I have a rather old Pentair Nautilus Triton FNS 36 filter with a strange problem. Upon startup and after a few seconds of running a significant amount of de and crud discharges into the pool. After about 20 seconds it clears up and seems to proceed to filter, of course the water never completely clears up and remains cloudy. After turning off the pump the migration of de into the discharge system seems to be immediate. After being off for just a few minutes and turning it on results in de discharging into the pool, although not as much as if it's sitting overnight. There is no air in the system and no leaks. Because some of the filter grids had broken plastic framework I replaced the whole set (some of them were original). I have replaced most of the o rings and gaskets. I checked the manifold and didn't see cracks anywhere. The standpipe looks good. I can't readily see a problem with the backflow valve assembly (replaced o rings and gaskets in the backflow valve). You would think that this amount of de getting into the pool would be the result of an obvious break somewhere in the system, but I don't see it. I am out of ideas. I may have to call in a professional but trying to decide whether to put more money into this or chuck the whole thing and replace the filter assembly. Any ideas that I may have missed?