I Outgrew the Cooler
Like a lot that move to all grain, you start out with a 10 gallon water cooler. They work exceptionally well, holding a temp with only a 1°F drop over the course of an hour (on a really cold day). But, I wanted to make some bigger beers. At most, the cooler could hold about 12kg of malt @ 2.5L/KG of water.
