Check whether the cartridges are done

Cartridges do not last forever There is no manufacturer-stated replacement interval for these — they are replaced on condition. Once a year, look at them properly while they are out for a clean. ## What ends a cartridge - Pleats permanently flattened or splayed, so the media no longer stands up - Fibres visibly shredding or fuzzing - A cracked or distorted end cap - Pressure that climbs back up almost immediately after a full deep clean ## When you do replace them Replace all of them at once. A mixed set filters unevenly, and the new cartridges take the whole load while the old ones pass dirt through.