Boil losses - Way more than I expected

[Turk10mm]

So after several full boils that ended up in adding water to the fermenter I decided to do a full mock boil tonight and see just where I am. I did a mock minimash for 45 minutes at 155, then brought to a boil, simulated adding extract time, brought back to a boil and boiled for an hour.

I started with 7 gallons of water and ended up with 4 3/4 gallons of water after chilling from boiling to 75 in 14 minutes.

So that means that I have 2 quarts to play with between adding extract. I guess I'll be measuring out my extract to see how much it is prior to the boil and then adding that much water to make a total of 7.5 gallons.

That seems really high, but it is what it is.

I also used 3.2lbs of propane for the entire batch, so I found out a bunch of things tonight.

 

[Ace_Club]

Don't forget that not all of that is boil off volume. You should calculate the amount of boil off losses before cooling. Cooling the wort will result in about 4% volume contraction. So, your actual boil off loss would be only 2 gallons per hour. (7 - (4.75/.96))