I just opened my pool, and there is a lot of debris on the bottom. It looks to be too much for the Polaris alone. I was thinking about vacumming the pool and then cleaning the cartridges. I am not sure of the correct valve settings. Should I close off the pool drain completely? Should I also close off one of the skimmers? I don't want to burn out the pump, and I wasn't sure if I needed to leave the drain partially open. I don't know if it matters, but my equipment is below the pool level. I never have to "prime the pump," because as soon as the drain valves are open, the water starts flowing. I appreciate any suggestions.