I have a 15,000 gallon pebbletec playpool that gets FULL sun from nearly sunrise to sunset (no trees, no shade from anything).
Here in AZ, we had a huge dust storm almost a month ago that left the pool quite a mess. I thought it was all cleaned up, but I saw some brownish "stains" on the bottom. One was approx. 18" circle, one 12" circle, several other smaller circles. Silver dollar sized spots on the large swim step. When I brushed, I could see moderate algae but the "stains" did NOT come off at all.
I didn't take a photo of the algae, but it was HIGHLY aggressive. I would brush and within an hour I would need to brush again. The stuff that did brush off was on the shaded walls and looked just like mustard (although I don't know enough to determine if it is actually mustard algae - and I tried looking at lots of photos).
My shock process started Saturday evening when I added 9 gallons of 10% liquid chlorine (should have created approx. 54 ppm - but the chlorine was 2 months old and despite the 74 degree storage temp, only generated approx. 27ppm). Super filtered, yeah right....had a bunch of solids on the bottom of the inside of the jugs.
My CYA is approx. 85 and I do have the TF-100 kit.
Here are my actual chlorine results.....
7/30 (Sat sunset initial test) 1 ppm Add 9 gal 10% older chlorine
7/30 (Sat at sunset) 27ppm
7/31 (Sun AM) 20.5 Add 5 gal older 10% (approx. half strength)
7/31 (Sun PM) 32 ppm
8/1 (Mon AM) 28 ppm
8/1 (Mon PM) 23.5 ppm Add 2 gal 10% NEW stronger chlorine
8/1 (Mon Late PM retest before bed - 1 hr after adding chlorine) 32ppm
8/2 (Tue Early AM - before sunrise) 30ppm (only lost 2 ppm overnight in 7 hrs) Add 3 gal 10% older chlorine (yes, had a lot left over)
8/2 (Tue Late before bed) 22 ppm
I have been brushing the pool 3-4 times per day and now the water looks milky when brushing (I think that is dead algae). However, I can brush 30 minutes later and it appears to be just as much algae on the bottom, like it keeps returning.
I couldn't find my vac, so I threw in the Polaris (didn't want to with 22ppm chlorine and had it out for shocking). Backwashed 3 times tonight (sand filter), each time looking white for 20-40 seconds.
I don't want to throw in more chlorine and trash the Polaris, but I'm not sure if i'm done fighting the algae (I don't want to do this again!).
Without the Polaris, I don't see the white cloud of algae on the bottom ever leaving.
Pool looks really good, until you brush it!
Filter runs 17 hours a day on high (off from noon to 7pm during peak power pricing). Water temp approx. 92 degrees - HOT!
Read the whole pool school and it says this might continue 2 weeks and that when ppm drops only 1 overnight you are good. Mine was 2 last night, but my residual chlorine is still 22, so I'm guessing it will fight tonight still.
Should I do anything special, or just keep brushing and let the chlorine fall back to 5ppm?
SWG is being installed in the next week or two....I can't handle doing this again!