Overflow Type Swimming Pools
A perimeter-overflow pool is a type of vanishing-edge pool designed so that water spills over all four walls, thus giving it the glazed appearance of a mirror.
To create this effect, the tops of all four walls are set lower than normal, so they sit slightly below water level. This way, water spills over the entire perimeter and into a containment vessel, from which water is recirculated back into the pool.
These pools often are set at ground level, with water dropping through a slot or grate and into underground gutters. A simple slot in the decking has become more popular, because it barely affects the appearance of the deck.