The filter screens out solid particles, debris, insects etc. found in the circulating water in order to ensure that it stays clean and clear. There are several technologies:
The sand filter: this is the most common filter. Water travels through a bed of sand that screens out suspended particles. Its filtration fineness level is not high, between 40 and 50 microns. However, its performance can be improved by adding chemical products such as flocculating agents or by using other filtering media such as zeolite or ground glass. It is simple to maintain but it consumes a large amount of water sourced from the pool.
The cartridge filter: it has the advantage of a good filtration level of between 20 and 25 microns. Compact, it is ideally suited to cramped locations and avoids the need to discharge chlorinated water which is increasingly being regulated. To clean this filter, just remove the cartridge and play a water jet over it, using small amounts of tap water.
The high capacity element filter: because of its size, this cartridge filter will screen out a lot of debris and only has to be cleaned once or twice per season. It uses less water but requires more space. Having a filtration level equal to that of the standard cartridge filter, between 20 and 25 microns, it constitutes the best compromise between water quality and maintenance.
D.E. filters: the last word in filters. Its exceptional filtration of between 3 and 5 microns - diatom is an extremely fine powder made up of the skeletons of aquatic micro-organisms - provides an unparalleled quality of water which also allows you to reduce your use of treatment products. It is by far the most efficient of the filters but requires a little more by way of maintenance. Indeed, a separator tank has to be installed to filter the water used to clean the diatom filter and this water must not be discharged into the natural environment.