Infinity pool

An infinity edge pool (also named negative edge, zero edge, "disappearing edge," or vanishing edge pool) is a swimming pool which produces a visual effect of water extending to the horizon, vanishing, or extending to "infinity". These style pools are often very expensive and require extensive architectural design.

Since these pools are almost always built in precarious locations (cliffs, mountain tops, beach front, etc.), sound structural engineering is paramount. The structural engineering must be based upon the geological conditions found on the site. A geotechnical report should always be commissioned, prior to the commencement of the structural engineering. The exorbitant costs of these pools is often found in the foundation systems that anchor them to the hillsides.

In reality the edge of the pool terminates in a weir that is one-half to one inch (12 mm to 25 mm) lower than the required median pool water level. A trough or catch basin is constructed below the weir. The water spills into the catch basin, from where it is then pumped back into the pool. The effect is particularly impressive where the infinity edge appears to merge with a larger body of water such as the ocean, with the sky (if the pool is located on the side of a hill or mountain), or with foliage.

Properly built, these pools have two circulation systems. The first functions just like a regular pool, filtering and heating the water in the main pool. The second circulation system (known as the "edge system" or "effects system"), filters the water in the catch basin and returns it to the upper pool. When the edge-system stops, the water level in the upper pool continues to spill into the basin - stopping at the level of the weir wall. The water necessary to raise the upper pool and fill the edge-system plumbing is called the "water in transit." Considerable skill is required on the part of the designer to incorporate a catch basin of an appropriate size.

If it is too small, swimmers will force out ("bather displacement") more water than the catch basin can hold. This can lead to catastrophic landslides or hillside erosion. Additionally, if the basin is too large, the edge-system pump may also draw down the catch basins' level, before the water has returned in sufficient quantity for the edge pump to retain its prime. The catch basin also needs to have additional holding capacity (above its static level - known as "freeboard"). The freeboard is the available extra capacity to hold the bather displacement and rain water, before it reaches the level of the overflow line.

Dedicated filtration systems are required on both systems. The edge pump is usually a much larger pump, required to overcome bather displacement, water in transit, and to raise the upper pool's level. It would be a waste of energy to run such a large pump as a primary filtration system. Adequate filtration is required on the edge-system (based upon the edge-system flow rate), as most of the debris flows over the weir and into the catch basin. A smaller circulation pump can be used for daily filtration on the main pool.

Failure to install filtration on the edge-system will result in the debris in the basin being blown back into the upper pool.

An automatic fill device should be incorporated into the catch basin. Electronic autofill sensors are preferred by the leading designers, as they have a built-in delay to compensate for wave action from bather surges. A common toilet cistern refill device should not be utilized, as they constantly bob up & down, causing annoying hissing sounds & water hammering in the nearby residence.

Infinity edge pools were the beginning of the mainstream trend to create architectural swimming pools, elevating swimming pools to an art form. From this trend, a new breed of designer was born: the aquatic designer, aquatic architect, watershape designer or watershaper.

Architects & landscape architects frequently consult with experts in this field, to create the magnificent pools seen at exotic resorts, exclusive estates, and on magazine cover shots.