Originally Posted by EricScott
I would like to try this. How do you know how much mash and sparge water to use? Thanks!
Basically, you have to work backwards: You want at least 5 gallons of wort. Usually, I shoot for about 5.5 gallons. Your grains will absorb about a gallon per 10lbs, give or take a bit. BUT, they only absorb water on the mash, on the sparge they're still full of water from the mash.
Figure about .15 gallons per pound of grain, or use about a pint per pound. It'll all work out and you can drink you mistakes. So, ADD that amount to the 5.5 gallons of wort you want. Say you have a 7.5lb grain bill, you add 7.5 pints (or almost 4 quarts- a gallon) to your 5.5 gallons desired. So, you're up to about 6.5 gallons of water.
Now, you have to add your boil off amount. I can't tell you what yours is, you have to do a boil to find your actual number. But, you can guess the first time. I did. Anyway, I add about another 1/2 gallon for boil off. I have a tall narrow pot. For a wide, fat pot, I'd add more. Now, I'm up to about 7 gallons.
Seven gallons does not fit comfortably into my 7.5 gallon pot that really only holds about 6.75 gallons to the rim. So, I split this into two pots. Sixteen quarts in one, and eight and a half quarts into the other.
I heat the larger amount first, and use that to mash. While that mash is going on, I heat the smaller amount. When mash is done, sparge in smaller amount. Simple, done, drink more beer.