No chlorine in pool this morning, can’t figure out why?

Aug 28, 2016
Baltimore Md
I have noticed my FC levels have been low this year and came out to zero chlorine about 10 days ago, I assumed it was the filters because I had seen the De not sticking so great to filters so I put in new and cleaned the IC40 chlorinater re tested the next day and the levels were better FC was at 2 and checked every day they stayed around 2 which for having my IC40 set at 50% those numbers still seemed low. Again this morning I came out to no chlorine in pool and that’s after bumping IC40 to 60% yesterday, all lights are happy on the IC40 and salt levels are 3400 ish. I am thinking about replacing the IC40, not sure what else to do.

FC 0
Alk 110
Ph 7.3
CA 300
Cya 90
Last edited:


Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

I doubt your IC40 is bad, it is a little small for your pool, but I suspect that you have algae, even if you can't see it yet.

You need to run an Overnight Chlorine Loss Test or OCLT... Overnight Chlorine Loss Test

Your main problem is running your FC at 2 ppm... An FC of 2 is below the minimum in most cases..

Tell us what your CYA level is... You should always try to maintain your "Target" FC per the saltwater section of this chart. FC/CYA Levels


Jim R.
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Well-known member
Jun 19, 2020
At CYA 80, FC should never be below 4. Since you've been below minimum, and especially because you've been below minimum for and extended period of time, you almost certainly have algae.

You'll need to get several gallons of liquid chlorine, adjust pH to 7.2, and begin a SLAM. You can raise the FC level using liquid and do an OCLT tonight to confirm, but you have several indications that it's algae.
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