Queston about DeathBrewer's Partial Mash System

Hello,

This is my first post here, I've been lurking for a couple of weeks and have soaked up quite a bit of useful information. I've brewed three extrect batches thus far, and now wish to try DeathBrewer's partial mash system involving a large grain bag.

Here's my question: I understand that I will want to mash with about 1.25-1.50 quarts per pound of grain, but how do I determine the amount of sparge water needed? I've read through much of the sticky thread, but this part is still not clicking for me. Will I get lower conversion with different amounts, or do I measure the sparge amount based on the total water need for the boil. Am I overthinking this?

I'll be doing a three gallon batch with 3.5 lbs of grain.

Thanks

The amount of sparge water is just whatever amount you need to get to your target pre-boil volume.

Plan on 1.25-1.5 qts per lb of grain.

Assume you will lose 0.1 gallons per pound of grain to absorption.

Determine what pre-boil volume you need.

Do the math.

Example:

I want 5.5 gallons in my fermenter. I need to boil 7.25 gallons of wort to hit 5.5 gallons in the end. I am using 10 lbs of grain.

10 lbs of grain * 1.5 qts/lb = 15 qts of water = 3.75 gallons strike water (for mash)
10 lbs of grain * 0.1 gallons/lb absorption = 1 gallon of water absorbed by grain during mash
Wort from mash = 3.75 gallons - 1 gallon = 2.75 gallons from mash.

I want 7.25 gallons in the kettle for the boil, so 7.25 gallons - 2.75 gallons = 4.5 gallons. I need 4.5 gallons of sparge water.


Edit, duh, just saw your numbers:
3.5 lbs grain * 1.5 qts/lb = 5.25 qts or 1.31 gallons to mash
Absorption loses you around .4 gallons
You collect 0.9 gallons of runnings
you want 3 gallons in the end
Call it 4 gallons pre-boil, (to account for evaporation)
You need 4-0.9=3.1 gallons sparge water. (Unless you are adding LME, in which case subtract the LME volume from the sparge water).

Beersmith is awesome for this stuff...it's all done automatically for you.

My stove is too small to do a full boil in a 6 or 7 gallon pot so I have to do partial boils. I've used DBs method many times with great success! For sparging, I definitely don't use 1.5 qts/lb. I simply take the largest pot I have, figure out how much water I can get in there with the grain and go with it. It's not perfect and I probably lose a bit of efficiency but it still makes great beer!

I've used this method with a lot of success, and FWIW I always got better efficiency with a thinner mash (1.5 qts/lb). Use the above posters' suggestions re: sparging to get enough water to boil.

This can turn into a little bit of a problem if you're doing full boils and mashing less than 6-7 lbs of grain. A good rule to follow is to not use more than 4qts (1 gallon) per lb of grain of water total (by "total" I mean mash+sparge). This way you'll avoid oversparging. So, basically, if you're doing a full boil and mashing 5 lbs of grain, you can mash at 1.5qts/lb, which will leave you with about 1.25 gallons for your first runnings (1.5*5=7.5 qts - 2.5 qts absorbed=1.25 gallons). Then sparge in the remaining 12.5 qts (2.5*5). Then add whatever additional water you need to make your pre-boil amount.

I hope that wasn't too confusing!

Thanks for the replies (and thanks to shorty for running the numbers for me). I guess it is neary as simple as it seemed. It looks like I'll need to look into Beersmith for my brewing calculations.