Hi all, brand new to this group, looking for any and all help! We have a 33 ft, 52 in above ground pool with a sand filter waterway pump. 1.5hp pump takes 150 pounds of sand. It's running at 18 or so psi and pumps great for about 2 hours, then we have a huge decrease in the water flow out and in. If we backwash it for 30 seconds, it'll work great again for 2-3 hours...we are just lost!