FC not dropping for days. Should I be Worried?

Joe Garcia

Active member
Apr 9, 2020
29
Ft. Myers, FL
In SW Florida this time of year, it rains everyday for about 30 minutes in mid-afternoon. I normally have to put in 32 oz of bleach every other day to keep my chlorine in the 6-7 FC range. I haven't added a drop of bleach in four days. Over the last many days my FC has stayed at 7 although its continued to rain. The ambient temp is in the 91-93 degree range. Here are my current pool numbers:

FC-7
Ph- 7.4
TA-80
CH-375
CYA-35
CSI- .29
Water Temp- 85

The pool looks crystal clear and I certainly don't have any algae. My CYA is a little low for my liking, but it's not dangerously low. Is this much ado about nothing or do I have trouble brewing?
 

bmoreswim

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Jul 16, 2012
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Central MD
Per your logs, one day (4days ago to 3 days ago) your FC went up from 6 to 7 with no added chlorine. So there seems to be some testing inconsistency. Previous day our FC was 6.7 (odd reading - are you using the 10 ml water sample)? Then you added 32 oz of 10% bleach, which added roughly 3 PPM so that puts you at 9.7, then the next day (later timeframe) it was 6. So it lost about 4 in 30 hours. Normal enough. Then no loss for 3 days. Hmmm.

Testing inconsistency, old reagents, someone else adding chemicals, you have a SWG and don’t know it (joke). FC doesn’t go up by itself as it did one day. FC gets used by sunlight and organics. The three reasons above are my thoughts. FC should not stay the same in that environment.

From your original post it sounded like you had a regular routine of 32 oz to maintain an even FC level. But your logs show that you’ve have greatly fluctuating FC levels from 4.5 to about 25. One day FC went up 1.5 with no FC added. Is there something else that has been going on over the last two months?
 

Holydoc

Gold Supporter
Jul 17, 2016
418
Navarre/FL
Impossible to keep a consistent FC in Florida this time of year without adding Chlorine somehow. Something has to be wrong with your test reagents or testing.
 

Joe Garcia

Active member
Apr 9, 2020
29
Ft. Myers, FL
I think you misread, as my post said I keep FC at a 6 to 7. Either way, my reporting might not be consistent but the testing is. The only change in my reagents is a new bottle of R-0871. Nothing else has changed. My FC has dropped .5 in the last 12 hours which included overnight. The fluctuation in the logs of up to FC 25 was because I had to SLAM sometime back. The pool has been great since then. I still haven't added any chlorine. I just don't get it.
 

bmoreswim

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Jul 16, 2012
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I think you misread, as my post said I keep FC at a 6 to 7. Either way, my reporting might not be consistent but the testing is. The only change in my reagents is a new bottle of R-0871. Nothing else has changed. My FC has dropped .5 in the last 12 hours which included overnight. The fluctuation in the logs of up to FC 25 was because I had to SLAM sometime back. The pool has been great since then. I still haven't added any chlorine. I just don't get it.
I understood the range you keep it in. Your logs show it increasing from 6 to 7 with no chlorine added. That is testing error in all likelihood. I saw another similar anomaly in data as well back a few weeks.

As with all good things, they don't last forever. It will come down or your water will turn green. One of the two. If you are comfortable with your FC and CYA testing, then just wait until the pool tells you it needs more.