I've noticed that my filter pot next to the pump will slowly fill up with air while the system is set on filter. If I switch the system over to recirculation the air will purge out. Switch back to filter and it will slowly gain air again. What options should I look into to figuring out where my leak is coming from? Could this be a worn/faulty spider gasket in the pump selector? Anything else to check out before I call someone in? Thank you.