Losing chlorine quickly

[Dt103]

I cant keep chlorine in my pool. Ive tested with a Taylor K2006C and below are my numbers

FC 0
CC 0
PH 7.4
TA 100
CH 340
CYA 78
Salt 3900
I live in Florida and my pool is in direct sun. I have a new SWG made for 60k gallons but my pool is 20k gallons. I increased my CYA this morning from 47 to 78 and since then my Chlorine has dropped to zero. I took a sample from the jet and my cell is producing chlorine. So i dropped a bag of cal hypo shock to boost chlorine at noon and two hours later im back to zero. The water looks great right now but I can’t figure why my chlorine is disappearing.

 

[mknauss]

Welcome to the forum!
Do an Overnight Chlorine Loss Test tonight.
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

 

[Dt103]

Welcome to the forum!
Do an Overnight Chlorine Loss Test tonight.
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

I’ll give it a shot tonight. Thanks.

 

[Dt103]

Welcome to the forum!
Do an Overnight Chlorine Loss Test tonight.
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

So it didn’t take long to see that I was losing chlorine after the sun set, so I started my SLAM last night. I expected this after you said to do the test so I went and picked up plenty of liquid chlorine. I replenished to slam level at 5am this morning and just replenished at 3. I only needed a small amount to get back to slam this afternoon so I’m hoping all will be well by morning.