Thanks Brad , actually though my problem is that , for example, say I add 3.5 gallons to the mash tun on the initial infusion . After mashing , when I transfer to the boil kettle I only end up with about 2 gallons. The tun drains fairly well so I dont have a big reservoir of undrained mash . Also , after I see what I am short for making my target volume , thats how much water I add for the batch sparge and in that step ( same tun , pump , grain bed , everything) I dont lose any volume. Thats why I thought the grain was absorbing more than what the software was figuring.Your thoughts?