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Water Volume Management in All Grain Brewing

Saturday, June 12th, 2010

How to hit your target wort volume spot on.

There are several factors that go into how much water is lost during the brewing process from mash to fermentor.

1) Grain Absorption: Figure 1/2 quart per pound of grain. This comes out to ~1 pint (0.125 gallons) / pound of grain. Some reports are as high as 0.2 gallons per pound.

During the mash process the grains soak up water. This water is not transfered to the kettle when lautering. Make sure if you do a high gravity batch to account for this. My last big batch was a little short on wort volume and grain absorption is exactly why.

2) Mash Tun Dead Space: Dead space varies by equipment. Some of the water / sweet wort is left behind because of the shape of the mash tun or location of the valve.

I estimate 2 quarts (0.5 gallon) in my cooler mash tun.

mash tun dead space

3) Boil Off / Evaporation Rate: This depends on how vigorous of a boil and the shape of the kettle. The average is around 1.5 gallons (6 quarts) per hour. If the kettle is narrow (like a keggle), expect ~1 gallon per hour, or short and wide, as high as ~2.5 gallons / hour. If you are brewing with Pilsner malt and want to do a 90 minute boil to drive off DMS (which I do on my lagers), make sure to account for the extra boil time.

brewing boil off

4) Trub loss: Water absorbed by hops or adjuncts. I estimate 1/2 quart (0.125 gallons).

5) Wort Shrinkage: When the wort cools it looses some volume (4% is standard). This is minor in a 5 gallon batch, about 0.8 qt in a 5 gallon batch, and 1.6 qt in a 10 gallon batch.

Example Calculation 1:
How much starting water is needed to make a 5 gallon batch given, a) 10 pounds of grain, b) 60 minute boil? I shoot for 5.5 gallons of wort, to allow for samples, losses in the fermentor and bottling bucket. It is easier to work in quarts for water volume measurements.

5.5 gallons wort = 22 quarts
Grain losses = 5 qt (10 pounds * 0.5 qt/pound)
Dead Space = 2 qt
Boil off = 6 qt (1.5 gallons/ hr)
Trub loss = 0.5 qt
Shrinkage = 0.8 qt

Total input water: 36.3 quarts, or 9.08 gallons.

Example Calculation 2:
How much starting water is needed to make a 10 gallon batch given, a) 25 pounds of grain, b) 90 minute boil? Let’s go for 11 gallons total.

11 gallons wort = 44 quarts
Grain losses = 12.5 qt (25 pounds * 0.5 qt/pound)
Dead Space = 2 qt
Boil off = 9 qt (1.5 gallons/ hr)
Trub loss = 0.5 qt
Shrinkage = 1.6 qt

Total input water: 69.6 quarts, or 17.4 gallons.

Figure out your mash tun dead space and your boil off rate, and you will be able to hit your target volume spot on every time!

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  1. 10 Responses to “Water Volume Management in All Grain Brewing”

  2. What is the risk of over estimating and just keep sparging until you have a target boil size? IE have some left over sweet wort in the mash?

    Is it best to drain the mash as much as possible?

    By Peter Baker on Jun 25, 2010

  3. PS Thanks for the awesome article!

    By Peter Baker on Jun 25, 2010

  4. A repeatable process is the key to success in home brewing.

    My 15 gallon kettle does not have a sight gauge, making it difficult to tell the volume. This forces me to carefully measure the water going into the mash tun. My 20 quart starter kettle (used during extract brewing days) is perfect for kicking off a batch of all grain. Given the procedure above, I have never needed to add a sight gauge to my kettle, but it would be cool.

    I drain the mash as much as possible in all my batches to maximize brew house efficiency. I do this consistently so that each time, I know where I am at. I live with the 2 quarts of dead space. Leaving behind more than that, I would feel bad.

    Leaving behind a random or unknown amount of wort would lead to variations in alcohol level, flavor, and bitterness. If you are sparging in a consistent manner, and know what your brew house efficiency is, I don’t see a huge problem with it. It is technically wasting a buck or two of grains. By diluting the mash with sparge water, and leaving some of the sugars behind, you will start with a lower gravity wort in the kettle. That means either: a) longer boil to get the same original gravity and less wort going into the fermentor, or b) lower original gravity thus lower alcohol content in the beer.

    By the way, sparging can lower the pH of the mash, that might also factor in.

    By Larry on Jun 25, 2010

  5. So where in your mash process do you add the extra water to account for losses? In the strike water or the sparge water or both?

    By Joe on Sep 7, 2010

  6. I add the extra water to the sparge because I want my strike water to give the correct mash thickness (say 1.5 qt / lb of grain).

    By Larry on Sep 9, 2010

  7. How much evaporation is there when heating the strike water?

    By Mark P on Jan 30, 2011

  8. I notice very little evaporation when I’m heating the water. It doesn’t get close to boiling temps.

    By Larry on Jan 30, 2011

  9. How long do you let the sparge water sit on the grain before runnoff?

    By Gary on Apr 17, 2011

  10. > How long do you let the sparge water sit on the grain before runnoff?

    60-90 minutes during the mash, then 20-30 minutes for the sparge depending. Longer is better for efficiency.

    By Larry on Apr 17, 2011

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