Free Chlorine Level Went to Zero

[jliddil]

I use the TFT100 Kit
CYA=70
pH 7.2
TA 80
Ca=400
Cl=0

I thought I had a dirty SWG cell as my Cl was 2 ppm 5 days ago. I cleaned it and the chlorine was down to zero today. The water is a bit opalescent. I add DPD to 10 ml of water and got no color.
Went to the pool store to test the cell. It passed. So they tested the water for TC I assume using DPD and they waited a few minutes and the water turned pink.

The manager gave me a few bags of persulfate as he said the chlorine was likely bound up as chloramines. I have added the persulfate and cranked the SWG up to 80. (it a Hayward unit). Now I have more than 5 ppm. Have not done a drop test.

I have never had this issue before. I am in the Tampa florida area and my pool is screened in. I'm really the only one who swims in it. I'm going to do an overnight test to confirm the chlorine stays up. I've also been brushing it on and off today as well as skimming.

Thoughts?

 

[jblizzle]

I think you need to be a little more proactive.
With a FC of 2ppm, you should have added some FC ASAP with bleach. And you should not be waiting 5 days between testing.

We would not have recommended the persulfate and that is going to skew your test results.

At this point, you need to follow the SLAM Process process to eliminate whatever is in your water consuming the FC. And then dial the SWG back in.

 

[jliddil]

Well by the afternoon the free chlorine was 6 PPM. This morning the FC was at 5 and the CC was 0.5. As of right now the readings are the same and the water is clear.

 

[Texas Splash]

Interesting turn of events. Curious, when you compared yesterday and this mornings FC, was the SWG off? Just want to ensure you had an accurate OCLT.