Partial mash volume question

[OptimusJay]

I am planning my next batch to be a partial mash / partial boil recipe, due to my limitation of a 20qt brew pot.

My mash will consist of 9 total lbs of grains. So if I go with 1.5 quarts of water for each lb that means 13.5 quarts at the start of the mash. It would seem that I would not net that same 13.5 quarts due to what is soaked up by the grains. I will be using a DIY beverage cooler mash tun and plan to batch spare. Is there a calculation for measuring how much spare water to use? I want to make sure I don't end up with more than 4 gallons per-boil since my brew pot is only 5 gallons.

Thanks in advance,
Jay

 

[duboman]

Absorption is .12gallons per pound of grain

Take your strike water volume and deduct the absorption and that will give you the amount of first runnings you'll collect.

Then take your pre boil volume and subtract your first runnings to tell you the amount you need to use to sparge

 

[OptimusJay]

Hey, thanks for the absorption rate help.

I guess I was thinking that sparge volume was dependent on grain mash volume, not my boil volume. So will my combined runnings be "weak" due to the low volume of sparge water?

Jay

 

[duboman]

You'll get +\- 2 gallons first runnings and you'll sparge with +\- 2 gallons so you should be good

When you sparge, assuming batch sparging be sure to stir the heck out of the grain before you vorluef to really knock the sugars loose!

 

[OptimusJay]

Excellent, thanks much for the help/info.

Cheers,
Jay