Hi, I have had my pool for almost 2 years and I noticed the cartridge needs to be cleaned frequently, sometimes more than once a month. After a year, I brought a new cartridge and it didn't need to be cleaned for 2 months, but after the 1st cleaning, it needed to be cleaned again 3 weeks later. What I noticed is the after I clean it, a lot of dirt gets struck in the grooves and no matter how hard I try to clean the dirt inbetween the grooves, its hard to get out.