I fly sparge directly into my boil kettle and in general I have the heat on while I'm doing this. When this was on my stove it wasn't powerful enough to get the water boiling before finishing the sparge so it saved me a bit of time. Now I have an outdoor burner that is very powerful.

I'm wondering is it ok to start it boiling while sparging or should I wait till sparging is done? Specifically, why should I do one or the other?

  • Great question.
    – brewchez
    Aug 15, 2011 at 0:44

2 Answers 2


It's totally fine. The ideal situation would be to have it come to a boil just as you stop sparging and close the valves. I'd experiment with collecting say a gallon and a half first, then fire up the kettle. Next time adjust the "kick-off" volume and start the fire then adjusting to get to a boil just as the sparge ends.

The concern with boiling to aggressively early on would be over wort darkening. I imagine it might be tough to calculate your boil off rate too that way.

It'll definitely save some time to have the wort heating to a boil while sparging. I think a lot of people do it that way.

If you do achieve boil prior to finishing the run off, I would just count it towards the a good hot break. I wouldn't start my hop timing and additions until I finished collecting all my volume. Again, hopefully you time it right so you have a good boil just as you finish collecting (or soon there after). I typically boil of 75 minutes anyway, "pre boiling for 15 minutes before I start into the 60 minute hopping schedule.

  • Yeah I could see that affecting the boil off, though I suppose additional water could be added. That's basically what I did today, heated it enough so that I could get to a boil shortly after I was done sparging Aug 15, 2011 at 3:46
  • It's fine to do whether you fly or batch sparge.
    – Denny Conn
    Jan 28, 2012 at 2:17
  • Dozens of home brewers I have seen start heating before sparge is complete.
  • No home brewers I have seen (out of dozens) attain a boil before sparge is complete.
  • Could get higher caramelization (could be good or bad) because your early runnings are going to be higher in sugar, and you've got a big flame under them.
  • Can save some time in your brew day.
  • Can cause a problem replicating recipe / documentation issue (you'd need special notation to document this boil time that wasn't really a boil because not all wort was present).
  • Lengthened boil could affect recipe in that more evaporation will occur.
  • You will be unable to get a true "pre-boil gravity" measurement.

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