Am I right to say that it if not rude to ask "Are you passing water or defecating?" if I want to use the toilet and someone is inside. I mean I want to know whether I have to wait a long or short time.
I agree - the only people 'licensed' to discuss your bathroom activities would be family members and your doctor... The discussion of how one would behave in a public lavatory belongs in the Cultural discussions forum.Well, 'defecate' is a reasonably polite term, but I would find it rude if someone asked me this question regardless of which words for defecation and urination they used. I agree that "Will you be long?" is infinitely more polite than referring to what you will be doing specifically. (Though, asking about this in the first place sounds kind of rude. They'll take as long as they need to, and it's none of anyone else's business.)
The intent behind the original question is genuine. In circumstances where the facilities are limited and within a family (as Elaine Koh has explained) the need for this kind of question is very real - and in my family it was not at all surprising for someone to knock on the door and ask "Will you be long?" We had our own "code" for responses and the rest of the dialogue.It is probably just as well if you don't find an English translation - it is definitely not a question you should ever ask a native English speaker.