I've never messed with the valves on this pool since move-in about a year ago. Pool came with an auto vac that was always connected. Trying to SLAM but not moving as fast as I had hoped. My Hayward Vac needs repair so I have taken it out. It occurred to me I may not be sucking from the main drain and just the skimmer. Sweeping algae and it goes no where. See photo above. Looks like I am just pulling from the skimmer. When I try to move at what I think would be half way my pump goes dry and I lose prime and filter PSI. What am I missing? Am I doing it wrong? Guidance please.