Skimmer (spa)
A skimmer or surface separator  (separates a substance from the surface of a liquid), is an essential accessory for the maintenance and cleaning of the water in a swimming pool . It is used  to remove all the surface dirt floating on the water surface, such as leaves, tanning oil and human secretions. These impurities remain suspended on the surface, affect the appearance of the water and are not always removed by the conventional vacuuming process. The skimmer is installed directly in the surface water suction system and also has the function of controlling the water level to prevent accidental overflows.  In the United States and Portugal, the use of skimmers in the construction of swimming pools is mandatory, regulated and standardized by competent bodies.