I've had an Intex sand filter and pump on my 18' above ground Intex for a few years now. Been working fine. This year, I'm having some issues where when the pump turns on, it's sucking air and the filter basket isn't filling with water fast enough. I have it on a timer, so I hate to have it run all day like that and potentially burn out the motor. The current fix is to backwash the filter. It seems to take a few seconds until the water starts to come out of the backwash, almost as if something is clogged and then shoots out. Once the backwash starts to come out, I can switch it back to filter and it works fine until the next time the pump turns off and back on. I've checked for clogs in the pipes and didn't find anything. Suggestions?