OK - I have been reading this forum for about 3 years now and have learned a lot, but apparently I still have much more to learn. I started using the BBB method 2 years ago with great results, and I have had crystal clear water after usually only a couple of days, using a modified SLAM method (just threw in about 5 gallons of Sodium Hypochlorite 12.5% after opening and voila - about 3 days and a few dozen vacuuming sessions and worm retrieval sessions later the pool was clear; then I would correct the other chemistry as needed).
We have had this pool, an 18'x36' 22,468 gallon pool for about 12 years now, and one way or another things would work out. But after reading here I now realize I used way too much chlorine (so far no noticeable ill effects), but I know my ph was off and I have lots of small wrinkles on the bottom of the deep end and a few small ones in the shallow end. Those will have to wait until I replace the liner, which I estimate to be in about 2-3 years, just to be safe.
Anyway, back to this years problem. I live in upstate NY, and we have had a safety winter cover for about 3 years. This resulted in a much greener pool than we were used to when we opened it, and also much dirtier (sand and grit) because of the porous nature of this type of cover. But it is easy to take off and looks nice and keeps the grandkids safe when they visit, so I live with it. This year we had a few very warm days in late April/early May, and I didn't get the cover off until last Wednesday. It was very green.
So I poured in my first 4 gallons of "chlorine" (my name for the NaClO 12.5%) left over from last fall. And the pool went from green to cloudy turquoise - so cloudy I could not see the bottom of the deep end. I put DE in the filter and started vacuuming using the hose that goes into the skimmer and through the pool circulation flow. After 2 more days and about 5 more gallons of fresh "chlorine" the pool was still very cloudy but was slightly better. So at this point I did another backflush/DE recharge cycle and started vacuuming with the robotic vacuum (Hayward AquaVac). This uses internal reusable filters to clean the pool. The first day I forgot to put in the donut over the main drain, partly because I couldn't see it (really just because I forgot and not seeing the bottom didn't remind me of it), but after noticing the robot getting stuck in that vicinity I would move it by hand. After the first two sessions, I could almost see the drain and attempted to drop the donut over the drain, and apparently by some stroke of luck I actually succeeded (couldn't actually tell until a few days later when I could actually barely make out the drain/donut, but it wasn't getting stuck so I figured I was close enough).
So two days ago I re-read about SLAM, took my pool readings (FC - 0, CYA - 0, ph - 8.0 - didn't check the others). So, after checking the Pool Calculator, I then added about 4 more gallons of "chlorine", about a quart of Muriatic Acid, and about 2 pounds of CYA. FC/TC quickly went up to 10+. In the meantime I have been running the robot for 2 hour sessions 2-3 times daily. Also, the pump is on 24/7. The chlorine pump is not adding any "chlorine" automatically, only what I add manually.
The current pool temperature is about 66-68 degrees F.
I checked the FC/TC yesterday morning and it was still about 10 - I didn't check anything else.
This afternoon I checked and the FC was 3.0, TC was 3.5, TA was about 40, CYA was still about 0, and pH was down to a nice 7.2. Still vacuuming. The water is just slightly clearer (I can make out the donut over the drain and follow the robot in the deep end), but this seems to be taking too long.
The robot filters seem to be very full of a light gray fine material, and have been extremely full (about 1.5 pounds of the stuff each session - maybe 8-10 sessions) except for the very last one I pulled out at dinner time, which was finally only about half full.
There still seems to be a little of the stuff near the seams of the liner - but it looks a little better each time. But the water is still very cloudy.
So - two questions. I have never opened the filter (Pentair FNSP 36 DE filter) in the 12 years I have owned the pool (some say open and check it each year, others say if it ain't broke don't fix it), and I haven't had any problems so far. Could DE be leaching into the pool? I haven't put in as much DE (about 6 pounds so far) as I have removed in gray material, but the stuff feels/looks like DE. Is there any way to check this without opening and inspecting the filter? What are the downsides to opening up the filter?
What should I do next?
I am posting a couple pictures (the deep end, where you can barely see the donut, and the vacuum filters - one clean, one dirty).
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