# 🍺 Top-down Brew: Batch sparge volume calculator

## Purpose: Determine the volume of water additions needed for batch sparging

Grain weight (pounds or kilograms)
Strike water (gallons or liters)
Step water (optional; gallons or liters)
Water/grain absorption (gallons/lb or liters/kilogram)
Target wort boil volume (gallons or liters) Runnings: one two three Units: US units Metric units

Results: *** Waiting for results ***

## Notes:

Batch sparging rinses sugars from the mash by introducing the sparge water in large volumes. The optimal batch sparge approach is equally sized running volumes when two or more runnings are performed. This calculator estimates the optimal size of the water additions.

The formulas for the amount of water needed are ...

- First sparge water volume: = (TargetVolume / NumberRuns) - ((StrikeWaterVolume + StepWaterVolume) - (GrainWeight * WaterAbsorptionRatio))
- Second and third volumes: = TargetVolume / NumberRuns

For the first running, the left side of the formula determines equally-sized run volumes. The right side of the formula determines the amount of additional sparge water needed based on the volume of strike water plus step mash water minus water lost due to absorption by the grain bed. The second or third sparge water additions are half or one-third, respectively, of the target volume. Water absorption is unimportant for these second or third runnings because the water absorption loss has already occurred in the first step.

The standard batch sparge calculation assumes a mash thickness of 1.0 to 1.5 quarts per pound (2.1 to 3.1 l/kg) and equally-sized running volumes. However, multiple step water additions or brew-in-a-bag type approaches might use a much thinner mash. The calculator adapts to these thin mash situations when two or three runnings are desired by adjusting the additional running volume downward to compensate for the extra volume collected from the first running.

The sources use a water absorption ratio varying from .10 to .12 gallons/pound (.834 liters/kg to 1.0 liters/kg). If your total runnings are short of the target volume, it's likely that your system is retaining more water, such as water lost beneath false bottoms. The solution is to adjust the water absorption factor up just a bit, such as going from .10 to .12 gallons/pound, for the next batch.

A three step batch sparge is additional work that doesn't produce a very large increase in mash efficiency. Two runnings are probably the best choice for most situations. A third running might be useful though if the mash tun size is too small to accommodate the mash plus sparge water for a one or two step process. A related calculator on mash volume can be used to determine if the mash tun is sufficiently large.

## Sources

www.dennybrew.com Cheap 'n Easy Batch Sparge Brewing

Beechum, D. & Conn, D. (2020; January-February) Sparge ho! The many ways of rinsing grain beds (or not). BYO 79-81.

Conn, D. (2004; January-February) Cheap and Easy Batch Sparging, BYO.