I'm doing a bunch of research on partial mash brewing, with the hopes of evolving out of extract brewing into partial mash. I was looking at recipes on beertools.com and this is probably a dumb question but I was wondering, is the batch size the same as the amount of water that I should have in my pot when the grains/extract is added? Like if I'm aiming for a 5 gal batch does that mean I need 5 (or more due to some boiling off) in the pot off the bat or can I do it like an extract recipe kit where the boil is at about 3 gal and I add 2 gal of water to the fermenter?