Rapid drop in FC after adding chemicals

#1
This morning, the FC was at 7.5. I added the following:

-40# Salt
-2# Calcium increaser
-3 qts CYA (liquid)

5:00 comes around and FC was at 5.5

Is there anything I added that combines with the chlorine to bring it down so fast?

Thanks.
 

duraleigh

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#2
The FC loss is not very fast at all......it's very close to normal.....about 2 ppm daily attributed to UV loss and organics being oxidized in your pool water.

Why did you think it was too fast?
 
#3
The FC loss is not very fast at all......it's very close to normal.....about 2 ppm daily attributed to UV loss and organics being oxidized in your pool water.

Why did you think it was too fast?
Mainly because the chlorine loss thus far from a SLAM recovery has barely been 0.5 loss/day. Then all of a sudden it dropped 2 ppm today with the addition of chemicals.

The water temp is 68* and low UV as the pool is in a screened canopy and the sunlight gets filtered through dense trees (preserve on all sides of the yard).
 

duraleigh

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#4
Given that new information, I can see your concern but I still do not believe there is a problem. I would test the water daily for maybe 3-5 days and see if your FC consumption doesn't level out.

To answer your question, there is nothing in those 3 chemicals that contributes to chlorine loss.
 
#6
Update:. I had to go out of town for a few days, so being afraid of losing too much chlorine, I added two cups of 10.5% bleach which should have brought the chlorine up 2 ppm to 7.5. Well, at last check, I was at 10 ppm with SWG off.

Something must've interfered with the chlorine testing initially after adding the chemicals even after several hours of waiting.