Batch Sparge Bug

I ran across this the other day.  The batch sparge volumes are not calculated correctly.
I verified the error by doing the following:
Create new recipe
Add 24.5 lbs of any base malt, set the batch size to 10.5 lb and picked a profile such as "15 gal kettle, 12 gal igloo cooler)
Went to mash details page and selected "single infusion, full body, Batch sparge".  The default result is
"drain mash tun, batch sparge with 2 steps (8.65 gal, 4.46 gal) of 168F water"

With those volumes alone, you'd have 13.37 gal of water, let alone what would drain out of the mash tun
If you go to the "water volumes" page, you'd see
Water available from mash: 4.72 gal
Sparge vol: 8.65 gal
est pre-boil vol: 12.57 gal

Can anyone else replicate this?

Are you allowing for absorption?

Yes.  At least, that's what Beersmith seems to state.  Going to the water usage tab, it shows grain absorption as 2.94 gal.

The plot thickens!
I dug a little bit and found the following (hope this is a clue Brad!)
The default setting for this mash profile is to have the "batch sparge using batches that fill __" equal to 90% and have the checkbox ticked.  This yields the erroneous "drain mash tun, batch sparge with 2 steps (8.65 gal, 4.46 gal) of 168F water"
If the setting is changed to 100%, the following, more correct version is returned:
"drain mash tun, batch sparge with 2 steps (1.97 gal, 6.68 gal) of 168F water"

I did some iterating, and found a radical difference when shifting between 96 and 97%

Has anyone tried to verify this with the values I previously posted?

I don't know if its a bug or I just don't know what I'm doing, but something isn't calculating right for me either.

18lbs of grain and I want to have a batch size of 5.5 gallons and a boil of 60 minutes.

It tells me to add 5.62 gallons for the mash and then batch sparge in 2 steps - .48 gallons and then 3.95 gallons for a total of 10.05 gallons of water.  Grain absorption is calculated to be 2.16 gallons.  So, boil volume would be 7.89 gallons.


How am I supposed to boil off 2.39 gallons in 60 minutes?  Do I have something misconfigured?

That would be 30%+ boil-off in 60 minutes.

So, is what I'm experiencing real with these volumes?  Or do I have something misconfigured?

I did 3 brews yesterday and am 100% convinced that the sparge water volumes are dead wrong.    Mash volumes appear to be fine.  When figuring out the sparge, I use the boil off tool to determine how much water I need to sparge with.  If I didn't do this... I would end up with way too much of a boil volume and thus throwing off my ending batch size.

I'd love for a programmer or someone else to confirm the above issue.

I am not the programmer.  I have long been mystified on how BS calculates the water volumes and truthfully, it seems to be too much information and often contradicts itself.  For example, in the recipe/water volume tab, it says I need 9.19 Gallon of strike water (total mash water) and 6.28 gallons of sparge volume (which the mouseover says sparge water needed).    Total water above that is in agreement at 15.46 g.  When you close that then look at the classic brewsheet or classic report reports, the sparge water changes to 6.27 + 3.14.  I have no idea where the +3.14 comes from.    Now the water needed tool says I need 6.28 as well, so they are in agreement.

I duplicated your grain amount.  Comparing BS2 to BS1.4 to my own simple calculator finds them all in basic agreement.    I have done a lot of tweaking of BS to achieve the results I want.  I have custom equipment and mash profiles.  Basically, I know what preboil volumes I need for a batch and keep tweaking BS until it aligns with reality.  For me, software tools are help get close but you need to know what your system does and adjust the software to match, not the other way around.

Beersmith 2
Mash or Steep Grains

  Mash Ingredients
Amt Name Type # %/IBU
24 lbs 8.0 oz Pale Malt (2 Row) US (2.0 SRM) Grain 1 100.0 %

  Mash Steps
Name Description Step Temperature Step Time
Mash In Add 36.75 qt of water at 166.2 F 156.0 F 45 min

  Drain mash tun, Batch sparge with 2 steps (6.27gal, 3.14gal) of 168.0 F water

total, 18.5 gallons

Beersmith 1.4

Mash or Steep Grains

  Ingredients for Mashing Amount Item Type % or IBU
24.50 lb Pale Malt (2 Row) US (2.0 SRM) Grain 100.00 %


  Single Infusion, Full Body, Batch Sparge Step Time Name Description Step Temp
45 min Mash In Add 36.75 qt of water at 168.4 F 158.0 F

  Drain Mash Tun
Batch Sparge Round 1: Sparge with 6.85 gal of 168.0 F water
Batch Sparge Round 2: Sparge with 3.43 gal of 168.0 F water

total 19.5 gallons

My web calculator

Calculate mash and sparge water volumes based on information in Brew Your Own and around the web
 
Mash Water 9.2
Sparge Water 8.7
Total Water Needed 17.9 gallons

When I said "programmer", I was more or less referring to programmer(s) of the beersmith program and for them to explain how the mash water + sparge water amounts are calculated.

After messing with it a bit more, I realize that the default profiles didn't match what my equipment actually does.  This of course is a complete BS rookie mistake.  I also generally make my recipes for 5.5+ gallons.  I'd rather toss out a little when I keg rather than start with less than a corney can hold.

However, I would still like to know what the math looks like and what variables I need to take into consideration.  Is this "spelled out" anywhere?

Hi,
  I did find a bug in the batch sparge routines (related to a fairly rare condition where the mash tun has more water in the first step than needed for even runnings).  It will be corrected in a few days in the new release.

  The basic algorithm for batch sparging (at least with the default profiles) is to try to create "equal runnings" for the batch sparge - which means an equal amount of wort coming out of the mash tun after each sparge batch.  This is actually best for overall efficiency.  Some people get confused because this means that the first step may have little actual sparge water as you are draining the water already in the mash.

Brad