This is my first time closing a pool for the winter. I have a 48x28 above ground with a main center drain. Closing the drain attached to the skimmer is pretty straight forward. It is the center drain that i have some concerns with. The drain that connects to the pump comes out of the ground next to the filter. One end extends above the water level about 1ft that pipe is split and has a union that connects to the pump. I have heard several methods to close the center drain ranging from chemicals to pumping the pipe dry. I was wondering what is the simplest but effective way to winterize a main center drain. I attached a picture of what the setup looks like. This is from the original filter which i have since replaced. However the basic pluming is still there just a little cleaner.