So, I am still pretty new here and into the hobby, but it recently came to my attention that there seems to be some mystery surrounding the TRUE volume of certain carboys. I recently purchased the All In One Pump and thus phasing out all my Better Bottles to Glass (better handles the vacuum). I had a 6 gallon Better Bottle (PET/plastic carboy) that was completely topped off to within 2 inches of the bung. However
after racking to the new 6 gallon Italian glass carboy there was a TON of headspace (no sediment left behind or wine in tubing). I was infuriated that I just spent $150 on 3 new glass carboys and they were not truly 6 gallons. It took nearly a liter and a half of store bought wine to get up the to neck (1125 ml)!
After contacting another local store they recommended trying there chinese made glass carboys as they are supposedly truly 6 gallons. To my dismay, after a racking to these new carboys it came to the same height! I do realize that most glass carboys are sold as 23 liter, not 6 gallon, but 23 liters=6.076 gallon, but that .076 only equates to 287 ml. So why was I still 838 ml off?? Time for an answer. I figured they had to be inconsistencies in where the factories are considering full volume so I decided to do a side by side comparison to find out for sure.
Below are both carboys side by side with EXACTLY 6 gallons of water. It is clear there is a major difference.
Now indeed the glass carboy is measured as 23 liters not 6 gallons like the Better Bottle so I decided to add the extra .076 gallon or 287 ml to bring it to exactly 23 liters and we still end up with the level below. It too nearly another 750 ml for me to get it right up to the bottom of the neck.
I am not a big fan of the options. Spend more $$ on a store bought wine which I don't want effecting my batch and may not even be able to find from the same appalachian, dilute with water (slightly lowering ABV), using marbles to raise the level which is a lot of extra cleaning/sterilizing, or an air bladder such as the on VacuumPumpMan is developing. Just seems a bit annoying to me that these glass carboys are so far off. Hope this is somewhat useful to someone.