I inherited a 27ft above ground pool when we moved here (Northeast OH) a couple years ago, roughly 17.5k gallons. This has a single cartridge filter system with a Jacuzzi 1HP, two speed pump. I have to confess I don't run the pump much (a few hours once a week maybe).
Last year I came across TFP, and have been following the BBB method ever since with good success. The pool sits in a shady area with trees on three sides. Normally, the only problem I have is complaints about water temperature (I'm pretty happy if I can keep it above 80F the last couple years even with the solar cover we keep on it all the time). The pool hasn't gotten a lot of use due to the cool weather we had this summer.
This summer, I've developed what appears to be a pollen problem. There is a yellow/brown powdery substance that collects on the bottom of the pool (only bottom, not sides). I'm nearly certain this isn't algae as I never let the FC fall below about 3ppm (Taylor FAS-DPD kit), CYA ~30. Water is crystal clear, except for the pool bottom. There is virtually no chlorine load - I lose none overnight and only a little during the day even if the pool is uncovered (remember, this is a fairly shady area and is in shade from early afternoon on). I vacuum it up, and a couple days later it is back. If I run the pump overnight, next morning it is in clumps on the pool bottom.
In desperation, I treated for mustard algae - I raised FC to 18ppm, vacuumed and a couple days later the pollen was back with the chlorine still at 16ppm. I can't believe this could possibly be algae at those chlorine levels (CYA 30ppm), so I'm convinced it must be pollen.
For whatever reason, my cartridge filter doesn't appear to be catching this when I vacuum - I can see it coming back out the return. It does catch some, if I open up the filter when I'm done, the water is yellow. But there is a lot that comes right back into the pool. I've tried putting on skimmer socks when vacuuming, but that doesn't help at all. They catch bigger things, but the pollen goes right through - maybe too high pressure?
I've about reached the breaking point - tonight there was so much on the bottom that when vacuuming it clouded up the pool with everything streaming back out the return. I don't know if there is a problem with the cartridge filter, or if pollen is normally this difficult to vacuum out. Perhaps if I ran the filter on low 24/7 it would pick up more and not pull it through the filter.
Any suggestions? Would flocullant or clarifier work to make these particles big enough to catch them in the filter or skimmer sock?