Newbie here so be gentle.
Pool is at proper water level and the skimmer isn't sucking air but I'm getting air in my pump basket and cartridge filter. So far I've replaced the O ring on the pump basket lid and the O rings on the Jandy 3-way spa diverter valve leading up to it. I lubed the new O rings with Magic Lube when I installed them. I've also removed, inspected, lubed (but NOT replaced) both the pump and pump basket drain plugs.
The pump is a Whisperflo two-speed pump and the odd thing is that it only tends to accumulate air in the system (top of strainer pot and filter) when running on the low setting which shows 7 psi on the filter gauge. High (20 psi) does not accumulate air.
My setup also has three 90 degree Praher ball valves prior to the Jandy valve on the low pressure side of the pump coming from the skimmer, main drains, and cleaner. All are tight now but I can't get to the guts of them without cutting PVC pipes first. Turning any one of these three valves off seems to have no effect on the small amount of air being drawn into the system.
I'm completely stumped as to why I would be drawing air into the system only when the pump runs on low. I'm also stumped as to where the air is coming from. I let the air out of the filter daily and it hasn't yet gotten to the point where it's coming out a pool return but it does accumulate a significant amount in the filter. Ideas? I feel like an auto mechanic just replacing parts to see if it solves a problem.
The attached picture shows my suction side setup. The pump basket typically contains more air than shown in the picture. I had just turned it off of high a couple minutes before I took the picture.