Low final volume-possible reasons?

Yesterday my buddy & I brewed our first batch of all grain. Everything seemed to be going very well until we transferred the wort into the carboy and ended up with about 3.5 gallons, well shy of our goal of 5 gallons.

When we started cooking the wort we had between 5.5-6 gallons. Is this a normal amount of volume loss?

Our brew kettle is fairly large, 15 gallons, so the wort was not very deep inside of it. Would that have caused more water to burn off?

Did we have had the burner up too high?

These are the possible reasons we have come up with. Anybody have any ideas? Any advice or suggestions are appreciated.

Most likely cause is that you boil off more than you thought you would. You boiled off 1 gallon a half hour, which is what I get with my 15 gal pot. Try starting off with 7.5 gallons preboil to get you 5.5 post boil. You'll match almost every time.

In general, the wider the pot, the more boil off.

I always got to caught up in the brew day to acurately determine the boil off rate and always got less than my desired 5 gallon return. So one day I filled my kettle with 5 gallons of water and boiled for an hour; tried this twice. The first time lost 2.25 gallons in an hour, very vigorous boil. Second try, I boiled nearer a gentle boil and lost 1.3 gallons.

I also loose about half a gallon or so to trub. So sounds like you're loosing about the same rate as I do. Try to start with more like 7.5 to 8 gallons next time.

My boil kettle is a 15.5 gallon keggle.

Thanks for the quick responses guys!

LeonardZelig said:

Y
When we started cooking the wort we had between 5.5-6 gallons. Is this a normal amount of volume loss?

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So when you started the boil you had 5.5-6 gallons? What was your starting gravity and your final gravity?


All boil kettles are different, so it is good to monitor your boil off rate for your first few batches. Typical you want to shoot for 10-15% boil off per hour, for most pots you will achieve this with a nice low boil. You don't necessarily want a very aggressive boil.

If you started with 5.5-6 gallons of wort and ended with 3.5 , you had close to a 40% boil off. How long did you boil?

Assuming a 15% boil off rate with a 60min boil for a 5.5 gallon batch, you should have started with ~6.3 gallons.

If you hit your starting gravity, you most likely left behind your missing wort in the mash tun. If your starting gravity is much higher than you anticipated you might not have sparged with enough water.

hope this helps.

Bsquared said:

So when you started the boil you had 5.5-6 gallons? What was your starting gravity and your final gravity?


All boil kettles are different, so it is good to monitor your boil off rate for your first few batches. Typical you want to shoot for 10-15% boil off per hour, for most pots you will achieve this with a nice low boil. You don't necessarily want a very aggressive boil.

If you started with 5.5-6 gallons of wort and ended with 3.5 , you had close to a 40% boil off. How long did you boil?

Assuming a 15% boil off rate with a 60min boil for a 5.5 gallon batch, you should have started with ~6.3 gallons.

If you hit your starting gravity, you most likely left behind your missing wort in the mash tun. If your starting gravity is much higher than you anticipated you might not have sparged with enough water.

hope this helps.

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Just want to add my $0.02 on judging boil off using percentage points...It's generally not a great way to determine your boil off. Your boil off will more than likely be a static number regardless of boil time. Therefore boiling at 90 minutes would cause you to think you have a larger boil off rate, when in fact you still boil of X gallons per half hour.

This is a big problem people had with the first beersmith, boil off should not be a percentage.

Evaporation rate of your burner - you need to get an idea of how much you evaporate per hour.

Water increases in volume by around 4% when it is heated, so if you have 6 gallons at flameout, you'll have around 5.75 gallons after the wort cools.

Hops retain some water.

Hop material and hot break / cold break make up a certain volume of the trub in the bottom of your kettle.

My friend and I use a keggle and our evaporation rate is about 1 gal per hour. We don't have a super vigorous boil like some other people have.

This past weekend we had 13 gallons at flameout, and we got about 11.9 gallons into the carboys after everything was said and done. We were shooting for 12, so we were pretty satisfied with that.

To reiterate what many have already said........ Two gallons boil off per hour is not unusual. You don't need to change a thing about your process. Just adjust your preboil volume accordingly for the next batch.

Once you know how much you boil off is, life is easy and you will hit your volumes easily.

As far as hop absorption and trub loss goes this a completely different issue. Simply scale up your batch size to accomodate this. I.e. do a 6 or 6.5 gallon batch for ipas.

It's good practice to measure the trub volume (as well as how much you got into the fermenter) for your first few batches so you can get all your volumes nailed down......

TheMan said:

Just want to add my $0.02 on judging boil off using percentage points...It's generally not a great way to determine your boil off. Your boil off will more than likely be a static number regardless of boil time. Therefore boiling at 90 minutes would cause you to think you have a larger boil off rate, when in fact you still boil of X gallons per half hour.

This is a big problem people had with the first beersmith, boil off should not be a percentage.

