So I just upgraded from a Coleman cooler mash tun to a 15 gallon stainless with a false bottom that sits 2 inches above the bottom of my kettle. I filled my mash tun with water until the level reached to the top of the false bottom. I measured this volume to be just under 2.5 gallons. I then added the water back into the kettle and proceeded to drain the water through the valve. After the draining stopped I then measured the undrainable volume in the kettle to be 1 gallon. My question(s) is when I mash in I will not be able to stir the water below the false bottom. How do I calculate this volume back into my equipment profile? Since I can't stir this water do I add 2.5 gallons on top of my calculated strike water? Also since I can't stir the water below the false bottom will this water down my wort? Or do I subtract it out of my sparge water?