No you don't always get contractions when your waters break. With me I was niggling for a few hours (but not having contractions) once my water broke it was bang 2minutely contractions (only last 20sec to start with)
As a midwife usually contractions follow (especially if you have had a baby vaginally before) within a few hours of your waters breaking if not before. But we augment (speed up labour) many women because they have broken their waters but haven't gone into labour. Augment is like an induction but the difference is labour has already started like water's ruptured or contractions etc.