Our icebox drains into a deep narrow container. There is a float switch at the top, and one at the bottom. They are wired via a latching circuit so that the
pump does not come on until the container is full, and pumps until it is empty.
Also, remember that the icebox drain should have a 'U' in it, so that there is a waterblock to stop the cool air from draining from the icebox.
Regards, Richard.