Not enough sparge water?

[greenleaf586]

I'll be brewing an Imperial Stout tommorow and was putting my schedule together. After entering my amounts into the brew365 calculator, its only calling for 2.2 gallons of sparge water for a 20.4 lb. grain bill. This seems extremely low to me. Any thoughts?



Batch size (gal.) 5.5
Grain Bill (lbs.) 20.4
Boil Time (hrs.) 1
Trub Loss (gal.) .5
Equipment Loss (gal.) .25
Mash Thickness (qts/lb.) 1.5
Grain Temperature (deg.) 65
Target Mash Temperature (deg.) 153


Constants
Wort Shrinkage (pct) 4
Grain Absorption Constant (gal/lb) .13
Percent Boiloff per Hour (pct/hr) 10


Results
Total Water Needed (gal.) 9.85
Mash Water Needed (gal.) 7.65
Sparge Water Needed (gal.) 2.2
Strike Temperature (deg.) 164.73

 

[dankev]

Mashing 20.4 lbs at 1.5 qts/lb means your mash of 7.65 gal will give you 5.1 gallons into the kettle. Sparging with 2.2 gallons brings you up to 7.3 gallons in the kettle. If you want to sparge with more water, you'll need to boil longer to get the water volume back down.

 

[greenleaf586]

I guess my question is how can 2.2 gallons of water be enough to rinse that amount of grain? I plan to batch sparge, draining the mash tun, then adding sparge water (all 2.2 gallons!). Will this 1 sparge step be enough to get me a decent efficiency? Thanks!

 

[Hammy71]

Probably not. That's why dankev said you'll have to boil longer. For the RIS I brew, I have a 2.5 hour boil. That way I can sparge with the proper amount of water. You'll end up with more wort than you can boil off in an hour, hence the longer boil. Once you've boiled down to your normal pre-boil volume you can brew as normal (hop additions, chilling, etc.). Hope that makes sense.....