Thanks for taking my question. The pool is 17k gallons, plaster, in FL with a cage around it. The owner re plastered last year with no problems. Hayward cartridge filter using Unicel filter (only 1 month old C-8409 model number).
Readings as of last night at 6pm:
CH 300 (FL has hard water)
No metals - on city water
I'm filtering 24/7 and spraying the filter out every 12 hours.
I use the Taylor k-2006 kit and have compared my tests to the pool store in the past. Reagents are from this year. Brand new bottle of R-0871. Yes, there is a pool store that actually does the tests correctly. Each time our test results are nearly identical.
The issue is ongoing green algae. The water keeps getting a green tint to it. When I sweep it clouds up into a little green cloud. Last night I used 2.5 gallons of liquid chlorine. This morning at 9am I sprayed the filter out. The FC was very high, at least 15ppm. I stopped counting the drops after I hit this number. The r-0871 bottles are a bit expensive. The water sample was still bright red/pink color which leads me to believe the FC was at 20ppm, or possibly higher. The FC held very well. It didn't bottom out at all.
This has me very confused. I understand shock is maintaining a FC of 10 - 12ppm to kill the algae. I use no floccs, clarifiers, phosphate removers, etc.
I thought having the FC up that high would definitely kill the algae but it doesn't. The water did clear up a bit but when I swept this morning there still was a slight green on the edge of the steps. I swept the floor and it was like I never swept or vacuumed the day before. Algae just came right back.
A couple weeks ago the CYA was low and I used about 2 lbs. of trichlor. The CYA was about 20ppm on the K-2006 kit. The CYA was about 40ppm after the trichlor and the water looked perfect with all of the other readings in order. I maintain the FC of 2 - 4ppm. When the FC got to 3.8ppm this time is when the green started back. We get lots of rain in FL right now and with the splashing out and topping off the CYA never really gets about 50ppm.
Please help as I'm stumped on what to do next.