That's a theory that seems to fit the facts.
Originally Posted by Yooper
No, overcarbing does make a beer flat. Weird, I know.
But what happens is the co2 is "knocked" out of solution on the way to the tap. That makes a big foamy head (or a whole glass of foam) that is comprised of co2. When the foam dies down, the underlying beer is lacking the co2 due to it coming out of the beer during dispensing (creating the foam). In that case, a flat tasting and feeling beer is indeed due to overcarbonation and serving with a line unable to handle that carb level (ie lines too short for that carbonation level).
I know I said that the PSI was set at 10 PSI, but in reality, it was set at 10 PSI for 10 days (it was totally flat) and then for 2 days I jacked it up to 15 PSI, and then turned it back down to 10 PSI. I didn't shake or rock the keg.
Looking at the graph below from the sticky in the kegging forum, maybe the carbonation was traveling up like the green line, I turned it up to 15, causing a jump in the volumes of carbonation (red line), but the overcarbing didn't really kick in until the 9th glass? The 1st 8 glasses had perfect head (1 to 1.5 inches) and perfect carbonation and good taste. The 9th glass had tons of head (2.5-3 inches) and perfect carbonation. The 11th glass had tons of head (3-4 inches) and not enough bubbles.
The next morning the 1st glass tasted good again, but then the 2nd was flat and acidic tasting again and it never got better after that.
So if the beer lines were pulling carbonation out of the beer before it hits the glass, then by the time I thought the keg was ready for drinking, it was nearly overcarbed and then became overcarbed in the next few hours? I was also shooting for 3.0 carbonation (for a Belgian Wheat) but that may be a mistake. I should shoot for 2.0 until I can get this right.
That makes sense, since the keg was not leaking and the diptube and connections were all completely clean.