When I close the valve to the skimmer and only use the main drain, the pump basket does not fill up and I'm getting quite a bit or air in the filter; I can purge the filter and come back 30 minutes later and air is in the filter. I do not have a separate valve for the main drain and skimmer; it's controlled with a Jandy 3-way valve.
If I open the skimmer valve completely and partially close the main drain, the pump basket fills and very little air is in the filter.
I've tightened the skimmer lid, pump ports but no change.
The suction plumbing is 1.5"; is the pump not getting enough water with only the main drain open?