Same problem, brand new filter... I'm 190 lb guy who works out 6 days a week, I can't open this filter for the life of me. If I knew it would be so hard to open I'd have opted for a less expensive sand filter. Cartridge are supposed to keep the water clearer but if you can't open the filter to clean it without spraining a wrist or having a heart attack (or both) what good is it? Beyond mad, I'm thinking of just biting the bullet next spring and buying a filter that actually opens. Even the brand new Hayward chlorinator didn't work properly this past summer, i,thought they were supposed to be good products, dealing with their customer service is pointless.