I just noticed that, if I have the diverter completely to the main drain (a dual), the pressure reading on the top of my filter is about 15. As soon as I open it even one tick to allow the skimmer (and all the way until it is just skimmer), the pressure reading is about 20. I also noticed that the pump basket doesn't seem to fill as much when it's completely on the drain.
Should that be like that? And, if not, what might be making it do that? It almost seems like there's a clog or something in the main drain or line... (but I'm still pretty ignorant about all this stuff...)