During my (3) 3 oz pour experiment, there was no sediment that I noticed. The only sediment I ever had was in the very first 8 oz pour that I dumped.
I'm thinking maybe the 1 oz of beer in the line was enough to make that first 3 oz sample have a nasty metallic flavor. Then the second pour basically rinsed out some of that residue still in the line, which is why the metallic flavor was very subtle in that one. Then the 3rd sample tasted normal.
Does this make sense or do you think it could be something else? I'm stumped because that 3rd 3 oz pour matched the flavor profile of my bottled version.
I think this is right. It is pretty easy to test - get yourself a picnic tap and some line, hook it up and pour three samples. Then hook it back up to the kegerator and do the three samples again. Do them in that order.
If the picnic tap samples taste bad, it is in the keg/dip tube. If they taste great, it is not there.
If the picnic tap samples taste fine but the kegerator samples are bad, it is between the keg and the faucet.
If all of the samples are good it was somewhere in the system but would appear to be gone by now.
Even if it is not caused by microbial contamination, there could be exposed metal somewhere that is causing the off flavor.