I vacuumed my old pool the other day. Now I cant get the pump to maintain prime , it seems to surge. It almost fills the pump pot , then bang , it's empty. And there is no pressure in the DE filter . As the pump fills with water it surges, almost fills then seems to shoot the contents of the basket, pump pot to the filter , air comes out the bleed valve, then it seems to suck back in. I don't believe that there are any suction leaks or clogged lines. I did find some things in the impeller but clean now! When I turn the pump off and attempt to open the lid it is in a vacuum. Next step is to inspect the Hayward Multiport valve and inside the DE filter.The return lines just keep pumping lots of air in the pool . Any other ideas would be appreciated. Thanks !!!!!