I still think a photo might help.
Buck seems to have using his unit long enough for the anti-freeze to have flushed out but maybe it is some residual trapped somewhere? It's also present in hot and cold water.
By description, I'm thinking it sounds more like dissolved air (or a gas) in the water being released since there doesn't seem to be foam and froth sitting on the surface and goes away if left to sit. It causes "twinking" in his nose which is similar to a carbonated beverage. It sounds like it has an odor, but is it a foul odor or something that isn't too bad? What does it smell like?
Some causes of air in water:
New Hampshire Dept. of Environmental ServicesAir can be trapped in water from wells as in water in Tuscon for example:
City of Tuscon waterWe have 4 stage water filtration and the last filter is a very low micron rating 10" whole house ultrafiltration cartridge that supplies a dedicated RO type faucet. It doesn't matter where we are, with all water sources, the ultrafiltration filter causes dissolved air to be released. It looks very cloudy at first and after a minute or so, it's perfectly clear. I have no idea yet why it's just the UF filter that does this. This does show though, that dissolved air in water is common.
