I think I figured out how much water I’ll need so that I end up with 5 gallons in the fermenter. Please have a look at my math and correct if necessary (go ahead, I can take it)
I’m starting with 10.13 lbs. of grain.
I’m figuring 2 quarts per pound of grain in mash for a total of approx. 5 gallons.
I’m figuring .12 gallons of loss to grain absorption for a total of approx. 1.2 gallons.
Equipment dead space loss = approx. 1/2 gallon.
Evaporation loss due to boiling = 1.5 gallons.
1.5 gallons loss in boil seems a little high. I could be wrong. But I do a 60-90 minute boil (depending on what I’m brewing) and usually only lose 1/2 to 3/4 gallon.
My mash tun is a converted 48 quart Igloo Icecube cooler. I’m using a 1/2" braided SS hose in the mash tun connected to a brass 1/2" ball valve. My kettle is a SS 30 qt. pot and an 80,000 BTU propane turkey fryer. I’m using 6.5 gallon HDPE buckets for fermenting and bottling. I have a home-made 3/8" copper immersion chiller. If there’s anything else you need to know, let me know and I’d be happy to post it.
I am assuming that you are batch sparging. You water amount might be a little a high especially with a 30 qt boil pot. You might want to try mashing with 4 - 4.5 gal and sparging with 3.5 gal.
Why the magic 8% - 15% number? That’s a new one on me. I shoot to get to my target fermenter volume (and thus final gravity) as opposed to a percentage boiled off. I guess to get it to a range of percentages I could adjust the volume of my mash/sparge water volume, but that seems like a pain. I just use the same water/grain ratio for every target gravity and adjust volumes during or after the boil to hit my gravity.
The 8% is an approximation of the boil-off required to remove DMS, which is probably only a problem for brewers using Pilsner and (maybe) “American 2-row” malts. I’ve never seen any hard data nailing down the 15% value, but it’s an attempt to quantify the observation that an aggressive or unnecessarily long boil can introduce undesirable flavors. I don’t know what size batches you brew, but 2.5 gallons is a pretty high percentage for even a 10 gallon batch.
I’m not saying that you really need to temper your boil, your high evaporation may be due to something like your kettle geometry and may have little negative impact on the beer’s flavor. However, it might be worth giving it a try and seeing if you prefer the flavor. I don’t know any brewer that doesn’t think their beer could be improved, even if it is already darn good.
I lose 2 gallons per hour and that’s with about as gentle a boil as I’m comfortable with. My kettle is pretty wide and I believe that’s the culprit. I used to worry about it but short of getting a new kettle there’s nothing I can do about it. So I’ve found other things to worry about instead.
I use a 14 gallon kettle for 10 gallon batches (11-12 gals starting out in kettle), so I watch my boil closely. On avg. I think I lose a little over 1 gallon during my boils (for a 60 minute boil). My last batch came up a bit short as a result (first batch brewed in a few years).
For 5 gallon batches, I shoot for an ending wort size of 5.5 gallons into the fermenter. After fermentation and the yeast settling out takes up volume, not to mention the racking cane’s “widget” to leave most of the flocculated yeast behind. Anyway, it will take a few times to hit your target. Take good notes of each batch so, you can duplicate your results or at least know what to expect from your system. Good Luck and let us know how it turns out.
