Originally Posted by CaptKiRkLeS
This brings up another question about the amount of water needed...Say I use the calculated mash and sparge but I run short on my pre-boil volume, do I add more sparge water to my MLT? Could I just add extra water to the initial sparge water and stop once I hit my pre-boil or would I just be losing efficency?
Adding more water than you need is going to reduce your efficiency unless you increase your boil to compensate.
You have a set amount of sugars in your grain that you are going to get out during the sparge.
Lets say you want 7.5 gallons total volume, and you have 4.5 from your mash.
If you use the correct amount of sparge water, 3 gallons assume you get runnings at 1.040 gravity. If you used 3.5 gallons under the same conditions then you would get your runnings at (1.04*3=C*3.5) 1.034 which would lower the total gravity of your boil, and thus the gravity going into the fermenter UNLESS you boiled off that extra half gallon.
I always heat up more sparge water than I think that I'll need, but I'm sure to measure the first runnings of the mash so that I can get an accurate pre-boil volume before I start sparging. If you run short, then you can just do a small second sparge.