The pool water must be filtered, otherwise it is not crystal clear soon, but dirty cloudy. Dust and pollen falling on the water surface, swimmers bring skin and cosmetic fats into the water as well as hair and skin flakes or blades of grass stuck to his feet. All these substances must be filtered out of the water. In a sand filter, a pump draws water from the pool, it pushes through different levels of sand layer in the proper filter and back into the pool. The sand layer consists of quartz sand. The individual grains are not round like the river sand from the sandpit, but sharp, uneven and full of tips. (Consider again a few grains under the microscope at 10x or 20x Vergrössung.)
It is also possible instead of quartz sand filling using an AFM (activated filter material). It is a revolution in the filter area, since the filter material made from recycled glass is obtained. Because the glass is processed, it is not normal glass recycling. This gives it high adsorption forces, as well as catalytic and oxidizing properties.
In both versions, a pump draws water from the pool, it pushes through different levels of AFM / sand layer in the proper filter and back into the pool.
Dust, grease and other impurities remain at the tips of the sand grains hang and the filtered water leaves again clean the boiler.
In one or max. two weeks to collect as many impurities in the filter bed that only the AFM / sand filling needs to be cleaned. The filter should be backwashed.