After just pulling a sand filter and replacing it with a cartridge I am going to call B.S. on never having to replace the sand. The filter was a mess, cake all caked up and the sand partials were like tiny rounded off beads. I tried several times to clean the sand filter by soaking it in a cleaning agent to break down the biomatter then backwash (so much wasted water). Also had one heck of a time trying to keep the water crystal clear. The new cartridge is amazing and no more backwashing/dumping hundreds of gallons of chlorinated water.