Thanks for the confirmation on this. So with a 5 gallon batch how much do you typically boil? For kits they call for 2.5 gallons which I follow but don't really know the magic behind the number.... why 2.5 vs 5 and is there any difference in more vs less?
I wouldn't depend on "typical" - it's all dependent on your own setup. You have a pretty skinny tall pot, which means that you have less surface area, which means you'll boil off less per hour than my short wide pot.
Kits call for 2.5 gallons for those of us that can't do full boils. You can definitely do full boils.
So what you should do is carefully measure about 3 gallons of room temp water and put those in the boil kettle and get the water to a boil and then start a timer and boil the water for half of an hour. Let the water cool to room temp again and then measure the water again and figure out how much water you lost to evaporation. Double that number and then you'll know how much water you'll be boiling off in a typical 60 minute boil.
That's one thing you'll need to know. Other things you'll need to know:
* How much the wort is going to shrink when it goes from boiling temps down to yeast pitching temps. Known as "shrinkage." Your wort will shrink approximately 4% in volume going from boiling to room temps.
* How much wort you leave behind in your kettle / tubing when you drain from the kettle to your fermentor. This is known as "deadspace loss."
* How much beer / trub you leave behind when you transfer from your fermentor to your bottling bucket or keg. This is known as "trub / fermentor loss."
* How much beer you leave behind in your bottling bucket, if you bottle. This could be added to the fermentor loss.
So let's say you want 5 gallons of finished beer.
You lose a negligible amount of beer to your bottling bucket, so you don't even worry about this. Still 5 gallons needed.
You lose about a quarter gallon to your carboy, so you need 5.25 gallons of beer.
You lose about a half gallon of wort to the deadspace in your boil kettle / hops left in the bottom of the boil kettle absorbing wort / wort left in your tubing. So you need 5.75 gallons of room temperature wort at the end of the boil.
You lose a gallon of wort in a 60 minute boil, so for a 60 minute boil, you'll need 6.75 gallons of room temperature wort before the boil.
The wort will expand 4% when it reaches boiling temps, so add another 4% to the 6.75 gallons and...it looks like you'll need 7 measured gallons of boiling wort at the beginning of your boil.
That will get you pretty close to your pre-boil amount.
If you want to get even
more precise...wort shrinks about 2% from boiling temps to mashing temps, so subtract 2% from 7 gallons and you'll need 6.9 gallons of wort at mashing temps.
