I installed a new multiport valve and new pvc today, and changed out my sand (it was awful even after trying a deep clean). When I got the pool filled up enough, I turned it to backwash and turned pump on and it backwashed just fine. Then I switched it to rinse, turned the pump on and got a humming noise and no suction. I did this about 5 times, and still no pump power, just humming. I turned the multiport to filter, and tried to power the pump again, and still humming. Any suggestions? I got the pool fever and can't get it going!!