Trying to get the right amount of sparge water

[LuNchBoX1371]

So i am using brewsmith and it keeps telling me that i need to sparge with 1.9 gallons of water. My recipie is a 2.5 gallon batch with no top off water, and my boil off is 1.2 gallons per hour; so i wanted to end with 3.7 after my mash is done and fly sparging is done. Now my problem is that brewsmith just keeps telling me to mash with 14.5 quarts of water and fly-sparge with 1.9 which will give me 5.2 gallons or something like that which is not what i had put dont as my est. pre-boil volume. Can anyone help?

 

[lump42]

It sounds like you are forgetting about the the volume loss to grain absorption and mash tun dead space.

Taken from BYO article "Calculating Water Usage: Advanced Brewing", Issue: November 2006
https://byo.com/stories/item/410-calculating-water-usage-advanced-brewing

Total volume of sparge water = Target pre-boil volume - volume of first runnings
Volume of first runnings = Strike water volume + volume of any other water added to the mash - volume of water absorbed by the grain - volume of liquid remaining in the bottom of the mash tun - volume of liquid remaining in lines or pump

BYO suggested using 0.5L per lbs of grain as an average value for grain absorption

 

[LuNchBoX1371]

i dont see a space to change the grain absorption?

 

[botigol]

It is on the Advanced tab under Options.

 

[LuNchBoX1371]

Thank you so much; today is bre day with- like i said- my first all-grain day and wanted to get it right. Thank you again