I slowed down my sparge on 12 gallons of Belgian Singel, and ended up with 1.058 instead of 1.050. Not a huge increase in efficiency, but a big enough spike to notice it 
Here is a study conducted by CRAFT on the poor effeciency we were getting with our keggle system. It agrees with your findings
http://beerdujour.com/pico-efficiency.html
Fred
And if you were just batch sparging, it wouldn’t matter! 
At least, in the dozen or so trials I’ve done, that’s what I found.
You know Denny, as much as I love and do fly/continious sparging I now reserve that process only for those beers I make with a mashtun FULL of grain (26-30 pounds). Otherwise even I batch sparge, though slightly differently than you do. (after running to clear) I first drain the mash tun (no additional water), then add half the remaining volume I need, and finally the other half. That way I don’t need to worry about how much I’m going to get out of my mash tun. I ‘know’ I’m doing something wrong because I use a 10 gal YELLOW round cooler.
Distracted, in the study we did NOT look into batch sparging.
Fred
Fred, what’s the reason for doing 2 sparge additions? Not enough room in the cooler to do it all at once? That’s the only time I find myself doing more than one.
I never considered the first initial draining as a sparge and did two (I guess I can’t count) sparges following that. I’ll try one sparge next time, I guess it’s my lame fly sparge mentality. These batch sparges are mostly for my “starters” so low gravity is not an issue.
Fred
There seems to be a lot of confusion over what constitutes a “sparge”. In my world, I run off the mash. I may have added water to the mash before that runoff, but I consider that a mash addition, and not a sparge addition. Then, after the tun is drained, I add what I consider my sparge water. I do that only that one time unless I’m using so much grain that I can’t get enough water in. In that case, after that first “sparge” is drained, I add more water and drain again. But I seldom need to do that. There are some who will take the single sparge addition I do and divide it in half and add “sparge” water twice. I’ve found so little benefit in doing that that it’s not worth the minimal time or effort it takes, as far as I’m concerned.
I often try to avoid this confusion by referring to “two run-offs” instead.
Slow sparging gives you better efficiency because the grain bed is rinsed more evenly. If you run off to fast, the wort and water are more likely to look for the path(s) of least resistance.
Kai
So Fred, the gist of what I am reading says your research indicated that the best flow rate for sparging was between .08 and .3 gallons per minute.
Playing around with the numbers tells me that for my 14 gallon boil on a 12 gallon batch I need to sparge at a rate that takes ~74 minutes to fill my kettle. And for a 6 gallon batch boiling 7.75 gallons I would need to sparge for ~41 minutes. These times are based on the mean of 0.08 and 0.3 which is 0.19 GPM flow rate as a starting point.
I do not see any mention in this line of thought for taking into account the amount of grain in the mash other than the volume of the boil. I wonder how this would hold up taking a same batch size of say a Mild Ale and a Barleywine and lautering at the same rate to see if the efficiency was the same or not. Too bad I am not the scientific type 
That about covers it. Your system could have a different response than CRAFTs. At the time I did that I was not familar with batch sparging. Batch sparging here seems to make sense unless you don’t have the volume for it.
Fred
Fred, great research. It actually agrees with the numbers I’ve been getting on my cooler tuns.
BTW:
For 1.100 I repeatedly get 55%
For 1.110 I repeatedly get 44%.
Both at a 1.25 ratio, because that’s as low as I want to go.
Just one small bone to pick on charting practices.
The Independent axis is the X or horizontal.
The Dependent axis is the Y or vertical.
General practice also dictates the origin (juncture of X and Y axis) to be the lowest value, which you have done.
You are plugging in gravity ( independent, or chosen variable) and charting the efficiency found ( dependent or the result of experimentation) hence the axes are reversed in the posting.
It just makes understanding you excellent work easier.
unless we are talking economics ;D
Since my life sucks, I have calculated the above referenced sparge collection rates into Milliliters per minute. These rates should be the handiest for setting your sparge flow, but by dividing the numbers by (2) you can get a 30 second rate in milliliters.
Collection Rate Range: Low Mean High
Milliliters per Minute: 303 720 1,137
I don’t care about what everyone says, fly sparging has gotten me higher points all the time. What it really boils down to is TIME. When I FS, it takes 1 hr. BS takes about 20 min. The point differential is small.
According to the above information on 12 gallon final volume batches I need to take 80 minutes to fly sparge to hit the average flow rate from the chart. I do not mind the extra time fly sparging takes because I can clean & sanitize a lot of fermenter/kegs and rack a lot of beer in 80 minutes. I have a very busy brewery, so I never find myself just sitting around watching/waiting on a sparge…YMMV
One thing I’ve noticed batch sparging is that when I slow down the runoff it gets clear. When I speed it up it gets cloudy.
I usually let it go fast and have the paricles settle out after the boil.
I haven’t experimented yet to see if there is an effect on efficiency or flavor of the finished beer. Would be interesting though.
Back when I use to batch sparge I did it the Denny way and drained the mash-tun as fast as I could, but the wort was clear. What are you using as a filter?
Bo - 50 to 58 IS pretty significant. Of course consistency matters more than efficiency, but let’s say that 12 gallon batch was 22 lb of grain for your normal 1.050. That would be ~75% efficiency. Move it up to 1.058 and you now are ~87%. I’d call a 12% increase substantial!
I’ve never found a really long sparge to be useful. My MO is kinda a batch sparge saddled onto a fly. After mashout and vorlauf I runoff the tun till I see the grainbed, then I slow the flow slightly and start fly sparging. Generally I add water at mashout and probably remove 1/3 of the boil volume with the initial draining of the tun.
stout - I haven’t made a really big beer in quite some time but my notes show a 70% efficiency on a 1.125 Scottish 140/- and 65%+ on a 1.102 Bigfoot Clone. You may want to crush finer, 44% and 55% sound really low.
FWIW - I got 64% on a no-sparge (single draining of the tun) 1.054 ESB.
I start out slow. After a qt. or so it clears up and then I go full out.
As far as I’ve been able to tell after 350+ batches, cloudy runoff has no effect on the flavor or appearance of the finished beer.
Include me in the FS camp as well… I usually sparge for a bit over an hour. Longer has always gotten me better numbers. Likewise I have plenty to do on brew day during the sparge. And after all, it is a brew DAY! 