Water Lost in Spent Grains
While calculating the overall water necessary to conduct a full mash , batch sparge and boil it is important to note how much water will be lost in the spent grains. I use the basic equations below when calculating the amount of water necessary when brewing an all grain beer.
Amount of Water for Mash = (Pounds of Grain) x 1.25 quarts/pound (divide by 4 to get gallons)
Amount of Water to Batch Sparge with = (Final Boil Volume) + (Shrinkage/Evaporation) + (Equipment Losses) + (Spent Grains) – (Amount of Water for Mash)
From what I have experienced on my brewing rig spent grains absorb about 20% of there own weight in gallons, here is a chart that can be used for reference. This estimate is based on my single infusion mash with batch sparge in a 60 quart cooler with a grain crush around .039.
Total Grain Weight in Pounds x .20 = Approximate Gallons of Water Absorbed by the Grains
|Pounds of Grains||Gallons of Water Lost|