I like to brew 2 batches at a time. I have 2 5G brew pots and like to boil 4.5G or as much wort as I can without boiling over, which means I boil over from time to time trying to work 2 batches at once topped up as high as I can.
My wife just gave me 2 85 QT (8.75G) brew pots so I can still...