Water volumes

To predict all the volumes for brewing process we need to know our equipment, decide the stage of mash thickness that we want to have,…

So, we can divide process into three parts:
1. Volume of strike water-V(SW) this is the water, where mashing process is done. Volume depends on desired mash thickness that usually varies between 2,1 and 3,1 L/kg or 1,0-1,5 qt/lb at homebrewers.
2. Volume of sparge water-V(SPW) this is the water that is used to sparge all the fermentable sugars from mash. Typically the sparge volume is about 4,2 L water/kg grain or 0,5 gal water/lb grain, but it depends on the mash thickness, becouse if we have mash thickness at very low level than the volume of sparge volume will be higher and vice versa.
3. Volume of total water needed for brewing-V(TO)-all volumes

Ok, becouse of losses during boiling the target pre-boil volume should be 20 % grater than wanted volume of beer:
during boiling the evaporation is approximately 2,1 L/h or 0,555 gal/h, and also we need to know that when boiling is over the wort has nearly 100 °C/212°F but we need to cool it down to cca 20°C/68°F, the shrinkage is 4 %.

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1. Units

Vsw (volume of strike water – water for mashing process) Units: L or gal
MT (mash thickness – it usually varies betwen 2,1-3,1 L/kg or 1,0-1,5 qt/lb) Units: L/kg or qt/lb
Wg (weight of grain) Units: kg or lb
Vag (volume of water absorbed by the grain) Units: L or gal
A (absorption – typically the value is 1,04 L/kg or 0,125 gal/lb) Units: L/kg or gal/lb
Vtm (total mash volume) Units: L or gal
Vg (volume of grain – typical values are 0,67 L/kg or 0,08 gal/lb) Units: L/kg or gal/lb
Vspw(volume of sparge water – general rule is to use 4,2 L/kg grain or 0,5 gal/lb grain, but it depends on mash thickness, that is why we calculate it usually) Units: L or gal
Vfr (volume of first running – this is the volume that we get at first running after mashing) Units: L or gal
Vaw (volume of any added water) Units: L or gal
Vlr (volume of liquid remaining in the bottom of the mash tun) Units: L or gal
Vor(volume of liquid remaining anywhere else) Units: L or gal
Vt (target pre-boil volume – it is typically 20% greater than target for end volume of beer, this volume is the volume before we start with boiling) Units: L or gal
Vto (total volume of water needed for brewing) Units: L or gal
Vamw (volume of additional mash water) Units: L or gal
Vpb (volume of added water pre-boil) Units: L or gal
Vpob (volume of added water post boil) Units: L or gal

2. Equations

Vsw = Wg x MT
Vag = A x Wg
Vtm = Vsw + Vg
Vfr = Vsw + Vaw – Vag – Vlr – Vor
Vspw = Vt – Vfr
Vto = Vsw + Vamw + Vspw + Vpb + Vpob
All the equations are the same, weather using metric or us system.

3. Calculations

Example recipe: 4kg/8,82lb of pale ale, 0,2kg/0,44lb cara malt 50, 0,2kg/0,44lb cara malt 120 and 0,05kg/0,11lb Mroost 1400 for end volume 20 L/5,28gal).

Step 1: we need to calculate volume of strike water  first (Vsw) to proceed with mashing, let’s pick desired mash thickness 3,1 L/kg1,5 qt/lb
V(SW) = W(G) x MT = (4 kg + 0,2 kg + 0,2 kg + 0,05 kg) x 3,1 L/kg = 13,8 L
V(SW) = W(G) x MT = (8,82 lb + 0,44 lb + 0,44 lb + 0,11 lb) x 1,5 qt/lb = 14,7 qt

Step 2: let’s calculate volume of sparge water now
first we will calculate volume of first runnings
Vfr = Vsw + Vaw – Vag – Vlr – Vor
Ok, we already calculated volume of strike water Vsw, we will not add any additional water to the mash, so Vaw is 0,0 L / 0,0 gal, volume of water absored by grain-need to be calculated,
Vag = A x Wg = 1,04 L/kg x (4 kg + 0,2 kg + 0,2 kg + 0,05 kg) = 4,63 L
Vag = A x Wg = 0,125 gal/lb x (8,82 lb + 0,44 lb + 0,44 lb + 0,11 lb) = 1,223 gal
volume of liquid remaining in the bottom of the mash tun Vlr is different from system to system, but at my mash tun this volume is 2 L / 0,53 gal, and volume of liquid remaining anywhere else – at my system is 0,1 L / 0,026 gal.

Now we have all the values to calculate volume of first runnings:
Vfr = 13,8 L + 0,0 L – 4,63 L – 2 L – 0,1 L = 7,07 L
Vfr = 3,68 gal + 0,0 gal – 1,223 gal – 0,53 gal – 0,026 gal = 1,901 gal

Calculation of volume sparge water:
Vspw = Vt – Vfr
Our goal is 20 L / 5,28 gal of beer, pre-boil volume should be approximately 20% greater value, that is why the equation is:
Vspw = Vt + Vt x 0,2 – Vfr =  20 L + 20 L x 0,2 – 7,07 L = 16,93 L
Vspw = Vt + Vt x 0,2 – Vfr = 5,28 gal + 5,28 gal x 0,2 – 1,901 gal = 4,435 gal

And all the water calculations are done!