CC Level?

Yellowbug33

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Jun 2, 2010
42
My CC level (Taylor Test Kit) has usually been <0.1/0.2 level most of the season since spring. The past few days it has risen 0.3, and up to 0.6 so I gave it some liquid chlorine to the breakpoint dosage which for 0.6 was 6 but the FC was 10 late night when i tested so I was beyond the 6 ppm. My CC measured 0 the next morning. This morning I tested and the CC is now 0.3 while my FC is 4.6ppm
No one has been in the pool since i put the chlorine in as all day yesterday it was too high.
I thought the CC should be 0.2 or less. Am I wrong and worrying about nothing? I was surprised my FC dropped so quickly as it was holding pretty good the week we had temps in the 90's.
 

duraleigh

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Essentially, anything .5 or less is not worth worrying about.

How are you measuring in .1 increments?
 

Yellowbug33

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Jun 2, 2010
42
I measure with the Taylor--2006. If color change is close and one more drop seems over I write down the inbetween Number for my measurement. Where have you see .5 For cc is ok. Everything I've ever read has always said to try to keep between 0.0 and 0.2? I see the Taylor Testing guide shows 0.0.2 for residential inground pools and 0.5 is the max they show for public spas.
 

dmanb2b

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Apr 4, 2009
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Yellowbug33 said:
I measure with the Taylor--2006. If color change is close and one more drop seems over I write down the inbetween Number for my measurement. Where have you see .5 For cc is ok. Everything I've ever read has always said to try to keep between 0.0 and 0.2? I see the Taylor Testing guide shows 0.0.2 for residential inground pools and 0.5 is the max they show for public spas.
Have you read Pool School? Most of us here use 0.5ppm CC or less as a guideline. Testing at 0.1 or 0.2 increments, you are being too precise. I understand the k2006 instructions call for a 25ml sample to perform the Fas-dpd FC/CC test, but if you use a 10ml sample you can measure in 0.5 increments and is more than sufficient and in the process you'll use a lot less reagent.

Have you performed an overnight FC loss test?
 

Yellowbug33

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Jun 2, 2010
42
Here is my overnight test results and I have been told I am precise :eek:)
Thanks! My Hardness was low and naturally the pool store told me to put in 14LBS. They sold it in 25 pound buckets. I asked if they had something smaller and he said oh, you'll be using it. So i got the food scale out and measured 12 lbs. That is why the hardness has been up since shortly after opening. Same for cya as I couldn't get it up after a week so i added a tad more. But I think all readings are basically within range. My TA went up after 3 1/2 inches of rain in 2-3 days.

9:50pm
FC 3.6
CC 0.4

6am following morning:
FC 2.0
CC 0.4
ph 7.4
TA 120
Cal Hardness 330
CYA 55
 

benavidescj

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Apr 27, 2010
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Fleming Island, FL
Your FC is dropping to a very low 2 ppm. You should be maintaining a ppm level of 5 to 7 ppm for your CYA level. Could be that you are borderline and you are seeing some organics when your FC level drops low.
 

bk406

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Dec 3, 2009
2,690
Central Massachusetts
Yellowbug33 said:
My Hardness was low and naturally the pool store told me to put in 14LBS. They sold it in 25 pound buckets. I asked if they had something smaller and he said oh, you'll be using it.
Just an FYI. Your calcium hardness is/was fine. You have a vinyl liner pool and it doesnt need calcium like a gunite pool does. Only reason you need any calcium at all is to potentially keep a level where your heater warrenty is still good. Also, I like a little in the pool since to me very soft water doesnt feel as right as water that is a little harder. But 330 ppm is very high for a vinyl pool. It wont hurt anything, but could be a scaling issue if it gets much higher and the pH goes up. Dont add any more calcium. For comaprison, I keep mine around 70-100 ppm.
 

Yellowbug33

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Jun 2, 2010
42
So benavidescj are you saying my FC level should constantly remain at 5-7ppm or are you saying to shock it and keep it at that per the shock directions? I'm a tad confused as i thought the highest to swim at is 4ppm so I assume to get it to hold chlorine???
 

duraleigh

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Yellowbug,

With a CYA level of 55ppm, your FC should ALWAYS be at 5-7ppm. Refer to the FC/CYA relationship chart in pool school.
 

Yellowbug33

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Jun 2, 2010
42
I referred to the FC/CYA relationship chart in pool school. It states the following: The shock levels shown have equivalent effective disinfecting chlorine amounts. At high CYA levels it may be impractical to use such high FC levels, lower FC levels are often sufficient though they take longer to kill algae.
That is why I asked about shock as the statement there states the shock levels. I was an average chemistry student years ago but is there something that makes the FC level of 5-7 safe to swim in because i have a higher CYA level. As I have mentioned before I always thought 4 was the highest to swim in or am I just dense in my "older age"?
 

duraleigh

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AS a guideline, the forum suggests it is perfectly safe to swim in a pool that is within the values posted in the FC/CYA table.

