This problem started out of the blue. I noticed what appeared to be pollen on the pool floor and went to vacuum it out. I noticed that out of the returns that there was actual debris as in leaf stems and parts of black leaf materiel blowing into the pool (stuff I was vacuuming out).
Prior to this our pool was sparkling clean (for over 4 years). I have taken the grid assy. out twice looking for a tear in the grid. First time just pulled the grid, hosed it off and did a minor inspection and put it back together. Still DE was entering the pool. The second time was a complete disassembly of the grids and had three people looking closely for any kind of tear and abrasion, nothing found.
I did notice that two of the grids had a layer of crushed supports inside the fabric (very minor and almost not noticeable) but no tears.
Put it back together and there was no difference with the problem. When the pool starts I can see small pieces of black debris coming out of the returns.
I can vacuum it clean in the morning and by evening can see the first signs of DE powder in "drifts" along the steps and bottom. Also when the pump first starts I can see small black objects coming out of the returns.
This is what I have for filter and multiport,
http://www.poolplaza.com/C-Pentair-Top- ... -4279.html
Is it possible that the problem may be the multiport? I have made some stupid mistakes (in the beginning) like closing the multiport and accidentally turning on the pump and doing backwash and rinse without turning off the pump.
One thing that I did notice was that the exhaust fabric ring (opening) on the grids was not a super snug fit and was thinking about some hot glue to seal them tightly. even with that It did not seem large enough to pass the black looking debris and the fact that it seemed to happen overnight tells me that something just gave out.
Any ideas or speculation welcome.
Thanks for this great forum, as a new(er) pool owner have learned a lot and have not needed to post because most of my questions are answered here.