I have been curious about the way my pool was designed due to an issue I have from time to time. I have three skimmers. Two of the skimmers are tied to a water feature and run off one pump. The other skimmer and bottom drains (2) are tied to my second pump. The issue is that when the water level drops to about 1/3 of the way up the tiles the pump that is tied to the water feature starts to suck air. Is this expected? Is there something I can do aside from adding an auto fill that would help?