Interesting thread. We are in the same boat! We've had ours 6 years as well. The gauge is busted as well, but like you, I know my pool and when to backwash, etc...

My problem is this: Last year my husband changed the sand in the filter - he's done that before (we've been AG pool owners for over a decade), but for some reason something wasn't right and sand was being injected *into* the pool. Not much - you couldn't really *see* it or feel it coming out, but I knew it was there because it would settle on the bottom and was VERY difficult to clean up (maybe too heavy or dense to be be picked up by the vacuum well?)...drove me nuts all year!! So I asked him today to take it apart and see what's up - he responded that it's a pretty simply operation and he can't imagine what caused that and maybe we need a new filter? (I don't want to buy one if there's something we can do to fix this). Anyone else have this issue?