Determining Pre-Boil Volume

[bhambrew]

I'm gearing up for my first AG brew using keggles for my MLT and BK, and after two hours of searching the forums I still can't figure out what my pre-boil volume should be in the BK. Looking for some advice from keggle brewers out there...

-Brew size will be five gallons.
-Evaporation rate is just over 1 gal./hour based on "wet run" test of the BK.
-After draining all of the liquid out of the BK by gravity, approx. 1 gal. of liquid is left in the bottom of the keggle. I will be using an IC and circulating the wort during cooling to create a whirlpool. Here is a shot of the inside of the BK:

I usually use whole hops, but the first recipe will use pellet hops.

So, if I want to end up with 5 gallons of wort in the fermenter, how much volume should I have in the BK for the start of the boil?
My logic is this: 5 gallons (target fermenter volume) + 1 gallon (evaporation) + 1 gallon (left in the bottom of BK) = 7 gallons of pre-boil volume in BK?

After sparging I will end up with less than 7 gallons (I think), so should I just add water to the boil kettle pre-boil to reach my target volume? Thanks for the help!

 

[dzlater]

My logic is this: 5 gallons (target fermenter volume) + 1 gallon (evaporation) + 1 gallon (left in the bottom of BK) = 7 gallons of pre-boil volume in BK?

After sparging I will end up with less than 7 gallons (I think), so should I just add water to the boil kettle pre-boil to reach my target volume? Thanks for the help!

Your logic is correct
No reason you can't sparge til you get 7 gallons
however if you do come up short you can top off

 

[Ridonkulous05]

I apologize, as I brew out of B3 kettles, but your keggles should have superior performance (as far as lower boil-off rates) than my wide mouth kettles at a given boil rate, due to lesser surface area for a given volume (smaller diameter mouth) for a keggle.

I cannot give you hard and fast rules for how much wort will be lost at a given phase during your process, as a number of loss occasions have variables built in. Below are examples:

Loss opportunity; (variable affecting potential wort loss):

-Water evaporation during mash (dependent on mash vessel, number of times stirred, time lid off, etc. [not a big deal, as this is a small quantity and easily replaced with extra sparge water])
-Grain absorbtion during mash (dependent on types of grain/adjuncts used, crush of the grain, geometry of mash tun, and manifold vs screen vs. braid)
-Boil-off/boil kettle: (dependent on diameter of kettle mouth, duration lid is off, number of boilovers [d'oh!], loss to hop absorbtion [varies by hop type], rate/vigor of boil, and kettle geometry/where outlet tube draws wort, etc.)
-4% wort loss upon cooling (consistent, due to properties of boiling vs. cool wort)
-loss to trub in primary -I know you're talking about just fermenter fill volume, so this is an afterthought, but this affects total yield (dependent on straining apparatus between boil kettle ant fermenter)
-I might be forgetting at least on potential loss opportunity here...

You hit almost all of the above in your initial post, minus loss to grain absorbtion during mash, perhaps.

After seeing the variables involved above, you can see that EXACT numbers that you will arrive at are going to be peculiar to your particular brewing equipment, methods, and "style" (boilovers are my forte' right now). Therefore, your exact numbers will be discovered only by empirical experimentation.

However, you seem to have a good estimate of where to start from. 7 gallons sounds typical for 5 gallons going into fermenter after a 60 minute boil.

When trying a new beer style, I tend to err on the side of trying to achieve near the maximum OG for a given style when putting together my grain bill, just in case I have low efficiency or use too much water. Additionally, I either: always have an extra fermentation vessel standing by "just in case" I have more post boil wort than I originally expected, or I anticipate underfilling two vessels of smaller capacity, etc. This way, if I overshoot my post-boil wort volume, I do not waste that precious, beautiful wort... (Often, I keep a large, 5L growler standing by with an appropriate size stopper and airlock, just for overage... I haven't had to use it yet.)

As far as top-up of your pre-boil volume, I would say this: If you have a means to heat this "top-up" brew water to sparge temperatures, then run that top-up volume through your grain bed when adding it to your boil pot. If you do not have a means to heat that final addition, then, yeah, just add it to your kettle before the boil.

I am STILL in the experimentation phase, because between each batch I have been adding a piece of equipment that affects the above variables! Shucks! At least these equipment additions make my process more streamlined and (eventually) repeatable, when I stop buying/adding new "stuff".

