Winterizing the the pool this week and was wondering if I have to put a cover over the skimmer opening? I put in the black bottle plug thing and cover up the hole in the skimmer top lid but wasn't sure I needed to do the other. Had a gal talk about a skimmer plug that covered the whole thing that she had purchased this summer for winterizing. I was told I didn't need to cover it and to keep a plug in the skimmer collection unit and that is it. Thoughts?