I have a 5 gal. corny full of ginger ale. It has slices of fresh ginger in the keg (cut into stick shapes large enough to not be able to plug the downtube).
It has a 4 foot (short) cobra tap on it. I de-pressurized the keg for serving and set the reg at 1psi, held the tap at chest level and poured with a *GUSH!* It was as if I poured at 20psi.
I checked my reg, hit the relief valve again, re-checked the reg, and poured again with the same result, high-volume foamy beer.
Then I disconnected the gas-in, de-pressurized the keg again--this time causing foam to shoot out of the relief valve. I can leave the gas-in off the keg, and hit the relief valve every few moments with a release of gas I would usually get while pressurizing at ~15psi . . . .
. . . so somehow, it is still producing gas. Fermentation is the obvious answer, but doesn't make sense--the beer finished at 1.011, has been in the keggerator for about 3 weeks now (40 degrees F), and I don't detect any off flavors or contamination (it's delicious).
Could the ginger be causing gas to come out of suspension somehow? I've used fresh ginger in the keg before and have never seen this happen . . . very odd.