For a single vessel system, the amount of strike water depends on a few variables:
● The batch size
● Trub loss
● The wort lost during the boil
● The liquid absorbed by the grain
It is best to work backwards from your final volume to figure out how much strike water is needed
Let’s say you want 11 gallons of wort in your fermenter. You expect to lose 1 gallon to trub and boil off 1 gallon. So at the start of the boil, you will need 13 gallons of wort.
Some wort will also be absorbed by the grains. During our Solo testing, we found that 0.5 quarts per 1.0 pound allowed us to hit our target volumes. 0.5 quarts per pound is a starting point and may have to be adjusted for the individual brewer. So if you have 20lbs of grain, you will lose 10 quarts or 2.5 gallons to grain absorption.
In this example the strike water needed is 13 gallons (pre boil volume) + 2.5 gallons (wort lost to grain absorption) = 15.5 gallons.
These numbers are just an example. After your first brew, it is important to record your losses and update your calculations for the next brew accordingly.
There are two types of brews that may require a different strike water calculation: half batches and big (high original gravity) beers.
For half batches, it is important to note that a large amount of the strike water will be under the basket and not in contact with the grains. Therefore, the strike water calculation above may result in not enough water contacting the grains. This will make the mash thick and limit sugar extraction resulting in lower original gravity than desired.
For an ideal mash thickness, the mash should have a 1 – 1.5 quarts of water per pound of grain ratio. The water in this ratio is only the water that is in contact with the grains and does not include the water outside of the basket (also known as “dead space”). If your ratio is under 1 qt/lb, it may help to add more strike water.
You are doing a 5 gallon batch in a 20 gal Solo with 14 lbs of grain.
You want 5.5 gallons into your fermenter. Expected trub loss and boil off are 0.5 and 1 gallon respectively. The grains will absorb 7 quarts of water (1.75 gal).
So your original strike water calculation is 5.5 + 0.5 + 1 + 1.75 = 8.75 gallons
Then you need to determine how much of that will be “in” the basket and in contact with the grains. Do this by looking up 8.75 gallons in the first column Table 3 HERE. The second column tells you there are 12.48 quarts in the basket.
This results in a ratio of 12.48 quarts / 14 lbs of grain = 0.89. Since that is under 1, the mash will be very thick.
In this example, you will want 14 quarts of water in the basket to get a ratio of 1 qt/lb. Looking at 14 quarts in the second column, it corresponds to 9.25 gallons of strike water.
So it is best to start with 9.25 gallons of water for this batch. To end up with the same volume of wort into the fermenter, either keep the output of the heating element between 90-100% during the boil or do a longer boil.
Big beers (high original gravity)
When making big beers, it is important to note that the initial strike water calculation may result in more water than can fit in the kettle with all the grains. In these cases, we recommend adding less strike water then add more water after the mash.
You want to brew a big beer with 40 lbs of grain in a 10 gal batch.
Our initial strike water calculation is:
11 gal (into fermenter) + 1 gal (trub loss) + 1 gal (boil off) + 5 gallons (grain absorption of 0.5 qt / lb) = 18 gallons.
However, 18 gallons of strike water + the volume of the grains will not fit in the 20 gal kettle. We do not recommend using more than 16.5 gallons of strike water.
So in this example we recommend using 16.5 gallons of water during the mash. After the mash is completed, you can pour 1.5 gallons of 170F water into the basket while it is hanging on the kettle. This will ensure you reach your batch size and also act like a sparge to help rinse more sugar off the grains.
In this example, the ratio of water to grains in the basket will be thick, under 1. However, the additional water added over the grains will help increase the efficiency.