The swimming zone is the area intended for swimming that resembles a conventional swimming pool or pond.
The regeneration zone consists of a lined overflow pool filled with specific filtration substrate and flora. Plants used for water regeneration can be supplemented with decorative flowering species to create an attractive water garden environment. The biological processes that clean the water take place in this zone.
The swimming zone should be physically separated from the regeneration and should reach a depth of 2 m (6 ft 6 in) in swimming ponds. The regeneration zone and swimming zone must be equal in area for sufficient purification. The swimming portion of the pool can look like a conventional swimming pool or a natural pond. The regeneration zone can be placed adjacent to the swimming area or in a remote location depending on the space available. In modern natural swimming pools there is no minimum depth for the swimming zone and the regeneration zone can now be reduced greatly and in some cases is non existent. Clear Water Revival was the first company to build indoor natural swimming pools in the UK. In these pools a regeneration zone can be used outside the building or a natural filtration chamber can be built without a planted area indoors.
In an NSP, swimming pool water flows via gravity from the swimming pool into distribution shafts. The water then passes through a biological fine filter/bioreactor before it is pumped into the regeneration zone. Plants in the regeneration zone are planted in the substrate, and these plants compete for nutrients that would feed algae. The water is cleaned biologically by the metabolic processes found in the substrate in which the plants are rooted. Thus, microorganisms and the water plants ensure effective, continuous cleaning. No processes beyond these, such as UV sterilization, are found in true European style NSPs.
Because of their reliance on natural environmental factors, each NSP system is built with consideration to the region and climate where it is installed. Construction elements such as the biological filter and the combination of contaminant ridding plants vary with each pool.