I have a Hayward 65 DE filter, a Hayward SP2615x20 with a 2 HP Century UST1202 pump. Opening up for the season the pump won't stay primed. If I empty the water from the filter the water flows in really quickly to the basket and primes but it quickly loses prime and lots of air bubbles. I have checked the lid, the drain plugs and pressure tested the lines. The lid maintains pressure if I turn it off, it has a seal and you can hear air escape. I switched to salt water 2 years ago and I replaced my pump 5 years ago. It sounds fine, not like the one I replaced with bad (loud) bearings. I didn't use the EasyKit for salt water - could that be it? Water is not coming out under the pump.
Could this be an impeller problem? I checked it by hand inside the basket and it appears clear and it moves with my finger spinning it. I spent most of the day checking skimmer lines, thinking maybe one or more cracked over winter, but they appear to be ok.