We have a 18' by 4' Intex FrameSet pool and we run it about 20 hours a day. Running the pump four or five hours just doesn't keep it clean. With a smaller pool, you probably wouldn't need to run it that much, but I'd still run it longer than the instructions say to. After we had an algae problem, the guy at the pool store told us to run the pump 24 hours a day.