As fun and exciting as prepping for a new batch is, I can't help but worry and re-scrub my wort loss calculations, my mash profile, yadda, yadda every time. I know- RDWHAHB, but this obsessing is a twisted part of the fun/learning process for me.

The bottom line is, if you end up with 6 gallons of low-OG or 4 gallons of high-OG beer, the odds are that you will have an awesome beer, anyway. Then, after this batch (if you take good notes) you will also have a better grasp of your methods and setup so that you will "nail" that perfect 5 gallon fermenter volume (At which point you will want to go to 10 gallon batches- Phooey!).

I wish you the best of luck!!!

 

[bhambrew]

Your logic is correct
No reason you can't sparge til you get 7 gallons
however if you do come up short you can top off

Thanks for the information. From what I gather reading the forums, I will sparge until (A) I reach my target pre-boil volume (7 gallons in this case), or (B) the wort coming from my MLT drops below a gravity of 1.010. If the wort drops below 1.010 before I reach my target volume, then I top off and end up with lower gravity wort in the BK. Does this sound right?

Thanks again for the reply.

 

[bhambrew]

Ridonkulous-

Thank you for the very thorough and informative reply! Like most folks I'm sure my first AG batch will not be without its share of frustrations but, I have never been more excited about brewing.

As far as top-up of your pre-boil volume, I would say this: If you have a means to heat this "top-up" brew water to sparge temperatures, then run that top-up volume through your grain bed when adding it to your boil pot. If you do not have a means to heat that final addition, then, yeah, just add it to your kettle before the boil.

I do have the means to heat "topping off" water (the HLT is also a sanke keg with dedicated burner, and I'll be sure to fill her up for the first brew, just in case). My understanding is that I should stop sparging when the wort drops below 1.010, in which case I would simply top off directly into the BK.

The bottom line is, if you end up with 6 gallons of low-OG or 4 gallons of high-OG beer, the odds are that you will have an awesome beer, anyway. Then, after this batch (if you take good notes) you will also have a better grasp of your methods and setup so that you will "nail" that perfect 5 gallon fermenter volume (At which point you will want to go to 10 gallon batches- Phooey!).

I wish you the best of luck!!!

Thanks for all the great information. I have a few remaining tasks to complete before the first brew on the new system, and hopefully everything should be ready for a brew day by next weekend. I will be sure to post the results of the first brew here. Also, if you are interested, here is a link to the build thread.

 

[Ridonkulous05]

Bham,

Wow! After checking out your rig, I am envious of your setup!

I look forward to hearing of your results!

I am tracking what is always said about stopping sparging before the 1.008 mark, but is there really anyone who sits there and takes hydrometer samples every minute until they reach that magic 1.010 or 1.008? ...and if they do, and they still have 2 gallons of sparge to drop before they reach their pre-boil volume, what do they do? Do they quit? I mean, you are totally right, but after reading that so many times, I have wondered how practical it is, and then I have wondered how many people have really run into tannin extraction problems if they are not maximizing a commercial yield while brewing a BMC clone... In other words, for all of the brews that I have done (even the low OG ones,) I do not think that I have run into a time where my runnings have ever approached 1.010 or 1.008... ...but I am off topic and ranting now-

I am living vicariously through you to see your rig put to good use for humanity! May your first AG be an awesome one! (I'm sure it will be!!!)

-Brew safe, brew strong, brew well!!!

 

[bhambrew]

Bham,
I am tracking what is always said about stopping sparging before the 1.008 mark, but is there really anyone who sits there and takes hydrometer samples every minute until they reach that magic 1.010 or 1.008?...

I have wondered how many people have really run into tannin extraction problems if they are not maximizing a commercial yield while brewing a BMC clone...but I am off topic and ranting now-

-Brew safe, brew strong, brew well!!!

Thanks again for the words of encouragement. I will post the results of the brew as soon as its in the fermenter.

Leading up to my first AG brew I have been doing as much research as I can, and always see the warnings about sparging beyond 1.008. Problem is that I couldn't figure out how in the world, when brewing 5 or 10 gallon batches I was going to effictively use my hydrometer to measure the gravity on the fly during the sparge. My paranoia finally got the best of me and I ordered an ATC refractometer.

So, if I can keep my $hit together during the first AG brew day I will try and use that tool to monitor my wort gravity during the sparge. I'll keep good notes and report my finding here.

Maybe someone with experience using the refractometer or hydrometer during fly sparging will chime in with some advice? Thanks guys.

