# Water Displacement

I’m toying with the idea of going BIAB and am trying to figure out how big of a kettle I’ll need for both 5 and 10 gal batches using a no sparge BIAB method.

I have seen the following formula…

Total water volume = final batch size + trub/hop loss + boil off loss + grain absorption

But the one thing I feel like it doesn’t address is the amount of water displaced by your grain. In other words, when I put a bunch of grain in a pot with water, the water level will be pushed higher as a result. Is the simple answer that the displacement is offset by the water absorbed by the grain?

Appreciate any help.

[quote=“Chris-P”]I’m toying with the idea of going BIAB and am trying to figure out how big of a kettle I’ll need for both 5 and 10 gal batches using a no sparge BIAB method.

I have seen the following formula…

Total water volume = final batch size + trub/hop loss + boil off loss + grain absorption

But the one thing I feel like it doesn’t address is the amount of water displaced by your grain. In other words, when I put a bunch of grain in a pot with water, the water level will be pushed higher as a result. Is the simple answer that the displacement is offset by the water absorbed by the grain?

Appreciate any help.[/quote]
I can tell you from a smaller BIAB that you’re right about that formula not accounting for displacement. That formula is for figuring out how much water you need; it’s not for figuring out pot size. Sorry, I don’t have better insight.

I had read a 10 gallon pot is the minimum size for a 5 gallon batch of beer.
Estimate 10 fluid ounces for each pound of grain. This is from Palmers chapter on all grain brewing in his online book.

I’ve never brewed using the BIAB technique, but I’m guessing the Can I Mash It?

calculator found on this page could be useful in determining the minimum kettle volume required for a particular recipe.

[quote=“Dan S”]I’ve never brewed using the BIAB technique, but I’m guessing the Can I Mash It?

calculator found on this page could be useful in determining the minimum kettle volume required for a particular recipe.[/quote]

Yeah, so I was thinking that you could reverse engineer the equation a bit…

Take the total pre boil volume you think you need. For 6 gallons in the fermenter, I want a pre boil volume of 7 gallons (28 quarts).

Let’s say i have 10 lbs of grain in my recipe. That’s 2.8 quarts per pound of grain (28/10)

Go to the Green Bay Rackers Can I Mash it and Plug in…

Weight of Grains: 10 lbs
Quarts per Lb: 2.8

You get “This mash will take up 7.8 gallons of space”

This seems to work, but I’d like to have a bit more insight into how the rackers calculation comes factors in displacement.

So 10 lbs. of grain (absorbtion included, I assume) will only displace 0.8 gal. of water.

Good to know.

The “can I mash it” calculator is the way to go. I have had several sizes of kettles, from 4gal all the way up to 25gal, and I’ve BIAB’ed in all of them. I’ve found that any kettle that you can boil in without a boilover is sufficient for that volume of BIAB for an average gravity beer. For example, I can do an all grain batch in as small a kettle as 8.5 gallons; BIAB in that kettle will be just to the rim with 14# of grain, which gives an OG of about 1.070.

I do 3-5 gallon BIAB. I use a 7 gallon kettle for my 3 gallon brews and a 15 gallon kettle for my 5 gallon.

I use this calculator to figure how water I will need when I dough in. I have found it to be very useful.

http://www.simplebiabcalculator.com/