23 litre mark on carboy?

Just a quick question, I have a standard glass carboy, looks just like every other modern carboy out there. I think I added too much water making by brew, just wondering where the 23 litre mark is? I guessed it to be where the carboy starts bottle necking up. Anyone?

No marking, you gotta figure it out yourself and mark it.

On mine, there's a small bump (that you have to look at almost at an angle to see) just above where the bottle starts to taper up to the neck. It's at the top of that bump on mine. I have the measurements written down at home (I measured with a tape measure from the table up to 1, 2, 3 gallons and so on). But, it may be different on different carboys.

What I did was pour a gallon in, mark it, pour another in, and so on. My only problem is that the permanent marker rubs off somewhat when cleaning/handling, and I have to reapply it which gets annoying. (one of the reasons I measured! - so I wouldn't have to do the time-taking, pour-and-mark method again!)

I was having the same issues on marking a glass carboy and getting knowing my final amount of home brewed goodness. Here's what I did... Pour 1 gal (or whichever units you prefer) of water into the carboy and mark with masking tape. Repeat 5 more times (for a 6.5 gal). Pour out the water, lay the carboy on it's side, and add some glass etching paste to the taped markings. Let sit for 10 mins (I believe) and rinse thoroughly with water.

I now have nice permanent markings on my carboys. I did this to all 4 of them. The glass etching paste isn't the easiest to find, I had to go to a few hobby stores to find it, but well worth the cost and time...I think.