take a leak informal
have a leak informal

Or else went into one of them to take a leak.

Guy had to take a leak, and he picked here to do it.

I knew he was just going to take a leak.

To top it all off, why not take a leak on a piece of world history?

One thing came clear to him, though: he had to take a leak.

One guy taking a leak against a rock, we want to know about it.

I'd let him hold the last air bottle while I took a leak.

At least you can read a book or get up and walk around, take a leak.

It was just as well she'd already taken a leak.

"Where would somebody go to take a leak around here?"