The edge is a carefully controlled spillway
An infinity pool’s disappearing edge works because the water surface is held almost exactly level with a lowered lip. As water crosses that lip, gravity carries it into a narrow channel built just beyond the visible edge. From the pool, the channel is hidden; from below, it may be concealed behind the wall or structure.
That channel leads to a larger holding space, often called a surge tank. It gives the system somewhere to put water when swimmers enter, waves reach the edge, or wind pushes water across it. Without that extra capacity, the overflow could fluctuate or the tank could run dry when displaced water returns to the pool.
A loop that keeps the edge steady
Pumps draw water from the holding space and send it through the pool’s treatment equipment before returning it. Filters remove particles; disinfectants help control microorganisms. The return flow also helps keep the water circulating rather than letting it sit in the basin.
The engineering has to balance two demands: move water quickly enough to maintain the smooth, continuous overflow, but not so quickly that the system becomes wasteful or unstable. The pool’s level, the channel, the tank, and the pumps all work together. The vanishing edge is not an open drain; it is the visible end of a circulation system.
