Water Amounts

Calculating All Grain Water Volumes – an Introduction

Brendan Mashing Image

By Oscar Casley

When you work at a homebrew shop you occasionally forget how it feels to be starting out. One of the things we find ourselves regularly explaining is water volumes for all grain brewing. It’s something that seems very simple now, but we remember when it sounded a bit like witchcraft.

Here is a quick idea of the calculations we use when we’re brewing at home.

A basic intro to water volumes when brewing with grain:

Note: These calculations will be done assuming the brewer is brewing a standard 20L batch. Things get different with larger brews.

The Universally True Calculations:

-    Grain absorbs around 1L of water per kilo of grain

-    During a 1hour boil about 2L – 6L will evaporate (this will change system to system)

-    In a 20L batch you will lose about 2L - 3L in trub (hops, proteins and other solids) and in some extreme cases, more.

With these three rules in mind, water loss in a brew with 5kg of grain and a boil time of 1 hour will be around 12L

    5kg of grain = ~5L of water loss
    1 hour boil = ~4L of water loss
    Trub loss = ~3L of water loss
    Total water loss = ~12L

If you only use 20L of water and 5kg of grain you’ll have 8L at the end of the boil, which isn’t enough if you’re aiming for 20L final volume. This is where you need to do your calculations.

Using the numbers above if you plan to begin the fermentation with a total volume of 20L you need to add some water. For this simple example you will need to add 12L to make up the lost water, giving an overall water volume of 32L. But where is the extra water added?

This is where things get subjective. It really depends on your brewing system and how you are brewing. Most brews you do will split the water into two segments:

-    Strike Water (the water that you use for your mash)
-    Sparge Water (the water you use to rinse the grains after the mash)

In brew in a bag you there are a couple of options for sparging. You will use most of your water for the mash, only saving a small percentage of it for sparging or none at all. The main reason you don’t use much sparge water for this method is that it is very difficult to sparge through the bag after it has been removed from the kettle. An example of water usage for a 20L brew in a bag brew with 5kg of grain with sparging might be:

    27L of strike water
    5L of sparge water
    Total water volume: 32L

And without sparging – fairly obviously:

    32L of strike water
    Total water volume: 32L

Single vessel systems like the Braumeister, Brewzilla or Guten are easier to sparge but require a lot of strike water and so an example of water volumes might be:

    25L of strike water
    7L of sparge water
    Total water volume: 32L

And lastly, in a three vessel system, you are able to use a sparging method called ‘fly-sparging’ where the sparge water is slowly moved through the grain as you are collecting the wort. This slow process means you can use more sparge water and less strike water. This is beneficial because it means you can use a more efficient water/grain ratio during the mash (2.5L per kilo of grain) and usually rinse more from the grain during the sparge. For a three vessel brew you might end up splitting your water like this:

    12.5L of strike water (2.5L per kilo)
    19.5L of sparge water
    Total water volume: 32L

With those figures in mind let’s put it to practice with one of our All Grain Kit recipes:

Heifervision Wheat Beer:

2.25kg Pilsner Malt
2.25kg Wheat Malt
.250g Acidulated Malt

Batch size: 20L
Total grain: 4.75kg

The grain will absorb 1L per kilo which is 4.75L. You’ll lose another lose another ~4L in the boil and about 3L to trub. Aiming for a final volume of 20L the following are the calculations:

    20L + 4.75L (grain absorption) = 24.75L
    24.75L + 4L (evaporation during boil) = 28.75L
    28.75 + 3L (trub loss) = 31.75

Therefore, a total of 31.75L of water is needed for this beer. How it is split into Strike and Sparge water will be based on the system you’re using. If it’s brew in a bag with a 5 litre sparge it will look like this:

    26.75L of strike water
    5L of sparge water
    Total water volume: 31.75L

On a three vessel system it will look like this:

    11.87L of strike water (2.5L per kilo)
    19.88L of sparge water
    Total water volume 31.75

This is a good starting point for calculating your water volume for your all grain brews, but it’s just a start. There are other water losses you may want to keep in mind. These will be very specific to your system and recipe. You can choose to add them to your calculations, or just let them slide.

The Still Important but More Subjective Calculations:

-    Deadspace: this one is probably the most important-non-important one to figure out for your system. It is the places in your system where water gets trapped and will not make it into the final volume, eg. the space under your tap output. Things like pick up tubes can help but there’ll always be some left. You can work out this amount by filling up your vessels with a set amount of water and then pouring it out through the taps, the missing amount will be your deadspace and you can add it to the above calculations. This can range from 2L - 10L on some systems.

-    Hop pellets absorb about 1L per kilo too, but this is only something that I take into consideration if I’m doing a beer with a lot of hops (200g - 500g). Dried hop flowers on the other hand absorb a LOT of liquid, about 4.8L per kilo but are more rarely used.
If you are finding you’re having significant loss to these things, you may want to scale your recipe up a few litres so that your final beer isn’t affected too much by it.
Finally, a good thing to remember is that it is very easy to top up your wort at the end of the boil and much harder to boil off wort. We tend to veer towards using less water in the mash and sparge so that we don’t have to sit around while the wort evaporates off to get to my desired volume.
Hopefully this will help clear some things up and make brewday a bit easier for you. 
We believe it’s good to know these calculations even if you do use online calculators. You can quickly make sure the calculations are in the ballpark and if something goes wrong you can quite easily fix it.

Cheers and remember if you’re panicking RDWHAH(TCG&G) (Relax Don’t Worry Have A Homebrew (Then Call Grain & Grape))