What the heck is going on!? FC levels not adding up... So confused..

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T

tbird2340

Well-known member
Jun 3, 2014
224
Youngstown, OH
Some background.. Second year pool owner.. Been doing TFPC method since I got it.. Never had anything but crystal clear water..

This year I definitely didn't test as much as last year but still had no issues.. Got ready to close my pool.. Here's what I did..

Checked FC and it was at 3.. PoolMath said to add 187oz of 8.25% to bring it to 12 so I did that.. Left the pull uncovered for the first time over night.. Let the pump run on high the entire time.. Checked FC about 24 hours later and it was 7!! What the heck??

So I go to PoolMatch again and enter 7 to get to 12.. It says 107oz.. I put in an entire jug of 8.25%.. Same deal.. Leave it uncovered, pump running on high for 24 hours.. Checked it just now.. FC IS SEVEN!!!! Is there some flesh eating bacteria that I'm not seeing or what is going on here??

9/21 - 5:30pm
FC - 7
PH - 7.6
TA - 110
CA - Guessing around 20ish?? I filled it to the top (30) and still saw the dot a little..

This summer I was putting in about 80oz of 8.25% every few days..

Please help a brother out..

Thanks!!
 
Let's try to help you. :) The one thing that stands out right now is your CYA (you listed as CA) being 20-ish. That means it actually could be lower if the black dot never went away. If that's true, then you may very well have next to no stabilizer in the water. That would mean your FC is getting consumed by the sun very, very fast. You should verify that CYA reading, and if it is indeed next to nothing, target for a CYA of 30. I know you're getting ready to close, but the only other thing it could be is algae. To check for that you would have to do an OCLT to confirm. I see those as your two best options to check.
 
Does your K-2006 test kit have the CYA mixing bottle and the skinny tube with the black dot at the bottom?

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If so, that skinny tube should have measuring lines that go from 100 to 20 ppm.

Proper lighting is important for the CYA test. You want to test for CYA outside on a sunny day, but keep the skinny view tube in the shade. Taylor recommends standing in the sun with your back to the sun and the view tube in the shade of your body. Use the mixing bottle to combine/mix the required amounts of pool water and R-0013 reagent, let sit for 30 seconds, then mix again. Then, while holding the skinny tube with the black dot at waist level, begin squirting the mixed solution into the skinny tube. Watch the black dot until it completely disappears. Once it disappears, record the CYA reading. After the first test, you can pour the mixed solution from the skinny view tube back to the mixing bottle, shake, and do the same test a second, third, or fourth time to instill consistency in your technique, become more comfortable with the testing, and validate the CYA reading.
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Checked FC and it was at 3.. PoolMath said to add 187oz of 8.25% to bring it to 12 so I did that.. Left the pull uncovered for the first time over night.. Let the pump run on high the entire time.. Checked FC about 24 hours later and it was 7!! What the heck??

So I go to PoolMatch again and enter 7 to get to 12.. It says 107oz.. I put in an entire jug of 8.25%.. Same deal.. Leave it uncovered, pump running on high for 24 hours.. Checked it just now.. FC IS SEVEN!!!! Is there some flesh eating bacteria that I'm not seeing or what is going on here??
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Here is my recommendation:

Test FC at night or day (with no sunlight for most part). Then add 107 oz. of 8.25% and wait exactly 30 minutes, no more than 1 hour and test again. Register the reading and then wait 24 hours and test again. If you are loosing that much, then you might be ready for a SLAM. Your CYA as mentioned also would need to be verified and adjusted accordingly. Based on your testing, the 24 hour loss is 5 ppm. Hopefully it is the strength of the bleach and nothing else lurking in your pool. You will know if you test before the addition and shortly after.

The reason why I mention this is that you want to be 100% certain that the 8.25% raised your FC reading by 9, and nothing less. Anything less means you are not really loosing as much, and one would want the most accurate data as possible to determine any issues. The bottles always say 7.86% available (something to this affect), so I always use this figure. I work with 12.5% and use Chem-Geek's degradation schedule, which is based on storage temperatures and time. Everything is adjusted monthly based on the schedule.
 
Ahhh I see now. The fact that you still see the dot on the left side of that comparator is a problem. You definitely want it to fully disappear at 30. As long as the black dot is still there, your CYA is below the minimum recommended level of 30 to adequately protect your chlorine. Consider adding enough granular stabilizer to increase by at least 10 ppm, that way you don't go too high. Then you can adequately prepare for closing. Remember though, it takes about a week for stabilizer to start showing on your tests.

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In the meantime, while you wait for the stabilizer to increase your CYA, you could also do an OCLT to rule-out algae.
When performing the OLCT, remember that it must be done when the sun has dropped – no sunlight on the pool. About 8 hours total is recommended. Also, your FC level should be elevated more than normal. Starting (bedtime) FC could be close to your SLAM level, but no lower than 10. Anything less and you may not receive an accurate portrayal of FC loss (by percentage), even if it’s only 1 ppm.
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Catanzaro said:
Here is my recommendation:

Test FC at night or day (with no sunlight for most part). Then add 107 oz. of 8.25% and wait exactly 30 minutes, no more than 1 hour and test again. Register the reading and then wait 24 hours and test again. If you are loosing that much, then you might be ready for a SLAM. Your CYA as mentioned also would need to be verified and adjusted accordingly. Based on your testing, the 24 hour loss is 5 ppm. Hopefully it is the strength of the bleach and nothing else lurking in your pool. You will know if you test before the addition and shortly after.

