I just started BIAB mashing in 1 pot @ 150 degrees for an hour then I batch sparge in another pot for 10 mins @ 170 . I usually do a three gallon batch with about 7# of grains . I use a 1.5 qt to lb water ratio , I fill my boil pot up and usually have some water left in my sparge pot. Foes anyone see a problem adding the remainder of the sparge water at the last 15 mins of the boil to help ?