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Water absorption
I was wondering how much water typically gets absorbed by the grain during the mash. I have been taught to expect 1/2 qt per pound and I have seen some calculations say as little as .1 gallon per pound. It always seems like I am coming up short. I expect there to be some variance depending on the system, but it looks like I lost just over 2 gallons with 10 pounds of grain today.
I mashed in with 12.5 qts and prepared 22 qts of sparge water. When all was said and done, I still had to add 2 qts of water to get a pre boil level of 7gallons. ( -2.125 gallons)
How much does everyone else calculate for??
First question is if you fill your mash tun with just water and drain it, how much water do you leave behind? You could easily have a manifold set up that is leaving half to one gallon of water regardless of mash absorbtion.
I assume you are batch sparging as fly sparging this is a non-issue really.
I usually assume about 10% volume loss to grain absorbtion. So in a 5 gallon mash (20 quarts) I would expect to have 2 quarts absorbed by the grain.
That's a good point. There is probably some amount of water that could be left behind regardless of whether or not there is any grain. I will do a little experiment to see how much that is.
I'm not sure why the type of sparge would make any difference though, the grain will still absorb some amount of water no matter which I use. I have been fly sparging with what seemed like enough water (calculating that the grain would absorb .5 qts per pound) and coming up short of the 7 gallons I want for boil.
I guess as long as I know what my system typically does, I can calculate from there. I am curious what others see as well. Thanks for the advice.
brewchez wrote:
I usually assume about 10% volume loss to grain absorbtion. So in a 5 gallon mash (20 quarts) I would expect to have 2 quarts absorbed by the grain.
So with 20 qts of water, I would assume you are using somewhere between 15 and 20 pounds of grain? and you only see a 2 qts loss?
SliDillon wrote:
I'm not sure why the type of sparge would make any difference though
I think the point is that while fly sparging you are contimually adding water until you are done, so actual volume dosn't even matter.
What a lot of batch spargers (you know who I am talking about -LOL) forget is that we still need to prepare A volume of water for our sparge,there is not just some endless source of 180 deg conditioned water.
I usually use a thin mash when possible (1.5qts / lb) and to get my 14.5 gallon runoff I have to sparge with 10 gallons, then drain the tun from the mash. If it is a big beer, I usually have enough in the tun to reach full runoff volume. Sometimes a smaller beer will have less in the mash so I have to get another few gallons at the ready to sparge if it looks like I will come up short. Luckily I have a sight tube on my mash tun, so I know approx what level of water I have left in the tun.
Don't know if any of that helps you, but my advice would just be to have some extra sparge water handy JIC.
thirsty wrote:
What a lot of batch spargers (you know who I am talking about -LOL) forget is that we still need to prepare A volume of water for our sparge,there is not just some endless source of 180 deg conditioned water.
What?? You don't have a leprechaun type creature that emerges from the wall with a 180d water hose for your fly sparging?... 
thirsty wrote:
I think the point is that while fly sparging you are contimually adding water until you are done, so actual volume dosn't even matter.
BINGO!
thirsty wrote:
What a lot of batch spargers (you know who I am talking about -LOL) forget is that we still need to prepare A volume of water for our sparge,there is not just some endless source of 180 deg conditioned water.
I can see the point now actually of how the amount of absorption is important to fly spargers. You have to account for the loss just like we batch guys do too.
SliDillon wrote:
brewchez wrote:
I usually assume about 10% volume loss to grain absorbtion. So in a 5 gallon mash (20 quarts) I would expect to have 2 quarts absorbed by the grain.
So with 20 qts of water, I would assume you are using somewhere between 15 and 20 pounds of grain? and you only see a 2 qts loss?
That sounds about right.
Its jsut an estimate and it will vary brewer to brewer based upon the extent of the crush and the water basis of your grains, and your local humidity.
brewchez wrote:
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I can see the point now actually of how the amount of absorption is important to fly spargers. You have to account for the loss just like we batch guys do too.
Yeah, that's what was throwing me off. I prepared what I thought was more than I needed, only to come up 2 qts short.
I feel like I have a better idea of what my loss should be now, so I hope to have the right amount of sparge water ready next batch.....I may have to get another pot though 
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