I have a summer escapes above ground pool. I think it is 15' diameter. I'm not sure if the pump is working. I hear it running, but my pool gets nasty quickly regardless of adding chemicals. When I look in the pump, I see water around the filter, but not in the middle of the filter. No water is getting to the chlorine tablets in the center of the filter. I change the filter at least once or twice a week. Any suggestions for troubleshooting?