I would like to double the size of my batches from 5 gallons to 10 gallons without changing equipment.
For example, let's say I have a 5 gallon recipe for an IPA. I know my mash cooler is big enough to mash at least double the grain bill for my 5 gallon recipe (I have brewed 5 gallon batches of strong ales which easily have more than twice the grain of my 5 gallon IPA recipe).
If I mash twice the grain for my 5 gallon IPA recipe, then just boil the ~6 gallons of wort (and double the hop additions), can I then split the higher OG 5 gallons of wort into two fermenters (2.5 gallons in each) and top off each fermenter with another 2.5 gallons of distilled water each?
I know mash and boil times will be extended due to the higher grain/OG, but is there anything inherently problematic with "watering" down a higher concentration wort to double the batch size?