My main drain isn't working. I have no idea why. I just moved into this house and found the pool half empty and full of leaves. It had a cover on it that was well fitted so i'm not sure how the leaves got in there. Anyway...I've cleaned and filled the pool. My levels are almost perfect but there's still a little green in the deep end. I couldn't figure out why until I turned the valve of the skimmer and nothing went into the pump. I've tried priming it, I've looked for cut-off valves separate from the main one that is next to the skimmer one, and I checked the actual skimmer to see if it was one of those I've heard of that connects within the skimmer. Nothing. I'm at a total loss. Any ideas?