Calculating All Grain Mash and Sparge Water Volumes
Start From The Bottom up
Calculate what is left behind
These variables can be calculated by the brewing methods outlined in the recipe or by use of the equipment. These calculations will be different because equipment profiles and brewing methods are different for each brewer. Make note of each of these volumes.
- Wort left in the equipment – Example chillers, brew kettle, fermenter
- Wort absorbed by hops and protein break
- Evaporation losses during the boil
- Liquid left behind in lines and “dead space” in the hot liquor tank, mash tun, or other sparge equipment
- Liquid absorbed by grain
Water off sets (Adding additional water to the mash or fermenter)
- Mixing strike water with the grains at the start of mashing
- Sparge water added to the mash to “rinse” and extract remaining converted sugars
- Water added to the kettle to achieve target pre-boil gravity
- Water added after the boil either to the kettle or fermenter to achieve target post boil volume
Strike Water (Initial mashing water)
Mashing is the process where we take the crushed malt and using enzymes break down starches into sugars for fermentation. Mash thickness can vary based on the recipe, the equipment and brewing methods used. The typical home brewer will be using a range of 1-1.5 quarts of water per pound of grain. Don’t stress mash thickness at this time, find a ratio that will work for your equipment. The average ratio is 1.25qts/pound. The formula for mashing will vary depending on the amount of grain used.
Strike Water Formula
Strike water volume = weight of grain X Desired mash thickness
Mash thickness of 1.25qts/pound with a grain bill of 10lbs would result in a strike water volume of 12.5qts (3.12gallons)
Take it all in
Grain absorption is a factor we need to work into our formula, for this we use an average of .5 quarts per pound of grain. This average is used because of the varying absorption of certain grains and adjuncts.
Using our example recipe above we can calculate the grain absorption rate would be 5 quarts (1.25gallons).
Where are we now and can we hold it?
We have the volume of mash water we need but can our mash tun hold it all?
Mash Water Volume = Strike Water Volume + Grain absorption
[ 17.5Qts (3.92 gallons) ] = [ 12.5Qts (3.12 gallons) ] + [ 5Qts (1.25 gallons) ]
We now have to calculate the displacement of the grain to ensure our mash tun can hold it all together. Grain displacement will depend on the amount of grain in the grist bill. A reasonable average is .32 quarts of per pound of displacement. Continuing our example above we can calculate the mash tun size required.
Total Mash Tun Volume = Volume of strike water + Volume of Grain
[ 15.7Qts (3.92 gallons) ] = [ 12.5Qts (3.12 gallons) ] + [ 3.2Qts (0.8 gallons) ]
This is the process of rinsing the remaining sugars from the grain. This step is important as it helps determine the pre-boil gravity. Batch sparging is the easiest method if you are new to all grain brewing. However not all mash tuns will have the capacity to sparge the volumes it needs to rinse the grain. We will discuss splitting the sparge later in the instructions.
Before we can calculate the volumes of sparge we need to know how much run off we collected from the mash tun. We also need to know our losses. Using the example above we are going to use 1 Quart to account for liquid left behind in the mash tun.
Volume of first runnings = Strike water Volume + additional water added to the mash – Water absorbed by grain – Volume of liquid in equipment
6.1 Quarts = [ 12.5qts ] + [ 0qts ]- [ 5qts ] – [ 1qts ]
Whether you are batch sparging or fly sparging the formula is the same for calculating sparge water.
Total Volume of Sparge Water = Target Pre-Boil Volume – Volume of First Runnings
Using our example above we need to collect 28 Qts (7 gallons) pre-boil volume. This volume accounts for the amount of Wort going into our ferementer + Boil off + Equipment losses
Currently we have collected 6.1 Qts so that leaves 21.9 Qts (5.4 gallons) needed for sparging.
Bring it all together
Still using our example above we can bring all the formulas together to calculate the needed water.
Total volume of water needed = Volume of strike water + volume of any additional mash water infusions + volume of sparge water (including any sparge water vessel dead space) + any water added to the kettle pre-boil + any water added to the kettle or fermenter post-boil
12.5 qts. + 21.7 qts. = 34.2 quarts