How much boil off can I expect?

[the75]

I'm trying to figure out how much water I can start off with for a final 5.25 gallon batch. This is my first time doing a full boil in my newly created 15.5 gallon sanke keg brewpot. I was planning on starting out with 6 gallons of water. This is a newbie extract brew session only. Is 3/4 gallon boil-off a good general estimate?

 

[Pie_Man]

You can approximate this by boiling a known quantity of water for an hour and seeing how much is left. 0.75-1 gallon per hour are reasonable starting assumptions. You may want to assume 1 gallon to ensure you get your desired volume. In my opinion, it's best to estimate a higher rate when starting out. If you're wrong, you have more beer, or you can boil a little longer.

 

[the75]

Great idea! Thanks. I need to do a test boil anyways. Appreciate the help.

 

[jCOSbrew]

For extract also make sure you account for the volume of your DME. 6 lbs is about 1/2 gallon.

 

[gwdraper4]

I would start with estimating 15-20% boil off, but this can vary depending upon your type of vessel and how vigorous your boil is. If you are using a converted Sanke and a moderate boil, I would start with 7 gallons of wort in your pot. This should boil down to 5.6-6 gallons in an hour, then you'll probably leave behind 1/2 to 3/4 of a gallon in your Sanke giving you a touch over 5 gallons in your fermentor. One thing that is good to do with a new pot is have a trial run with just water or at least see how much liquid will be left in the bottom when your outflow stops. The trial run is great because like I previously mentioned all pots and burners act slightly differently, so by somewhat figuring out what to expect you can calculate your recipe accordingly. Also...it is good to put all of your DME in a bucket then fill up with water while dissolving to a known level. This will help account for the volume of the DME. Cheers!

 

[TopherM]

Boil off rate is a direct funtion of the diameter of your pot, so it is very specific to your actual pot. The best thing you can do is, like the other poster said, is figure out the boil off rate for your specific pot with just some water, and you can use that number going forward.

Also remember that you will lose some volume to grain absorbtion (significant if you are AG, not so much for extract), some volume to cooling (around 0.2 gallons for a 5.0 gallon batch), and some volume to trub post-fermentation (0.25-0.5 gallons for a 5.0 gallon batch). Factor in these numbers along with the boil off when you calculate your starting volume.

Good luck!

 

[the75]

Great info! Thanks everyone. I have some work to do!

 

[A-Juice]

thanks for the advice to consider the volume of the DME. Do you think that there is a net zero volume between adding 1/2 gallon of DME and the volume you lose to the grain absorbtion?

Also, if you are trying to achieve the target original gravity, would it be a better strategy to overestimate the water to make sure you still have 5.25 gallons when you are done or would you be better off undershooting by a gallon or less and topping off?

I thought about starting with 5 gallons and then topping to 5.25 after boil off and vessel transfer losses.

 

[user 108580]

Also keep in mind that you will lose some volume when the Wort cools to pitching temperature due to contraction. It's not much but it is noticeable.

Edit: didn't see that somebody already mentioned this above.