Hi, I have a 1 hp Hayward power flo lx pump. I think it's not priming but I'm not sure. I fill the basket with water and turn the pump on. It clears the water out from the basket but then no water pumps through. I have it hooked up to a proline filter. I just changed the sand in the filter. I don't think that would have anything to do with this problem. I checked for leaks but really didn't see any. And the lid on this filter is a real ***** to loosen. So I believe it has a tight seal. Any ideas?