how to measure wort volume?

I did my first AG last week, and one thing that came up is this: I had no idea exactly how much wort I actually had in the pot, before, during, and after the boil. This seems like a pretty critical element that you would want to track.

you can't simply assume all of the water that goes into the tun comes out. there is some loss due to grain absorption, and a loss due to the tun drain not being exactly on the bottom. So, I'm assuming you typically sparge until you get you 6.5 gallons (or whatever you want to account for boil off) - how do you know when you are done?

During the boil, how do you track the volume inside the pot?

Is this important anyways, or am I over thinking this?

It's pretty important, but it's pretty simple to measure volume inside the kettle. The measuring part is the easiest--you can mark your paddle or spoon with markings to let you know how many gallons you have. The first time you do this, take an old milk gallon, or your bottling bucket and pour in one gallon at a time, marking as you go.

The trickier part is determining how much water you need to sparge with, because it can vary based on your equipment. Start with a calculator, and eventually you'll get a handle for your equipment.

Bazaar said:

The trickier part is determining how much water you need to sparge with, because it can vary based on your equipment. Start with a calculator, and eventually you'll get a handle for your equipment.

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Not at all... the sparge amount will be exactly what you are short for your batch size.

Bazaar said:

It's pretty important, but it's pretty simple to measure volume inside the kettle. The measuring part is the easiest--you can mark your paddle or spoon with markings to let you know how many gallons you have. The first time you do this, take an old milk gallon, or your bottling bucket and pour in one gallon at a time, marking as you go.

The trickier part is determining how much water you need to sparge with, because it can vary based on your equipment. Start with a calculator, and eventually you'll get a handle for your equipment.

Click to expand...

hmm...my spoon is stainless steel, tough to mark. I wonder if I can find a stainless ruler marked off in inches, and use that to keep track of depth in the pot - then it's a simple inches/gallon conversion. Seems to me like that would have a better accuracy than marked delineations on the spoon.

I filed some notches in my paddle as mentioned above. Works like a charm. Whatever the difference in volume is between your first runnings and your pre boil target is how much you have to sparge with. My system is actually that calculation plus 1/2 gallon. Not sure why, but I always need to sparge with an extra half gallon.

Prior to getting kettles with sight glasses I used a metal ruler, which worked like a champ.

Learn early on what your boil off rate is, it's different for different setups, even the weather affects this. Wind and barometric pressure included. Time and trial run works best. I use a stainless brewpot, I usually try to start a 5 gallon batch with 6.5 to 7 gallon preboil. I took my angle grinder and made a slight indention inside the brew pot to mark my beginning mark and another lower for my ending mark. This is where I want to be for my beginning fermentation amount.
Another way is to slowly fill your brewpot with hot water slowly and measure different points. Not all brew pots are flat on the bottom (my pot is a converted keg and is concaved on the bottom) so simple geometry might not work. This will tell you how many gallons per inch in case you want to brew smaller batches.
But in answer to your question..yes it is pretty important.

╥R² x H ÷ 231

I learned many years ago, where you are has a huge impact on boil off (relative to humidity & ambient temp). either way, I marked my old boil spoon. it works great. I'm still trying to get a handle on AG, but boil volume is one less thing I have to worry about. thank you magic spoon!

I measured out all the volumes on my paddle for my kettle and used a dremmel to carve them into the wood. Bad pic but works.

dryboroughbrewing said:

Prior to getting kettles with sight glasses I used a metal ruler, which worked like a champ.

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Yep, retractable tape measure does the trick in my keggle. I found that 9.25" = 6.75 gal, and then every 1/4" equates to about 1 quart. YMMV

Adjust for thermal expansion. I find it is approximately 4% at mash temps, say 150 to 170F. That is about one quart for a 5 1/4 gallon batch. I think it is better to undershoot and need makeup water to hit the OG.

I measure depth with an aluminum yardstick, less than $5 at a big box store.

CastleHollow said:

Yep, retractable tape measure does the trick in my keggle. I found that 9.25" = 6.75 gal, and then every 1/4" equates to about 1 quart. YMMV

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This only works if your pot is 14 5/8" ID

iaefebs said:

This only works if your pot is 14 5/8" ID

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Yea, mine is actually a converted Coors bulged-wall keg. The volume varies a little at the bulge, I just had to measure quart by quart to get the height right at various volumes.

CastleHollow said:

Yea, mine is actually a converted Coors bulged-wall keg. The volume varies a little at the bulge, I just had to measure quart by quart to get the height right at various volumes.

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Ahh, that clears up your numbers better. the formula in post 8 only works for a flat bottom straight walled pot. I was wondering how you came up with your numbers. Kegs are a different matter with convex bottoms and bulges.

I've put sight glasses on both my HLT and Brew Kettle so I knew how much I had in there, glad I purchased them:

Site gauges on all 3 for me as well, calibrated at 1L increments. I put a cap with small holes drilled in it to keep any grain out.