Batch size and total Water needed.

I am new to this tool and there are something i do not understand with the bash size and Total water needed(Vols)

I have a 10g Boilmaker and are going to make 25 litres (6.60g). So i then set my batch size to 25 litre. and my equipment profile.
I have entered inn all the data:

Type: All Grain
Batch Size: 25.00 l
Boil Size: 30.96 l
Boil Time: 60 min
End of Boil Vol: 26.98 l
Final Bottling Vol: 23.11 l
Fermentation: Ale, Two Stage


Date: 12 Dec 2014
Brewer: CES
Asst Brewer:
Equipment: 10 Gallon BoilerMakerâ„¢ (5 gal/19 L)
Efficiency: 72.00 %
Est Mash Efficiency: 74.7 %
Taste Rating: 30.0

5.00 kg Viking Pale Ale (2-row) (6.0 EBC) Grain 1 95.2 %
0.25 kg Viking Crystal 100 (110.0 EBC) Grain 2 4.8 %
47.00 g East Kent Goldings (EKG) 2013 [5.00 %] - Boil 60.0 min Hop 3 25.3 IBUs
25.00 g East Kent Goldings (EKG) 2013 [5.00 %] - Boil 5.0 min Hop 4 2.7 IBUs
1.0 pkg London Ale Yeast (Wyeast Labs #1028) [124.21 ml] Yeast 5 -

Mash out data
Saccharification Add 34.66(9.140G) l of water at 70.3 C 66.7 C 75 min
Mash Out Heat to 75.6 C over 7 min 75.6 C 10 min


When i go the the "Vol" and see on "total water needed" it says 34.66 liters(9.14G)
This means i need to add 9.66 litres ( 2.55G) of water on top of the 25 liters.

Can this be correct sounds like allot?

I use a 10gallon MLT also, and those numbers align with mine.  Perhaps think of it as "using" water rather than "adding."

You are boiling off four liters (~31 down to ~27), and you would likely need 12-15 liters to sparge with, and some of that water would be left behind in the MLT. 

And your equipment may trap/lose some wort that cannot be transferred from the boiler to the fermentor. 

Review you Equipment Profile and start from the end of the process, and build in all the known losses along the way, and BSmith calculates the required starting point, the Boil Volume. 

Depends on where you have your losses set at.

I did an 11G batch size recently.

Total water needed 16.6 gallons

loss to grain absortion was 4.39 gallons.
cooling shrinkage 0.5 gallons
boil off 0.5 gallons
trub loss 0.3 gallons


So after losses my batch size is closer to 11 gallons needed.