What's the full volume of "3 gallon" carboy?

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I’m making much better effort now to keep it all topped up with absolute minimal headspace even though I also use headspace eliminators on the carboys.
Big reason I'm not liking the new Big Mouth Blubbers for aging... too much head space in the big necks. had a couple batches get nasty bacteria on top. Hopping to save them with good 4x meta solution

I've racked from one 5 gallon carboy to another and had it overflow by a significant amount. They vary within an few % manufacturer to manufacturer.
I think it alos has to do with wall thickness of the glass

But liquid volume is not constant. It will change by temperature. So when you state that something holds 3 gallons at what temperature is that volume accurate? And does all liquid expand and contract at the same rate when heated or cooled?
No joke, I use to top mine right up to the bottom of the cork, or within a 1" of it. Not anymore. With heat they expand and will rise up into your airlock.
 
So if my previous post left you slightly confused.... perhaps this will finish the job.. :)

Reminds me of an SAT math question! Lol.

Carboy B is the largest
Carboys A&C about -6oz.
Carboy D is the runt at -10oz
Final answer!

I’ve got a 5gal that’s more than 5.3gal actual.
A 6.5 closer to 7
And I have x4 54L demi’s which vary but the real drag is one of em has a larger bunghole than the others requiring a different sized stopper. It is what it is tho. Fughetaboutit.

My LHBS supplier has their own direct glassmaker source. Take the good with the bad. Dirt cheap. But sizes tend to vary.
 
I agree AJMASSA - Makes my brain hurt figuring it out.
And now that runt Carboy 'D' is the next one I have to rack into in a few days. Going to be interesting as the remaining 3 gallon batches cycling through the racking process should have virtually no sediment other than a dusting on the bottom. Time to get my smaller 12, 16, and 20 oz containers cleaned and ready for use.
Before I rack again I'm going to do a real measurement of that carboy and I think I do have another spare that I should check as well.

Yeah the bung fits are a real headache too. I keep splitting the small plastic ones that are supposed to fit my screw-top 1 gallon / 4 liter carboys. Need to find smaller bungs for those. So far the ones I've tried are too large and pop back out.
 
Anyone know with some degree of accuracy what the volume of a "3 gallon" carboy is to the bottom of the spout? I'm fine with liters or gallons.

Alternatively, do you know the liter volume printed on the bottom of the "3 gallon" carboy and what height they are measured to on the carboy?

I have most of my different carboys graduated with volume markings but can't seem to find a 3G with markings.
I have three 6 gallon carboys and all three are different. What I did was put white electrical tape on the side of each of them and fill them a gallon at a time and mark the tape at each gallon poured. some people do etch the glass with markings.
 
Three gallons vs 3 gallons +18.75oz !!!
So it was a slow day for me, too nasty to do anything out side really - obviously a GOOD time to rack some wines on their 3 month cycle
AND I remembered to take the time to measure the volumes of each of 3 x 3gallon carboys. I filled each one to the same point - bottom of the fat ring on the neck. (See Image)I used an 8 cup plastic measuring bowl and of course it should have taken exactly 6 to get each one close to the top I would count the first as spot on for our wine making uses and the second acceptable but geet a look at number 3 !! [Oh Yeah I marked each on on the bottom for future reference and in this case Warning.]
1) Volume = 3 gallons .75 oz
2) Volume = 3 gallons 3 .75 oz
3) Volume = 3 gallons 18 .75 oz (Double checked that too)

The last one had squiggly lines on the bottom of it unlike the other two. Obviously 3 oz is no big deal but I was blown away by that third carboy volume.
Interestingly I checked and that equals a 402.750 ounces
11 liters = 387.145 oz
12 liters = 422.340 oz

Sort of at a loss on the best solution. Three gallons in the third carboy is well below the neck and has a surface about 7 - 8 inches across (Diameter) giving too much head space for aging.

I've got a total of 7 3 gallon carboys so I will have to measure and as I go through these I'll get them all checked out. 3-4 oz variance isn't a big deal. 7 ounces starts to create issues but this is crazy.

On the upside when I racked from that third carboy today I had enough clear, sediment free Black Currant wine that we will have two glasses of wine tonight. It's about 9 months old so this is a good point to sample.
 
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Not sure I see the problem. Carboys are for use after active fermentation has ended. Buckets are best for use when you are pitching the yeast. The idea then is not simply to aim for a specific volume (given the loss to lees etc when you rack) but to aim for a specific SG at a larger volume than will fill the carboy. Of course, if you are working with kits that may be an issue... but 6 gallons at bottling should (I would argue) always be 6 gallons PLUS at pitching, ditto 5 gallons, ditto 3 gallons and 1 gallon. The exact volume of your glass carboys is then not really an issue, is it, if you design your must to exceed the volume of the secondary?
 
The problem comes into play when racking from one carboy to another. If my current carboy is right at 3 gallons +/- a ounce and the one I'm racking it into is 3 gallons 18 ounces, that's a lot of volume to make up.
I rack every 3 months and unless I rack into one carboy, clean out the old and then rack back into that freshly cleaned "old" carboy their can be issues and it work both ways if the new carboy I rack into is a 3 gallon and the 'old' carboy is 3 gallons 18 ounces I'm going to to find another small container to put that excess wine into and airlock it.

Often I have 6 of my 7 Three gallon carboys filled with wine I'm aging. When it' time to rack them all I rack into the one unused carboy, clean-out the now empty one and tack the next carboy of wine into the freshly cleaned carboy and repeat that process until all the wine has been racked and dosed again with k-Meta. When the sizes vary so much it make it very difficult to keep track of the volumes of each carboy. If only one carboy is extra large I could rack into it, clean the now empty carboy and then rack again back into it but that's extra work and extra exposure of the wine to potential oxidation.
 
I have 3 glass six gallon carboys, they differ just as wildly as you have found for your threes. I am now collecting PET carboys, as the glass is too dangerous to deal with. Also consistent in size, but still much more than the labeled volume.
Almost half a gallon more fits in my five and six gallon better bottles.
 
I have 3 glass six gallon carboys, they differ just as wildly as you have found for your threes. I am now collecting PET carboys, as the glass is too dangerous to deal with. Also consistent in size, but still much more than the labeled volume.
Almost half a gallon more fits in my five and six gallon better bottles.
I

Yep! I have several Better Bottle 6 gal. carboys as well as a couple of Vintage Shop carboys. Every one of them holds a different volume. The problem comes up when you rack from a "low volume" carboy into one with a significantly higher volume. You wind up with the wine level well below the neck of the carboy and way too much exposure to air.
 
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