Cartridge filtration is a type of mechanical cleaning for swimming pool water that uses a cylindrical insert, known as a 'cartridge'. It is most often made from special pleated paper or non-woven fabric and acts as a fine sieve. A pool pump circulates water through this insert, where mechanical impurities such as hair, insects, or small skin particles are trapped. For proper function, the cartridge must be regularly inspected, cleaned with a stream of water, and after a certain period, when it is too clogged or damaged, completely replaced with a new one. This filtration principle is common in smaller above-ground pools and hot tubs.