When we went to our birthing classes, which were conducted by the hospital, we were told to call the hospital when my waters broke to let them know. I did this and was told to come on in because there was a bit of yellow on the pad. If there hadn't been any, they would have waited a lot longer before I went in - and my contractions hadn't started at that point.
Perhaps contact the hospital you're booked in for and see what there preference is?