[Pinski]

I recently picked up a gently used Blichmann 20 gallon boil pot for a great price. I remember the guy I bought it from saying he lost a lot to boil off.  Does anyone have experience with this boil kettle to provide a tip on what I can resonably expect to boil off per hour of vigorous boil to evaporation?  Thanks in advance.

[bluesman]

It will depend on the vigor of the boil, but I can tell you that I lose about a gallon per hour with a moderate boiling action in my Blichmann 15. I recommend trying to maintain a moderate boiling action whereas you achieve a rolling action on the top of the wort. Vigorous boiling isn't really necessary and is a waste of propane IMO.

[Bret]

I agree, I use a 6 gallon pot on the stove for 5 gallon batches.  It boils, but not like crazy.