Came across this forum page and needed to join. Can't find good answers with google alone. So I've bookmarked it and will visit often. Pool owner for over 8 years general contracted the build myself. My newest stupid problem was last night. Air bubble in the return. Finally this morning I should have "KISS", keep it simple stupid on troubleshooting. Last night I was purging the skimmer and drain lines for 2 hours only to find that my air bubbles were caused from the pump filter cover o-ring was shot! Lesson learned, to start with the simple stuff first!