"The whole point is for everybody to pick it up and go, 'I'd like to thank my son and my dad' - and you can always tell when someone has, because they're in there a little bit longer after they flushed," she said.
"They'll come out looking slightly pink-cheeked. It's hysterical."
Winslet, 39, said she feels proud not to reveal much about her failed marriages to Jim Threapleton (1998-2001) and Sam Mendes (2003-11).
"No one really knows what has happened in my life. No one really knows why my first marriage didn't last; no one knows why my second didn't. And I'm proud of those silences.
