These filters come with an automatic backwash system. Depending on the amount of water you are sending through the filter you can program it to automatically backwash from once to several times a week. This backwashing assures the filter will stay clean and never begin to channel. Channeling is what occurs when a filter starts to plug up and the water begins to create a channel through the filter media. When this happens the water is exposed to only a fraction of the filtering media rather than flowing evenly through all the media thereby greatly reducing the filters efficiency.