We purchased a 16' Ultra Frame Pool by Intex last year and everything worked great! This year we put it back up and then I noticed when we turn the pump on it has great water pressure and moves the water around but after maybe 30 minutes to an hour the pressure drops tremendously and the water isn't moving around well. I have looked through the manual and scoured the internet for a solution and have found nothing. Put a brand new filter cartridge in and within that same time frame the pressure dropped, checked all hoses for leaks/clogs/etc, used the air release valve as well. I can turn the pump off and pull the filter cartridge out and then put it back in and it runs great again for a short time and then it goes right back. Any suggestions?? I can't get customer service to answer and I am loosing my mind over this!!!!