I keep getting a large vortex in skimmer causing the system to get air. Pool store is saying g that the system is pulling air from somewhere causing the vortex. I see no leaks visually. no water anywhere. 1.5 hp pump no variable quad cartridge filter system. The setup is about a3 months old. Pressure gauge used to read 15psi steadily and now its staying at 7 to 10 psi. With little water coming out of the air relief valve on top of te he filter tank to release air. Store clerk said that the tank may have a hair line crack causing the air to suck in. Wouldn't that mean the suction line could possible be sucking air somewhere? The filter tank always seems to have some air in it ...is that normal. Usually about 3 seconds worth when I crack the relief valve. Please help.