Calculating Water Amounts

Introduction

This post is going to be about calculating the amount of water needed to brew a specific volume of beer  using a specific amount of grains on my specific system.  This is important because everyone's system is different.  This is the reason for the previous post where I calculated specific values for my system - values that will be used in my water amount calculations.  Before calculating my water amounts, let me quickly go over the details/reasons for my brewing posts....

Reason for Brewing Posts

I believe I mentioned this previously, but let me again state that these posts are not a basic step-by-step how to brew.  There are plenty of great resources for this, and I think the best place to start is with Palmer's book How To Brew.  This book is great for both the beginning brewer and the advanced brewer.  In fact, I am writing these posts because there is so much information out there.  I read enough to successfully brew a couple of batches of beer, and now I need to advance towards brewing better.  I am not an expert, but I am simply detailing my journey of trying to become one.  My hope is that someone smarter will correct my mistakes and answer my questions.

Some of the topics I intend to cover are water amounts needed to brew, how to formulate a recipe, calculating efficiencies, yeast starters, equipment and software tools, water reports, water modifications and possibly even writing my own software tools.  Hopefully we will all learn something as we go along (otherwise this is a complete waste of time when I could be brewing instead).

On to Calculating Water Amounts...

So I have brewed two batches of beer so far.  They were both supposed to be five gallons and they were both short on that amount.  I don't even want to count my first batch since it really was a learning batch; trying to put into practice the loads of information I had crammed into my poor brain.  I learned a lot - mainly information in the "what not to do" category.

So let me go through my water calculation that I have created.  I will know how accurate this is when I brew my next batch, and I will post those results at that time.  For now, here are the parameters we have:

• Target Batch Size: 5 gallons
• Total Grain Weight: 9.5 pounds
• Boil Time: 80 minutes

From the previous post, we saw that during a 60 minute boil, I will lose 1 gallon and 3 quarts or 7 quarts per hour.  If I divide the 7 quarts by 60, I will get the number of quarts per minute:

7 qt. / 60 min. = 0.117 qt/min

So if I have an 80 minute boil, I should lose:

80 min * 0.117 qt/min = 9.36 quarts or about 2.34 gallons

OK, so let's start with our final target volume and start moving backwards through the process.  We are interested in tracking the following volumes: Final volume (Vfinal), Volume in fermenter (Vferment), Volume post-boil (Vpostboil), Volume pre-boil (Vpreboil), Total volume needed (Vtotal).

Vfinal = 5 gal.

• Add any beer lost while bottling.  This is any beer caught in the settled yeast and equipment dead space.  I am guessing at this number, and will need to adjust this number based on observations when I brew.  For now, I am assuming 0.25 gallons.

Vferment = 5.25 gal.

• Add water lost to trub and hops in the boil kettle as well as transfer losses between boil kettle and fermenter.  I am guessing with the trub and hop losses with a value of 0.5 gallons.  My system tests showed that I lose about 0.25 gallons pumping from my kettles.  So total loss here is 0.75 gallons.

Vpostboil = 6.0 gal.

• Add adjustment for temperature shrinkage.  It seems water occupies a different volume at higher temperatures so we need to adjust for this.  I cannot claim that I totally understand this, but I am using (trusting) the value described in Ray Daniels book Designing Great Beers page 65: divide by 0.96.  Therefore, 6.0 / 0.96 brings us to a total of 6.25 gallons.
• Add the water lost in the boil (2.34 gallons) to the 6.25 gallons.

Vpreboil = 8.6 gal. = 8 gal. 2 1/2 qt.

• Add water lost in transfer from mash kettle to the boil kettle (0.25 gal from system measurements)
• Add water lost to grain absorption.  Here again, I put my trust in Ray Daniels and assume about 0.2 gallons per pound of grain gets absorbed: 0.2 gal/lb * 9.5 lb. = 1.9 gal.

Vtotal = 10.75 gal. = 10 gal. 3 qt.

I am using a total of 10.75 gallons of water, but I will mash with some smaller amount and sparge with the rest.  I use the fly-sparge technique.  If you batch sparge, then you will want to look into he optimal size for the number of runnings you perform.

When I mash, I will be using the ratio of 1.5 quarts per pound of grain:

1.5 qt/lb * 9.5 lb = 14.25 qt.

BUT, remember from my system measurements that I have a full gallon of water that sits below my false bottom in my mash kettle.  Therefore I need to add this amount (4 quarts) to my mash water: 14.25 qt + 4.0 qt = 18.25 qt.

Mash Water: 18.25 qt. = 4 gal. 2 qt.

Once I know my mash water amount, I simply subtract that from the total water to get my sparge water amount: 10.75 gal - 4.5 gal = 6.25 gal.

Sparge Water: 6.25 gal. = 6 gal. 1 qt.

So it is doubtful we have the exact amount of water, so to be safe I will actually make sure I have 7 gallons of water for my sparge - or perhaps place 12 gallons of total water in my HLT before removing the mash water amount (I initially place all water in my HLT so that I can use a campden tablet to remove the chloramine - but that is for a future post).

This should be a good first estimate.  Values will get tweaked as I gain a better insight during the brew process.  So this works great when you know the total amount of grains you are using.  What about when you are designing a recipe?  When calculating water, you need to know the amount of grain.  When creating a recipe, you need to know the amount of water.  How do you calculate the two together?  This will be addressed later.  First we will go through recipe formulation and then tie that together with calculating the water amounts.