You mention that you Rinse and Backwash. If you do the rinse cycle BEFORE you backwash, this is an incorrect method. Also, be sure to always SHUT OFF the filter pump BEFORE you move and filter valves. So, when you want to backwash a sand filter, shut the power down, turn backwash valve to Backwash, turn pump on, Backwash for 1 minute or so. Shut power off, put filter valve on RINSE, turn power back on and run for 15-30:Seconds, shut power off, move valve back to filter position and turn the pump back on. What you are experiencing is very common with Sand filters. Be sure that you do NOT Backwash too often. You actually want the sand bed to get dirty. This filters water better. However, you Must Backwash when the pressure rises over 10 PSI after the filter is backwashed and cleaned. The best surefire method is to watch the flow out of the return closest to the filter. When the water is returning back into the pool with good velocity, the filter is clean. When the return flow slows dramatically, it is time to Backwash. Hope this helps.