitize the tops) I have since started going to the grocery store and just use one of those water refilling stations because it costs even less. To this day I have had no ill reactions from this method after 30 something batches.
    – Bullet86
    Commented Jul 15, 2011 at 4:25

Great question. I have never topped-off from tap water for paranoia of contamination of the final batch. Perhaps the likelihood of contamination is very low, but why take the risk? Also, the more water you are topping off with, the greater your risk increases. So, to answer your question I personally would boil and cool your top-off water, or use bottled water from an unopened bottle.

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