False Bottom / mash volume question

[binabik]

I just got my 10 GAL BK with a false bottom. The false bottom site at about
the 2 GAL mark. If I was using 1.5 qt / lb of grain, do I need to add an additional 2 GAL/ 8 qt to my initial volume since the majority of the grains
should be above the false bottom?

Thanks

 

[Black Island Brewer]

In short, yes. So 10 pounds of grain would be 15 quarts plus 8 quarts for the dead space. If you're using BeerSmith, you can add it to your equipment profile under Lauter Deadspace and it will add it for you after you put in your water to grist ratio.

 

[Qcbrew]

In short yes. If you want to be super precise you could make a brew by assuming the dead volume (or lauter deadspace whatever it's called in the program you are using) as 2 gal. When you sparge calculate how much you are supposed to get vs how much you actually got.

What I mean by this; say you have 10 lbs of grain

You want to add 15 qt of water + 8 for the dead space=23 qt
The grain will absorb some of the water (about 0.527 qt/lb) which means you will loose about 5.3 qt to your grain.

You should then drain 23qt-5.3qt-8qt=9.7 qt (or about 10 if you like round numbers).

Say that instead of that you get 12 qt of liquid. Your dead volume was actually 6 qt so you can add 2 qt less to your sparge volume to reach your pre-boil volume so you hit your expected batch volume.

Basically, you are right if you have 8 qt of dead volume you have to add it to your strike water. What I'm saying is that it can be hard to guess your dead volume, so it's best to calculate it experimentally. This is just for higher precision.

 

[binabik]

Thanks. That's what I expected.