Help with understanding batch sparging measurements

OK, so last weekend I did a 10 gallon batch but I'm not exactly sure I got the water amounts right and I'm wondering how much I'm supposed to use and why?

I used 30 lb of grain and needed about 12 gallons pre boil according to pro mash. If that's the case, how much water should I have used with my mash and how much with my sparge? Dry grains will of course absorb water, so it's definitely not a cut and dry 6 for mash, 6 for sparge. How do I figure this out?

I always figure about 0.52 qt/lb absorption for the mash, and then whatever volume of sparge water I need to add to hit my preboil volume. So for a 13 lb grainbill, 6.25 gal preboil, and mashing at 1.25 qt/lb, you'll be figuring a hair over 4 gallons for your mash water, and 4 gallons for your sparge. The grain won't soak up anymore water after the first runnings are drained (or at least a negligible amount) so you can adjust the sparge water volume as you see necessary once you figure the volume of your first runnings.

~1 pint absorption per 1 pound of grain.

30lbs x 1/8 gallon = 3.75 gallons absorbed. 12 gallons preboil + 3.75 gallons lost = 15.75 gallons total water needed.

Then figure out your desired mash ratio, say 1.25 qts/lb. 30lbs x 1.25 qts/lb = 37.5 qts / 4 ~ 9.25 gallons.

So that leaves 15.75g - 9.25g ~ 6.5 gallons left for the sparge. But if you batch sparge, it's easier...just see what you collect after the mash, then subtract that from 12 gallons to get your sparge volume.

That sounds simple enough. What's an accurate way of measuring your pre boil wert? A stick with lines marked on it for certain measurements?

cokronk said:

That sounds simple enough. What's an accurate way of measuring your pre boil wert? A stick with lines marked on it for certain measurements?

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Yup, that's what I use. Not very precise though. Lots of guys have sight glasses on their kettles. Another simple option is just running off into a bucket with volume measurements.

cokronk said:

How do I figure this out?

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You can certainly figure it out w/ software or by hand if you know the maths and have the desire...A very simple method is just to measure your wort in the ketttle before the last sparge and subtract that from your preboil volume giving you the amount of wort needed to reach your preboil volume, this will be the same volume as needed for your last sparge...easy peasy.

So to put it into rough easy numbers, say for a 10 gallon batch you want 13 gal preboil, figuring on boiling off 2 gallons and losing a gallon to trub, leaving 10 gallons finished beer. If prior to your last sparge you have 9 in the kettle, the last sparge would be 13 minus 9, or 4 gallons.


With experience you will learn losses due to boiloff, trub/hops sludge and yeast cake to better figure for the final batch.