Your skimmer should have come with a flying-saucer-looking device called a float valve. It sits in the bottom of the skimmer, covering the two holes creating a suction at the bottom drain port. If you want the bottom drain to work, you need to adjust the small teardrop-shaped flap to cover about half the hole in the bottom of the float-valve. If there is a hose connector in the suction port of the skimmer it will have to be removed for the device to fit properly.