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Okay, so what you are saying in determine how many gallons will boil off in an hr for a given pot and a consistent boil rate. Then no mater if you are boiling 5 gallons or 12 gallons, you know that X gallons will be boiled off. This sound right?

I guess the problem I see with this is that you need to have a consistent boil rate between all your batches. And for the OP he is inquiring if his boil was too hard. As I see it, you have three variables: Volume, Boil kettle, and heat applied to boil. With your method, you are holding the boil kettle and the heat applied constant. Where the OP is asking if the heat was up to high.

I think, like with all things brewing there are many different ways to do things. But I do see the logic of your method and like it.

To really make a better analysis of his problem we need to know target and actual starting boil gravity and post boil gravity.

The hydrometer reading post-boil was 1.052, taken at about 73F so if we add .0011 according to Palmer's How to use Hydrometer, it may have actually been 1.053. I believe our goal was 1.047 or so. I do not believe we took a reading pre-boil. Is the pre-boil reading what we want to look at for efficiency?

Bsquared said:

Okay, so what you are saying in determine how many gallons will boil off in an hr for a given pot and a consistent boil rate. Then no mater if you are boiling 5 gallons or 12 gallons, you know that X gallons will be boiled off. This sound right?

I guess the problem I see with this is that you need to have a consistent boil rate between all your batches. And for the OP he is inquiring if his boil was too hard. As I see it, you have three variables: Volume, Boil kettle, and heat applied to boil. With your method, you are holding the boil kettle and the heat applied constant. Where the OP is asking if the heat was up to high.

I think, like with all things brewing there are many different ways to do things. But I do see the logic of your method and like it.

To really make a better analysis of his problem we need to know target and actual starting boil gravity and post boil gravity.

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That is correct. If you boil the same and use the same kettle your boil off should be constant regardless of volume.

I would like to assume that most brewers boil at the same level of vigor every time they brew. I know I aim for a certain level every time, I assume you do as well. Most either boil the hell out of it, or maintain a low rolling boil. As long as you do the same thing every time then your results will be relatively consistent. In brewing, the name of the game (as you know) is consistency, so if you're boiling as hard as you can one batch and then just barely managing a roll the next then you're not going to get your best results every batch anyway.

So if the OP keeps the same boil for every batch, then he will see similar results, I.E. boiling off a gallon/half hour. Whichever level of boil you choose, doesn't really matter, as long as you do it the same every time. (A lower, rolling boil will save a bit on propane...)

I do agree that to know the exact answer then his gravity numbers would be helpful. However, he started with 5.5-6 gallons pre boil and ended with 3.5. He was aiming for 5, so it just seemed clear to me that he underestimated his boil off.

There are many different ways, and if you like to use one method over another then by all means. From my experience this is the simplest.

TheMan said:

In brewing, the name of the game is consistency...

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exactly.

According to the numbers you posted a 1.053 OG from 5.5 gallons, your original start gravity would have been around 1.034.

If you wanted to hit 1.047 you would have had to start with a volume of ~6.8 gallons to end up with 5 gallons at 1.047 with your current boil off.

I don't know if this helps, but to me you and ether throttle back your burner a little and increase your sparge volume, or you can just increase your sparge volume assuming a 2 gallon/ hr boil off.

OK, I want to ask a dumb question. What does the SG into the boil and SG after the boil mean? Or a better question is what SG do i initially need to start with to get 5.5 gallons of a 6.5% beer after an hour boil? I know I can't start out with 5 gallons beause water boils away. Is there some simple formula (for math illiterate people like me) to figure out what post boil original gravity will be with a given preboil SG and 15% boil off rate and get at least 5 gallons into my keg?

(preboil gravity) * (preboil volume) = (postboil gravity) * 5.5

in other words

(preboil grav * preboil vol)/5.5 = postboil grav

Grumpybumpy said:

(preboil gravity) * (preboil volume) = (postboil gravity) * 5.5

in other words

(preboil grav * preboil vol)/5.5 = postboil grav

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For this equation to work, you will have to convert to Plato, or remove the 1 from the specific gravity ?

(1.034*6.8)/5.5= 1.27

1+((1-1.034)*6.8))/5.5) =1.042

At leasts thats my math.

Bsquared said:

For this equation to work, you will have to convert to Plato, or remove the 1 from the specific gravity ?

(1.034*6.8)/5.5= 1.27

1+((1-1.034)*6.8))/5.5) =1.042

At leasts thats my math.

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Yeah, you need to subract the 1. Otherwise you're essentially scaling up the density of the water as well, and that's no good.

Bsquared said:

For this equation to work, you will have to convert to Plato, or remove the 1 from the specific gravity ?

(1.034*6.8)/5.5= 1.27

1+((1-1.034)*6.8))/5.5) =1.042

At leasts thats my math.

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discnjh is correct...should be

1+((1.034-1)*6.8))/5.5) =1.042

TheMan said:

discnjh is correct...should be

1+((1.034-1)*6.8))/5.5) =1.042

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oops, thanks.