Extract brewing is exactly where my idea of topping up came from and it does have it's advantages. You can make larger batches without a large kettle so you're really only limited by the size of the fermenter. I've thought about doing a kettle sour this summer but I have the problem that I just don't have the space to leave my kettle in the kitchen for 2-3 days after pitching the lacto before the boil and I really don't want to carry a kettle with nearly 7 gallons down to the basement and back up. So I've decided that as long as I'm brewing in the kitchen that if I do it I'm either doing an extract batch or I'm going back to doing a more concentrated BIAB batch and topping up in the fermenter.well, 2.5 gallons for my setup is going big
using Brewfather, there is a setting for "top-up" and it looks like that's exactly what i need here. i changed my recipe to target 2.5g, instead of 2g, and it automatically scaled ingredients to that volume. then i adjusted "top-up" accordingly. only the bittering hops were automatically scaled up a bit after that change. i think this is totally cheating, but i'd love it if it works!
i have no experience with extract brewing, but isn't the idea similar in that you work with concentrated wort and top-up in the fermenter?
does it matter if the top-up water is boiled or not? Brewfather suggests that it be cold and actually that would help cooling of course.
also, i am not making water adjustments, but i suppose that could be affected as well.
Typically if it's safe to drink it's safe to top up with (watch the chlorine though) but boiling reduces the risk of contamination. When I topped up though that way I just used tap water run through a carbon filter.
