pass urine/water

Around here a child will say, "I want to pee." In general people don't say they want to pass urine or water.

No.

Kids around here say "go peepee". Adults say something like "go to the bathroom" or with friends " I need to take a piss" (colloquial and slightly vulgar).

The term "pass urine" is only used in a doctor's office.

They're both quite archaic, they're not terms anyone under the age of 75 is likely to use. Going to the bathroom, is a phrase that only Americans use, we say Go to the toilet or lavatory. The most common term in the UK is having a wee.

There are other colloquial, vulgar terms, too many to go into.

Those are very outdated.

If I'm in a setting where I don't know the other people well but need to use the washroom I say: Excuse me, I'll be back in a moment.

With friends it's different: omg I HAVE to pee!