I was asked this and didnt have a definite answer but I thought for a 15 gallon batch you would need at least 17.5 gallon of water which that alone would make the 15.5 keggle useless for a batch of 15 gallons ..
Well, you can start with 12 gallons for the boil, and end up with 10.5 finished gallons. Some people would then add some water (and/or DME) to get up to 15 gallons. I have never done that, but I'm sure it's possible.
It works for that big brewer in St Louis.
I giggled when I initially read this, because I knew it would create controversy over how vigorously you boil and such. But then I got to thinking "Is there a cut and dry answer?" Yes, there is.
Ignoring all else, the expansion rate of water when heated to boiling is approximately 4%
15.0 * 1.04 = 15.6 gallons
So the only possible way to pull this feat off would be to top off with water after the fact ;-)
You could always add a little water throughout the boil to keep it at 14-14.5 gallons (a pint here a pint there). Then just add the last little bit to hit 15 gallons at the end.
Not if it was hot (almost boiling) water. Like from a "hot-pot" kettle.
Sooooooo it is possible ......but you'll be making a 12 gallon batch with 15 gallon grain bill making your wort concentrated and then add three gallons of chilled water helping you cool your wort to pitch?
If it was at a full boil and did not stop the wort from boiling, then yes that would work. Of if it was an African Swallow.
I don't see a reason that wouldn't work unless there is a chemical reaction I am missing.
There are only two considerations I can think of. One is maillard reactions- so if you were doing, say a Scottish 80 +/-, or another beer where you wanted to really have toasty maillard reactions it could be an issue. I think that's a very minor concern, though, and really nothing to worry about.
The other is hops utilization. If you were making a 75 IBU beer, I don't think it would be possible to do that with the addition of three gallons of water (1/5 of the volume).
Otherwise, I can't see an issue.
...The other is hops utilization. If you were making a 75 IBU beer, I don't think it would be possible to do that with the addition of three gallons of water (1/5 of the volume).
Otherwise, I can't see an issue.
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