Originally Posted by vadem
How much wort would you all say evaporates off during the boil?
My 4gal pot boils off .875gal per hour. I've calculated it out though that's how I know. I would assume if you start about 1gal higher than your final volume you should be close.
If you want to conduct an evaporation test, you'll have a closer idea of your rate. Just get 2 or 3 (preferably 3 since that's your boil size, or close to it). Then set the timer for 60 minutes once the boil starts and take a measurement after the boil is over. Remember too that water expands as it's temperature rises and contracts as the temperature drops. Your volume of water just after you turn the heat off will be about 4% more than when it's chilled to pitching temps.
The other thing to factor is the amount that evaporates off while your heating the water up to boiling. All these tests and measurements are by no means necessary, it's part of dialing in your system though. Good luck!