Problems with pool cleaner

Hello all,

I've had a pool now for about 10 years. For the past few years it has become very difficult to maintain. The main problem that we have been experiencing is that the cleaner (Kreepy Krauly) seems to stop working, or slows down to the point of hardly working. I recently replaced it with a generic version of the same thing and it too seemed to work well for awhile. I have had to adjust the main control valve (the one that controls the vacuum and the skimmer line) so that there is enough suction for the cleaner to work. I also found that if I hook a small length of the hose into the suction port in the skimmer that it works much better. i know that this is not correct though, as it is not meant to work in this way. i thought maybe the lines were plugged so I stopped by and bought a drain bladder and checked the lines for blockage. They seem clear, although i was hoping that a large bunch of leaves or something would come out to solve my problem. I also checked the impeller, which was pretty clean. I am at a loss as to what to do next. The chemical composition of my pool is good, but there is a large amount of debris on the bottom of my pool. I forgot to mention that my neighbors planted a tree right next to my pool on their side of the fence, and there are always quite a few leaves in my pool, which makes it even harder to maintain.