Depending on the pump it may be easy to check/clean the impeller. I recently had an oak tree drop lots of stuff into the pool and it got by both baskets. The tree droppings look like worms when wet, pollen pods for lack of a better term, clogged the impeller. On my pump (Duraglass) it's easy to get to the impeller and clean it out. It isn't hard to do, but you need to separate the motor from the housing to get access to the impeller. The impeller is connected to the motor shaft.