I just topped off my pool, inserted the plugs, attached the backwash hose, turned sand filter to Filtration, filled the pump filter with water and turned on the pump - nothing is happening. It is definitely working, but I am afraid i will burn up my pump if I let it run too long. I have turned the pump on twice and let the pump run two minutes each time, but nothing is happening - no water coming into the pump filter. Am I just too anxious? Do I need to let it run longer?