For whatever reason, Beersmith decided to have me lauter my all-grain recipe with an exorbitant amount of water. I don't have the exact recipe in front of me at the moment (can provide details later if necessary), but from what I recall looking at the brew steps, I was aiming for a 6 gallon batch, and it had me mashing with 4.5 gallons, sparging with ~9. I knew something was off when I looked at the brew step that said I should end the boil with 7.5 gallons, to achieve a 6 gallon amount for fermentation.

I have no idea how these numbers came about, but I certainly did not sparge with all 9 gallons. Maybe 7-8, and my pre-boil gravity was well under what Beersmith estimated. It was a batch sparge, no mash out. Again, I can't provide specifics at this very moment, but instead of correcting that recipe, I was more curious about what can be done in the event that your pre-boil gravity is lower than expected?

In my case I had between 7 - 8 gallons going into the boil kettle, I just let it boil down for about 1 - 2 hours before I began my hop additions. In the long run, surprisingly I wound up at about 5.5 - 6 gallons of wort to go into the fermenter when it was all said and done, but what is the normal method for correcting an under-shot pre-boil gravity? Is sacrificing quantity the only way of correcting this sort of shortcoming?

  • Beersmith calculates the amount of sparge water based on values entered in the "equipment" that you chose in recipe design section. Wort gets left behind for varius reasons at different steps in the process: grain absorption, mash tun dead space, evaporation, trub loss, chiller loss, etc. You can specify all these values for your equipment. It takes a while tog dial in the correct values for your setup. Make a habit of measuring everything during your brew day and put the numbers back into Beersmith, so the volumes on your next brew session will be more accurate. Commented Mar 25, 2013 at 18:12
  • Yeah, I assumed the error was on my equipment settings. I haven't done a very thorough check of my setup to nail the correct values down, but I definitely need to make sure I get the right settings.
    – Scott
    Commented Mar 25, 2013 at 18:50
  • There is hope, Beersmith has been very accurate for me on how much sparge water to add, like Tobias said, keep measuring and updating Beersmith and it'll work out. Commented Mar 27, 2013 at 15:42

2 Answers 2


If your pre-boil gravity is low you can goose it with some DME or whatever fermentable sugar you prefer.

As to the issues with beersmith, its hard really to know without the recipe so when you have that throw it up and we can examine it more.

  • Ah, never thought of the DME, although I'd imagine if I'm too far off, adding DME to get it to the right gravity would also impart some off flavors. I'll post up the recipe when I get home this evening.
    – Scott
    Commented Mar 25, 2013 at 17:23
  • Yeah although I think the "Off" flavor would only come through if you are using an exorbitant amount...something to think about though. Commented Mar 25, 2013 at 17:52

I just let it boil down for about 1 - 2 hours before I began my hop additions. [...] but what is the normal method for correcting an under-shot pre-boil gravity?

Boiling for 1.5-2 hours is quite common. It sounds like the advice you got from Beersmith was correct. Your pre-boil volume is usually about 1.2-1.5 times your expected volume into the fermentor. I always boil for 90 mins, and 120 mins for pilsner, where I get typically 2-3 gallons of water boiled off. In your case, you had an extra gallon an a half. That does sound a touch excessive, but not unheard of. You can look at the equipment profile, particularly deadspace in the kettle and losses to trub and chiller - these are added to the pre-boil volume so you hit the right volume into the fermentor. Also double-check the configured boil time and boil-off rate, since that will also be taken into consideration.

Because of the diluted preboil wort, Beersmith also computes the pre-boil gravity, so you can check if you are on target. You expect the pre-boil gravity to be lower (around 70-80%) compared to your target OG.

  • I should clarify. The actual boil, with the hop schedule was for 90 minutes. Before that 90 minutes though, I had to boil it down for about an hour and a half to two. Thus, it was boiling total from 2.5 - 3 hours. Once I get home and can pull up the recipe, I'll post more concise details on quantities to see if it is indeed within reason. Thanks for the insight though.
    – Scott
    Commented Mar 25, 2013 at 19:27
  • Have you measured your boiloff rate during previous brews?
    – mdma
    Commented Mar 26, 2013 at 23:09

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