I've been using a converted chest freezer for nearly a year now for storing and dispensing from corny kegs and for lagering. Depending on whether I have kegs of homebrew, I may have a sanke keg of commercial brew.
I just added two pieces of equipment to the system: a one-to-three gas manifold and a second sanke tap and hooked up two sixth barrel kegs from the same brewery. There was a large discrepancy in how the two kegs dispensed -- one was slow, as if there was almost no pressure; the other was way too pressurized and foamy.
When I adjust gas settings at all -- change pressure on the regulator, bleed gas with pressure relief valve, etc. -- the system hums like a harmonica. This may have come from one of the pressure relief valves (on the sanke tap or on the manifold) and seemed to be a red flag. I have not been able to detect any leaks. Upon visual inspection, everything seems fine as well.
My question is this: Why would these two identical kegs fitted with identical taps filled with beer from the same brewery dispense so dramatically differently? Does one tap have a defective pressure relief valve?
Secondly, a big BBQ party drained both kegs in a day, so I didn't have much time to troubleshoot. How can I further test this if both kegs are blown?