I have a new Pentair 420 cart filter (upgrade from 15 year old Hayward sand). I noticed after a day I have to bleed about 2 seconds of air. Everything is air tight but i'm running a variable pump on low speed. Sometimes in the summer we got away for 1-2 weeks up to the cottage. Is there a way to automatically bleed air? Or is it always a manual activity with these things? Never had to worry about this with the old sand filter..