I'm getting an extra gallon of sparge runoff?

I have a bizarre problem. I recently moved and just now got my brewery up and running. For my first two batches I am somehow ending up with almost a full gallon extra runoff after the sparge. The only thing that has changed is my the water I am using and Midwest Supplies has a new grain mill setup. Other than that, nothing has changed. Can the crush somehow affect water absorption by the grain? Can water chemistry somehow have an affect on this problem? I'm stumped.

I mash at about 1.3 qt/lb in a Colemen Extreme 36 qt cooler.

That's weird... I might be inclined to think that if the grains are not all crushed very well, they may not absorb as much water.
I really can't see water chemistry affecting absorption to any significant degree.

Are you measuring your first runnings and calculating your sparge volume based on that number?

My measurements haven't changed. I've always assumed the same grain absorption, I then use that number to get my mash out water for the first runnings. The mash water, minus absorption, plus mash out water should equal half of the total wort I want to collect. The water for the second runnings has always been half of the total I want to collect.

I could let the problem go if it were an extra quart, but I'm getting over a gallon extra! It doesn't make sense.

It sounds to me like your maths are off somewhere. For your next batch, measure the water in every stage, from mash to boil. Don't assume the grainbed absorption, calculate what it is! Measure the water in to the mash, then out again and that should tell you what the actual absorption rate is.

Don't just rely on theoretical values of absorption (i.e. .10-.12 gallons/lb of grain); there are too many variables that could skew one way or another.

Just measure the volume of your first runnings and calculate your sparge volume based on that real-world number to hit your target volume.

flyangler18 said:

Don't just rely on theoretical values of absorption (i.e. .10-.12 gallons/lb of grain); there are too many variables that could skew one way or another.

Just measure the volume of your first runnings and calculate your sparge volume based on that real-world number to hit your target volume.

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Yeah, I know I could do that but they always say you get better efficiency if the first and second runnings are equal.....

goswell said:

Yeah, I know I could do that but they always say you get better efficiency if the first and second runnings are equal.....

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I say you'll notice an increase in efficiency by matching the volumes of the second and third runnings.

If you are targeting 8 gallons pre-boil, and get 2 gallons from the first runnings then your sparge volume should be 6 gallons, split into two 3 gallon volumes.

Has your efficiency changed?

this is the main reason why I will be fly sparging.

MilwaukeeBrewGuy said:

this is the main reason why I will be fly sparging.

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How so? For an increase in lautering efficiency?

well no that is not the primary reason, but surely a benefit. I was under the impression that I wouldn't really need to calculate the amount of water needed with fly sparging. Can't you simply fly sparge until you hit your desired pre-boil level? Maybe I am missing something here?

Your grain should only absorb about a gallon.... a little more... but for you to to get another GALLON, youd have to basically have UNCRUSHED grain. It is a math problem.

I fly sparge, but I can run my HLT and MLT dry during the sparge and hit my pre-boil and post-boil spot on...

MilwaukeeBrewGuy said:

well no that is not the primary reason, but surely a benefit. I was under the impression that I wouldn't really need to calculate the amount of water needed with fly sparging. Can't you simply fly sparge until you hit your desired pre-boil level? Maybe I am missing something here?

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Thats the way I do it, although I have only done 5 all grain batches.