FC struggles

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TRUK71

TRUK71

Well-known member
Jul 21, 2020
159
Indianapolis, IN
Pool Size
7000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Jandy Truclear / Ei
Last year I had zero issues with water chemistry. This year has been a battle from the get go. In particular my FC and I'm struggling to understand why. It's having big swings. Last year I ran my swg at 30% pretty much the entire year. This year I cant find a setting that will keep it a steady figure. My cya is a 70, my pH is 7.2, cc is 0, ch 370, ta is 110. I had my swg at a 30% recently and my FC went almost to 0. So I increased it to 70% to get it back up and it jumped all the way to a 15 in 2 days. So I bumped it down to a 50% trying to bring it down slowly so I can get a good fix for what swg needs to be at. So at 50% in 2 days in dropped to a 5.4 The only thing different between this year and last year was the pool opening. Now having said that that was about 2 months ago. When my pool company closed the pool last year they stated they put 70 gallons of antifreeze in the lines (which I've been told on here is ridiculous and can't be accurate) and when they opened the pool they pumped the entire amount of antifreeze into the pool. They told me it would evaporate in a couple days. So I was told by a member on here to slam my pool to try to eat up the antifreeze, which I did for 3-4 days. So it's been 2 months and I've slammed the pool so the antifreeze has to be gone, or so I assume. So why is my FC jumping all over the place. It hasn't been used more than normal, it hasn't been overly sunny and my cya has been very consistent between 60-70. Any help would be greatly appreciated.
 
SWG is 1 year old. I cleaned it at end of last year. It's not 100% clean but it's 98% clean. I did the over night test when I slammed a month ago. I will do again this evening.
 
I thought the CC reading on test gave indication of any organic material or algae in water. Am I incorrect in that understanding?
 
In a situation like this, adding a specific amount of liquid chlorine to rapidly raise your FC to a safe target, testing after 30 minutes to verify after application and before your SWG restarts then again after a full SWG run would help diagnose your issue. This assumes you are not running your SWG on a 24 hour setting.
 
CC is a by product of chlorine oxidation of anything in the pool. It is constantly broken down and created in a pool environment, so you may not catch a sample at the time it is present in the water. CC levels of .5 are normal and nothing to be alarmed about. It is possible to have algae and not have CC in the pool when doing tests.
 
I would go ahead and raise the FC to slam level tonight and let it circulate overnight. What is your current FC target? I'm thinking it should be 5ppm. Could you ammend you signature to include pool size and whether it is plaster, vinyl, or fiberglass surfaced?
 
TRUK71 said:
Last year I had zero issues with water chemistry. This year has been a battle from the get go. In particular my FC and I'm struggling to understand why. It's having big swings. Last year I ran my swg at 30% pretty much the entire year. This year I cant find a setting that will keep it a steady figure. My cya is a 70, my pH is 7.2, cc is 0, ch 370, ta is 110. I had my swg at a 30% recently and my FC went almost to 0. So I increased it to 70% to get it back up and it jumped all the way to a 15 in 2 days. So I bumped it down to a 50% trying to bring it down slowly so I can get a good fix for what swg needs to be at. So at 50% in 2 days in dropped to a 5.4 The only thing different between this year and last year was the pool opening. Now having said that that was about 2 months ago. When my pool company closed the pool last year they stated they put 70 gallons of antifreeze in the lines (which I've been told on here is ridiculous and can't be accurate) and when they opened the pool they pumped the entire amount of antifreeze into the pool. They told me it would evaporate in a couple days. So I was told by a member on here to slam my pool to try to eat up the antifreeze, which I did for 3-4 days. So it's been 2 months and I've slammed the pool so the antifreeze has to be gone, or so I assume. So why is my FC jumping all over the place. It hasn't been used more than normal, it hasn't been overly sunny and my cya has been very consistent between 60-70. Any help would be greatly appreciated.
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Chlorine shouldn’t be jumping around unless there’s something it’s eating at. That said, it’s normal to have to adjust the SWCG output over the season. You can’t leave it set to one number and expect it to go the whole season.

Since you turned it up and the FC went up, I’d say it’s working fine. You just need to test more often to make sure it doesn’t get to 0 again (Actually not let it get below your minimum for the FC/CYA chart). If it gets to 0, you will get algae growing.
 
zea3 said:
I would go ahead and raise the FC to slam level tonight and let it circulate overnight. What is your current FC target? I'm thinking it should be 5ppm. Could you ammend you signature to include pool size and whether it is plaster, vinyl, or fiberglass surfaced?
Click to expand...
Target is a 5. Updates signature.
 

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Bperry said:
Chlorine shouldn’t be jumping around unless there’s something it’s eating at. That said, it’s normal to have to adjust the SWCG output over the season. You can’t leave it set to one number and expect it to go the whole season.

Since you turned it up and the FC went up, I’d say it’s working fine. You just need to test more often to make sure it doesn’t get to 0 again (Actually not let it get below your minimum for the FC/CYA chart). If it gets to 0, you will get algae growing.
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I test it almost everyday. At least 5 days a week.
 
Several other things can affect FC demand, such as wind born debris, swimmer load, sunscreen use, and excessive rains. Experimenting with percentages and run times like you have been is still the best way to find a good setting but it may not give an exact, steady FC level. As long as you can keep the pool between 4-7ppm you shouldn't develop any problems. I choose 4-7 just to give you a little extra wiggle room. Its not uncommon for FC to drop by 2ppm after a swim, and targeting 7ppm insures you won't drop below 3ppm.
 
Bperry said:
It went from 15 to 5.4 in one day? Seems almost impossible unless you have ammonia in there.
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It was over 2 days. Ammonia would eat up all the chlorine in minutes and he would have 0 CYA. I think the excess antifreeze created an increased FC demand, and since we can't test antifreeze levels the best we can do us use slam criteria to determine if it is gone.
 
zea3 said:
It was over 2 days. Ammonia would eat up all the chlorine in minutes and he would have 0 CYA. I think the excess antifreeze created an increased FC demand, and since we can't test antifreeze levels the best we can do us use slam criteria to determine if it is gone.
Click to expand...
But it also went from 0 to 15 in two days as well with only a 20% increase in power output. That’s a huge spike both ways. Will antifreeze do that?
 
The pool service company claims to have used 70 gallons, maybe they did, maybe its a typo. We have no way of knowing for sure. Even if it was just 7 gallons, that is still a lot of antifreeze to dump into a 7000 gallon pool.
 
I had a similar thread a bit back but for a bit of a different issues. Joyfulnoise had me slam and I did and thought I was good.
 

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