I have a lot of trees and bugs. They breakdown on the bottom, I vaccuum them up and they come right back out through the jet. I cleaned the filter before vacuuming and after. Also the housing the filter sits in has some of the small stuff in the bottom when I pull out the cartridge...I had thus problem last year and we concluded the filter housing wasn't tightened enough. Now I have no clue and it's annoying vacuuming what I already vaccuumed!