Fly Sparge adjustment questions

I am gong to do another fly sparge and am trying to figure this out.
If I have 10 lbs of grain and mash @ 1.25 quarts per lb
that's 3.125 gallons for the mash
I've read that you can estimate sparge volume at twice the mash volume
so that's 6.25 gallons of sparge water
I've also read you want to sparge @ 1 quart per minute
6.25 gallons = 25 quarts
so is my sparge done in 25 minutes ?
Or do I slow down the rate to .5 quarts per minute so the sparge takes longer?
Or do I lower the mash volume to increase the sparge volume to allow for longer sparge?
Or any and or all of the above?

You can use anything from1 - 2 quarts per lb for the mash. 1.25 quarts per lb is a good starting point.
Rather than estimating the amount of sparge water as a multiple of the mash water volume, I would calculate it from the required pre-boil volume.
During the mash, the grain will absorb about 1 pint per lb, leaving 0.75 quarts per lb of mash water that will be released during the sparge.
I need to collect 7 gal wort pre-boil. This gets boiled down to 6 gal in 60 minutes, and I lose another 0.5 gal to dead space, hop absorption, and trub when transferring to the fermenter. Your figures may vary a bit from mine.
So I need to collect 7 gal (28 quarts).
With a 10 lb grain bill, I can get 7.5 quarts from the mash water (assuming no dead space in the MLT) so I need to use 20.5 quarts of sparge water to collect the full 7 gal. Unfortunately, my MLT and HLT each have about 4 quarts of dead space, so I need to prepare an extra 8 quarts to account for the dead space. i.e. I would need 28.5 quarts sparge water.
With my 5g MLT, I can sparge 10 lbs grain in about 45 minutes. (That's 28 quarts in 45 minutes. Much slower than Palmer recommends)
With the 10g MLT, I can sparge 10 lbs grain in less that 1/2 hour (slightly faster than Palmer recommends). I believe that this is because the 10g MLT has a larger collection area, allowing faster collection without excessive channeling.
I would start with a slow sparge, and then see if you lose any efficiency with a faster sparge. If you do lose efficiency, is the cost of extra grain worth the time savings? If you don't lose efficiency, don't waste time sparging more slowly than necessary.
The other thing that has to be taken into consideration is the possibility of oversparging. You want to stop the sparge before the gravity of the runnings drops below about 1.010 (A refractometer is ideal for checking this.) If I fly sparge with 10 lbs grain, I find that the gravity of the runnings drops below 1.010 before I have collected the required volume. In this case, I just make up the volume with water.

Hope this helps.

-a.

dzlater said:

so is my sparge done in 25 minutes ?

Click to expand...

That's awfully quick for a fly sparge. Best rule of thumb I try to follow is 1 gallon every 10 minutes:traditional fly sparge times are 60-90 mins. You have to go pretty slow to get tannins.