Water left in mash tun?

[BesteBrew]

I am dialing in my process for all grain and I have been using the numbers beersmith has been giving me in terms of volumes of water to add. When I finish the sparge and hit my preboil volume I always have about 3/4 of a gallon in my mash tun still. Should I be draining the whole mash tun volume or stop when I hit my preboil volume?

 

[diS]

Try to optimize volumes so you don't have any wort left in MLT (or at least minimize it) when hitting preboil volume.

 

[brewkinger]

Try to optimize volumes so you don't have any wort left in MLT (or at least minimize it) when hitting preboil volume.

This.

Mash then drain first runnings.
Calculate volume and then sparge with whatever volume you need to get to preboil volume.

After first runnings, the grain will not absorb any additional water, so sparge water in = sparge water out.