Depending on the use of the pool and the condition of the water. It is recommended to change the filter cartridge at least every two weeks. The condition of the cartridge should be checked weekly. You can prolong the life of the cartridge by cleaning it with a hose or by spraying out the dirt with centrifugal force. If the cartridge is still dirty, replace it immediately. If it has not been cleaned or replaced, it may cause a significant reduction in water flow and thus a reduction in the performance of the filtration process.