As is well known, the floor of this Chamber is inserted between the walls, thus creating a gap between the base of the Chamber walls and the sides of the floor .
Somewhere on the Internet are photos of the excavation underneath the north end of the sarcophagus (granite box, if preferred) and the area between that and the north wall of the Chamber.*
These photos reveal gaps between the limestone core blocks on which the granite flooring rests.
Any water entering the King’s Chamber would simply have drained down into the body of the Pyramid.
*it is not known who was responsible for this excavation, but the consensus is – so I believe - that it is the handiwork of Al Mamun (spelling?) and his motley crew.
p.s. I am one of those batty individuals who has the temerity to support the view that the Great Pyramid of Giza and other Egyptian pyramids are tombs.