Sparge Water and Pre-Boil Volume
Splits the brewing water into mash water, grain absorption, first runnings, and sparge for a pre-boil target.
Example
You enter
- Grain weight (lb) 542
- Mash thickness (qt per lb) 1.25
- Grain absorption (gal per lb) 0.125
- Pre-boil volume target (gal) 350
- Vessel deadspace (gal) 5
- Stronger grain bill to compare (lb) 850
You get
- Mash water 169.4 gal
- Kept by the grain 67.8 gal -- 16% of every gallon heated
- First runnings (before the tun deadspace) 101.6 gal
- Sparge water 253.375
- Total water 422.8 gal
- Alternative sparge (gal) 195.625
Checked against published worked examples from: Brew Your Own.
Details, formula, and sources
ScopeThe worked 542 lb grist loses 68 gal to the spent grain, 16% of every gallon heated, and the sparge delivers 71% of the runoff. At 850 lb the sparge shrinks 23% -- why efficiency falls as gravity rises.
Formula or tablemash water = G x R / 4; absorbed = G x absorption; first runnings = mash water - absorbed; sparge = pre-boil target - first runnings + deadspace.
Source and editionVolume bookkeeping, with grain absorption commonly 0.10 to 0.13 gal per lb. The brewery's own measured runoff governs.
Free accessPublic arithmetic.
What governsEstimate. AHJ and licensed professional govern.
API field namesgrain_weight_lb, mash_thickness_qt_per_lb, absorption_gal_per_lb, preboil_volume_gal, deadspace_gal, alternative_grain_weight_lb, mash_water_gal, absorbed_gal, first_runnings_gal, sparge_gal, total_water_gal, alternative_sparge_gal
- Absorption varies with the malt, the crush, and how hard the bed is drainedbrewery measurement