Brewing a concentrated wort

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Well-Known Member
Feb 1, 2011
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Hey guys,

So let me preface with I've searched and cant seem to find a solid answer to this. If this thread goes well, I'll be adding the info to the wiki.

I have been having an influx of demand for my beer (started military pilot training) and would like to boost my production.

I have a 15.5 gal keg MT and a 15 gal kettle which allow me to do a solid 11 gallon batch (limiting factor being the BK).

I am familiar with the calculations C1V1=C2V2 and know how to do the math. What I am wondering is if I use beersmith to calculate the grain bill for a 15 gallon batch, will I get the OG I am looking for? I fly sparge and wonder if I will extract enough sugar before my boiler fills up. Will my efficiency go way down?

Also, to my knowledge IBUs are linear. So if I use enough hops for a 15 gal batch during the boil for a 10 gal batch, everything will work out, right?

To summarize, will a beersmith recipe for a 15 gal batch:
a) Give me a concentrated enough wort to dilute to 15 gal (from 10 gal)?
b) Give me the IBUs calculated for 15 gal (from 10 gal)?

Thanks in advance. I hope this topic hasnt already been beaten to death.



Well-Known Member
Jan 12, 2010
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a) yes, but most take an efficiency hit when brewing bigger beers. For me, I drop to about 65% from 75%. you can either boil longer to make up for the extra sparge, add extract/sugar, or add more grain to account for the loss.

b) sorta. due the the more concentrated wort, the IBUs will drop a bit. however, you probably won't be able to notice much of the difference.


Vendor and Brewer
HBT Sponsor
Aug 3, 2006
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Whitehouse Station
Yes, you'll take an efficiency hit due to the higher gravity in the mash but also due to the fact that part of your total batch volume will be water added back in.

The way I'd handle it is to sparge enough for about 16 gallons of runoff. Start boiling with about 10 gallons in the kettle, hit the initial hot break point and slowly feed it with more of the runoff until you're running a rolling boil without boilover. If you manage it just right, you should be able to integrate the full amount of runoff into the kettle by the end of the boil and end up with probably 14.5 gallons chilled.

Easier? Get a 20 gallon kettle.