The reason why I mention this is that you want to be 100% certain that the 8.25% raised your FC reading by 9, and nothing less. Anything less means you are not really loosing as much, and one would want the most accurate data as possible to determine any issues. The bottles always say 7.86% available (something to this affect), so I always use this figure. I work with 12.5% and use Chem-Geek's degradation schedule, which is based on storage temperatures and time. Everything is adjusted monthly based on the schedule.
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OK. I just tested after adding 121oz of 8.25% Clorox and waiting 30 minutes and it's 11.5 FC..

So now wait 24 hours and test again? What should it realistically be?
 
OK. I just tested after adding 121oz of 8.25% Clorox and waiting 30 minutes and it's 11.5 FC.. So now wait 24 hours and test again? What should it realistically be?
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Did you test before the addition? if so, what is the reading? This way, you can determine is the increase, based on your pool size is accurate. We can only start with fresh data. Try testing a second time at the 1 hour mark. If you have time, then possibly test early in the a.m., and then at the same time next day (24 hours later).

Each pool is different, so it is hard to answer this one. If you loose more than 3 ppm, with no activity, I consider that excessive. It appears that Ohio is a bit on the warmer side, although this should not make that much of a difference.

Please post results (if possible) as follows: Hopefully, I am correct on the times, or at least close.

Test after 30 minutes (8:00 p.m.) is 11.5 FC
Test after 1 hour (8:30 p.m.) is
Test at 7 a.m. is
Test at 8 p.m. is

I ask you this, because we can confirm that after 1 hour, the bleach has been mixed thoroughly and the readings are accurate. The overnight test, although 11 hours apart is still fine at this point because of no sun (for the most part), and then 24 hours later to determine how much you lost in a full day. This will conclude the testing, and probably be start of the SLAM process.

As Texas Splash mentions, probability is that your CYA is low and will need to be increased to the recommended levels to ensure you are not loosing a lot of FC due to sun exposure because of low CYA.
 
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Tbird, you received different guidance from two parties - myself and Catanzaro. My recommendations are listed above. Your FC loss is from one of two things: the sun (with little to no CYA available) or algae. A way forward is provided for you to pursue checking for either or both of those items. If you have any questions about my inputs, please let me know. Have a good evening.
 

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Yep. And like I noted above, without making the whole thing too complicated right now:
When performing the OLCT, remember that it must be done when the sun has dropped – no sunlight on the pool. About 8 hours total is recommended. Also, your FC level should be elevated more than normal. Starting (bedtime) FC could be close to your SLAM level, but no lower than 10. Anything less and you may not receive an accurate portrayal of FC loss (by percentage), even if it’s only 1 ppm.
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You still need to confirm that CYA though. With little to no CYA available, little to no FC will remain in the water during the day.
 
tbird2340 said:
Again though.. How do I verify it when the lowest reading it can give is 30? Do I assume it's around 20 and add enough to bring it to 40?
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I don't usually recommend using liquid stabilizer, but in the interests of time (you are closing soon), I would go get some liquid stabilizer and add enough to increase your FC by 20ppm (the test has a practical error of +/- 15ppm). Then test 24 hours after you add it to see where you are at.
 
Exactly. To be safe (so you don't go too high), you could add only enough stabilizer to increase by 10 ppm, that way if it is 20 now, you'll get to 30. Going to 40 is not the worse thing either, so if you add 20 ppm it's okay. But later if you do need to "SLAM", you 'll use a little more bleach, that's all. But you definitely need for that dot to disappear so you can confirm your CYA.

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Matt has a good point about the liquid if you don't mind spending a few extra $$ on the liquid form. Time is of the essence for you right now.
 
I think you're right. You seem to be holding FC well with no sun. That's good. That conditioner should work fine. You'll probably notice the active ingredient of "Cyanuric Acid" on the container. Use the Poolmath calculator to shoot for that target of 40 ppm of CYA as recommended and try to keep the FC level at 5 as noted on the Pool School - Chlorine / CYA Chart. Watch the FC closely for the next 24 hours or so as the pool adjusts to the conditioner/stabilizer. Perhaps confirm CYA tomorrow. Good luck!
 
TBird:

Great Job. Please stay with the same sample size (10 ml.) so there is no confusion. Based on your results, you a 1.5 ppm FC drop in an 11 hour loss (not bad). Please get that conditioner in the pool as Texas Splash recommended. No more additions until you test this evening to determine how much FC you have lost. Please keep us posted.

The liquid conditioner from Leslie's, including tax will be close to $40. Amazon is a lot less expensive, although it will take time to get to you.
 
It takes about 24 hours for the liquid to fully mix with the water and show on the CYA test. For now, go ahead an begin to increase your FC level on that new (projected) CYA. I believe you set a new CYA target for 40 correct? If so, then add bleach with a projected FC target of 5 ppm. The Poolmath calculator can help if you need it. Stay with that routine through tomorrow and check back in with us. By then, your CYA should have increased which should in-turn help to protect the FC better. Don't let the FC drop below 3 though.
 

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