For the few years I've been brewing AG, I've used batch sparging with a 70qt cooler. But this year I've built a new brewery which is equipped for fly sparging, so I'm trying that.
With fly sparging, I understand sparing should be stopped when the SG below 1.010 (or the pH above 5.8). But With the lauter tun full of 1.010 wort at the end of sparging, doesn't that hurt efficiency compared to other forms of sparging?
The sugars left behind in a batch sparging scenario are generally the same as in a fly sparge set up. The only difference is that in batch sparging there is no water left in the tun. In fly sparging the tun is filled with water. But the net effect on efficiency is the same. If you were to go and fill the batch sparged tun up again, as if to do a third run off, it would be at or around 1.010. You can't get all the sugars out regardless of method being used. 100% efficiency does not make the best beer either.
So no, its not hurting efficiency over other forms of sparging.
Ideally, your flow rate into your mash tun would be at or less than your flow rate through the mash and out into your kettle. In this case, liquid shouldn't be collecting in your mash tun, and when you hit 1.010 SG in your kettle you can simply stop adding sparge water. The slight "in flight" load still making it's way through the mash at that point shouldn't be enough to hurt your numbers.
If your flow rate through your mash is painfully slow, you might look at your lauter geometry and see if there's some improvement to be made. Also rice hulls can loosen up a thick mash.
