Post-Slam/OCLT: FC Loss

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T

Tanker

0
Sep 20, 2014
23
Elgin, IL
Hi. I had to close my pool early last fall and it was a bit green when I opened. I did a slam and passed an OCLT for two nights in a row, the second OCLT passed this morning. The water is sparkling. I decided to let my FC drift down. Here are my current numbers:

FC 14
CC. 0
PH ? Was 7.2 before slam
TA 130 (will work on this later)
CH 170 (need to raise for my heater later)
CYA just under 40

This morning the FC was 18 with 0 loss overnight. I lost 4ppm during the day today. I plan on testing FC/CC again after dark.

I am wondering if FC can fall that fast or if I have an issue. Any advice?
 
A loss of 4 sounds reasonable with under 40 CYA.

The higher the FC, the faster it drops. It's not a fixed parts per million, but a percentage. So the higher the starting point, the more you lose. Part of the reason we don't push for a higher FC level during the SLAM -- so much gets lost to the sun at higher levels.

Trust your results. You ran the OCLT twice and it was fine. You've ruled out organics, so it has to be sunlight. I know somewhere there's a graph. I should go hunt for it.

Update: Second and third graphs should put your mind at ease. Pool Water Chemistry
 
I am in big trouble. Please help. First OCLT passed Saturday/Sunday. The second on Sunday/Monday.

Tuesday's results (FC was 14 after dark Monday night) CYA <40
6:30am FC was at 10 CC 0 (an hour after sunrise: Out of fresh bleach)
12:30pm FC 7.5 CC 0.5 Added to bring to 14. Walls feel a little slimy; brushed. PH 7.3
4:30pm FC 12 CC 0
5:30pm FC 11.5 Added to bring to 12.5

The only thing different is on Sunday:
1) we put the ladders in. The outsides were scrubbed with bleach water. Could there be algae spores in the metal tubing? I took the ladders out and took the caps that sit against the pool surface off and only see dirt, nothing green. Left ladders out.
2) pool floats were in the water on Sunday also

Light niche was scrubbed at opening.

I don't understand what is happening.
 
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