 

[phatuna]

There are a lot of great tools to help you figure out your mash and sparge volumes, I use this one: http://www.brew365.com/mash_sparge_water_calculator.php

I also boil from a keggle and boil off about 1.5 gallons per hour on a slow roll. You can enter all of this data into the link that I gave you.

It will tell you how much mash and sparge water to use. As well as your strike temp. You will want to experiment with mash thickness. 1.25 or 1.3 quarts of water / lb of grain is a good place to start, some folks go as hi as 2 and can go as low as 1 or so.

 

[bhambrew]

After months and months putting this thing together I finally attempted my first AG brew yesterday...and I am very happy with the results! Total brew time was about 7 hours from when I first filled the MLT with water until everything was totally clean and the lights were out in the brew shack, not too bad.

Best of all, I ended up with 5.5 gallons of brew in the carboy, and only a few points away from my target OG!

I used the Refractometer and Hydrometer to take measurements throughout the brew session and kept copious notes. I input the data into the calculators at brewersfriend.com and came up with the following results:

Pre-boil wort collected: 7.5 gallons
Pre-boil gravity: 1.034
Based on my grain bill, that comes out to 79 % efficiency, sweet!

Post-boil volume was 5.5 gallons in the carboy with a gravity of 1.040 (target for this recipe was 1.044).

I do have some questions for the AG veterans out there- see next post...

 

[bhambrew]

The brew was "Dawson's Multigrain Red" kit from NB:

Grain Bill
7.75# Rahr 2-Row Pale
0.5# Weyermann Caramunich II
0.25# Weyermann Caramel Wheat
0.25# Weyermann Chocolate Rye

I heated 4 gal. strike water (I have a little more than 1 gal. of dead space below the false bottom) to about 164 deg F, and after adding the grain the mash was at 154 deg F (target temp 152 deg F).

After about 45 minutes the mash temp had dropped to 150 deg F, so I slowly recirculated using the pump and added some heat for a few minutes.

At 60 min. I fired up the burner again and started to recirculate until the temp was up to 172 deg F. Then, turned off the heat and rested for 10 min. The sparge water was heating during the mash, and up to about 175 deg.

After the mash out, I started sparging with the 172 deg. sparge water. As expected, it took me a little while to balance the rate of water coming in with wort going out, but eventually I got it figured out, and kept about half-inch of water covering the grain bed. I tried to sparge very slowly, with the valve on the outlet side of the pump barely open. At this slow rate it took me about 55 minutes to get my total pre-boil volume of 7.5 gallons in the BK.

Question: After about twenty minutes of sparging, the temperature in the MLT started to drop. I added heat to the HLT to keep the sparge water temp up above 170, but by the end of the sparge, the temp in the MLT was down around 140. Is this okay? Should I be adding heat to the MLT during the sparge to keep the temp up around 172?

Other than the temp dropping during the sparge, everything else was as planned. By the time I had 7.5 gallons in the boil kettle the wort coming from the MLT was down to about 1.008.

Using the pump to create a whirlpool in the boil kettle during cooling seemed to work great, most of the pellet hop trub remained in the kettle. My immersion chiller cooled the wort from boil to 75 degrees in about 20 minutes with cool tap water. Icing on the cake was the foam snake- this was the first time I have used StarSan!

Thanks for the Help!

 

[Starderup]

If it was me, I'd keep sparging until I got my pre-boil volume. Even 1.010 wort has more sugar than 1.000 water.
Nice BK!
If you haven't tried BrewTarget yet, I would recommend downloading and installing it. You should input your equipment parameters, and it will tell you exactly how much water to heat. I have found it very accurate.

 

[suprchunk]

If it was me, I'd keep sparging until I got my pre-boil volume. Even 1.010 wort has more sugar than 1.000 water.

And tannins.

 

[Starderup]

And tannins.

Duly noted. However, if your crush is right, the husks are going to be largely intact, and if your grain bill is on the money, no worries.
But I didn't think about that, mainly because I use BrewTarget!

 

[bhambrew]

Thanks for the advice...as it turns out, I ended up with my target pre-boil volume without crossing the dreaded 1.008 mark. What I am more concerned about was the temperature of the mash dropping during sparging.

Is it recommended that I continue to heat the MLT after mash out & during sparging to keep the temp up above 170 F, or just worry about the sparge water temp? Thanks.

 

[Starderup]

Once I dump in my sparge water, I just try to get my volume. I don't worry about temps at all. The beer that comes out meets my standards. YMMV!