I have 25 pounds of grain mashed in with 1.25 qts per pound. How much water should I lose ( assuming no dead space in the tun) to grain absorption? For some reason I am having a heck of a time figuring it out.. last beer was 17 pounds of grain and I lost 1.5 gallons. I am figuring 2 gallons but for some reason that does not seem right to me