Concrete in ground pool: Jandy 1.5 HP variable speed pump: 60 sq. ft. Jandy DE filter. Just cleaned filter. Upon restarting pump, pool flow is very low. Pump is not drawing water from pool strongly. Filter basket is only half full of water. Opened two valves and cannot see any blockage. Tested flow by alternating from skimmer basket and vacuum line. No change. Operating pump on manual only. Pump sounds okay. Filter pressure is 14. Have not replaced DE yet before I figure out the problem. Any suggestions on where to look for a blockage, leak or pump not operating correctly.