I brew 18.5 liter batches on my 6.5 anvil brewing system and it is awesome. The boil can be a bit worrisome but if you ad some FermCap s to the boil - it won't boil over and I am at 21.5 liter boils. Praise the Lord - no boil overs, no mess but I do have to ad about 1.5 liters to the fermenter...