In-Ground. My intake setup is all manual with 3 total valves. There is a primary selector that balances between what I'll call Side A and Side B. Side A is a 2.5" intake that goes to the skimmer on the far end. Side B goes to a second set of valves that lets me balance between the near side skimmer, the suction bottom cleaner, and the two bottom drains.
I just started getting suction loss. I eliminated all the obstructions and assured high water levels per usual, and then started to do some selective research. It appears now to be very simple. If I so much as crack open Side A, the pump completely loses suction and will not recover. If I leave Side A closed off, the system functions properly.
Is there a probable cause for that sort of sudden and overwhelming suction loss?