Hi Lily, The American is here :-) They are interchangeable, however we see "tap" as slang for faucet. So, I suspect in a medical setting it would be "faucet". Have a great day, Stephen

In British English we only use 'tap', it doesn't matter what kind of tap it is. You'll have to wait for an American English speaker to confirm how it is elsewhere. I know 'faucet' is normally preferred. I doubt they make a distinction like you suggest in your question.