The air pocket is definitely increasing, as I need to bleed the air daily from the filter.
The pool company checked the pressure between the two surface skimmers and suction inlet in the strainer area. They said they did not need to check the main drain since it connected to a surface skimmer before running back to the pump (I asked twice). No pressure loss was detected. The technician noted that all was fine, and they didn't believe their was a problem.
I did look at the lid, but it appeared recessed and out of reach. I'll take another look at it. I'll also give the shaving cream around the drain plug and strainer lid a try to see if anything shows up.
I did not notice a vortex in either of the two surface skimmers.
Thanks for the help!
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