I've read a lot about this problem but it's never quite my exact issue. Occasionally (not all the time), when my pump shuts off, water rushes out of the basket and into the pool (sometimes so forcefully that it bumps the skimmer cap off). This forceful rushing of water makes be believe there is pressure build up and not simply a leak allowing the water to flow back to the pool. This does not allow the pump to start up on its own as the prime is completely lost. This has only started after 2 months of troublefree operation. This happened last year as well. I get around this problem by, backwashing the filter, rinsing and setting it back to filter. After doing this, the pump basket will hold water without a problem. This trick works every time but I still run the risk of not catching the problem before it happens again.....and running the pump dry. So what is causing this??....air pressure trapped in the sand filer from a suction air leak? I imagined when backwashing, I am pushing all the air out of the filter, allowing the pump basket to hold water when shut off??? I don't have a air bleader on my Hayward sand filter. The mulitport valve appears to be leaking very slightly under the handle and I plan to change that out at the end of the year as it doesn't leak all the time. Yes, there are some small bubbles in the pump basket while operating. (something I might have to live with as it's an older inground pool with black poly and barb fittings on some of the junctions. Anyone who could shed some light on this intermittent problem is appreciated.