In other words, if your CYA was 20pp, it is safe to swim in 10ppm FC

If your CYA is 55, it is safe to swim in FC 20-24ppm

This is simply a guideline. Some may be comfortable swimming at higher levels, others may not.
 

lightingguy

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Jun 17, 2010
513
Glendale, CA
At high CYA levels most of the FC is held back in reserve.

It shows up in the test because as the reagent uses up the FC the CYA releases more and more until it's all gone.


A pool with FC of 20 and a CYA of 50 actually has significantly less active HoCl in the water than does a pool with 4ppm FC and no CYA.

You can be reminded why you and I were both poor chemistry students here : pool-water-chemistry-t628.html
 

JasonLion

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May 7, 2007
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If you are testing FC/CC by 0.2s, you want CC to be 0.2 or lower. We don't recommend testing by 0.2s, because that level of precision is not needed and it uses up test reagent more quickly, which is why we normally say that CC should be 0.5 or lower. But if you are actually doing the test by 0.2s then you want CC to be 0.2 or lower.

You are getting CC because your FC level is too low. With CYA around 55, you want FC between 4 and 9, and never below 4. If you raise your FC level up to around 9 the CC should go away. If CC doesn't come down in the next 24 hours, you should shock the pool.
 

Yellowbug33

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Jun 2, 2010
42
I want to make sure I get this right. To shock and with a CYA being 55 then I would have to get the FC up to approx. 22ppm according to the Chlorine/CYA Chart. Every hour last night I went out and put in 1/2 gallon of 12.5% liquid chlorine. Then early this morning I added 2 gallon 1 hour apart. How long should I wait to test. I tested after each hour and before I added more chlorine.
Readings last night, approx. 1 hour apart: 4.5, 8.5, 13.5 and early this am it read 10ppm. I then added one gallon and 1 hour later one more gallon. So now 2 1/2 hours after last chlorine addition it reads:18.5ppm FC and CC was very, very light pink but i had to still add one drop to get it clear and these readings are all with the 10ml sample. It is still cloudy here so should I add another gallon of chlorine? I also thought to shock and get to the breakpoint the FC is raised to ten times the CC. At least that is what the Taylor booklet states. It gets frustrating as stupid me, wanted to double check with a pool store and ever since they had me add to raise my Cal. Hardness and Stabilizer it has been eating chlorine. Then I take it the 3 1/2 inches of rain raised my TA? I also have not been putting any pucks in my skimmer. Just to mention, i have clear water which feels great, no algae problem that I can see and no chlorine smell as you walk around the pool. Everything looks fine but it started eating chlorine and the CC was going up as you can see from my original post. Thanks
 

JasonLion

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The entire breakpoint story is a myth, just ignore that 10 times rule.

Calcium hardness has no effect on chlorine consumption either way.

Stabilizer doesn't eat chlorine. Higher stabilizer (CYA) levels make it more difficult to get rid of algae. It is the algae that "eats" the chlorine. At higher CYA levels it is possible to have algae even without any algae being obviously visible.

Adding chlorine, waiting an hour with the pump running, testing the FC level, and adding more chlorine to get back to shock level is the correct approach. You don't have to do that every hour, though that does speed up the process.

Sunlight helps get rid of CC, so the last bit of CC will probably go away today.

If I am following your description correctly, you were losing a significant amount of chlorine between tests last night? Losing chlorine after sunset means some kind of organic contamination, most likely algae. If so, you need to continue shocking until your overnight FC loss is 1.0 or lower.
 

Yellowbug33

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Jun 2, 2010
42
Do I continue shocking in the day time or wait until tonight? Am I looking to get the FC level to the 22ppm level per the chart with a cya of 55? Thanks
 

Yellowbug33

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Jun 2, 2010
42
Readings of FC Sat. evening each after adding liquid chlorine every hour:
4.5, 8.5, 13.5 and early Sunday am it read 10ppm.
1 hour later one more gallon. So now 2 1/2 hours after last chlorine addition it reads:FC 18.5ppm at approx.8am. and CC was very, very light pink but i had to still add one drop to get it clear .
Now Sunday at approx. 6am here are my readings:
FC 10ppm
CC 0.2
pH 7.5
TA 130
Cal. Hardness 350
CYA 53
So I never got the FC up to 22 last night and I lost 8.5ppm of FC in a matter of 10 hours. It turned out very sunny today and my pool has no shade. I also have not used and chlorine pucks in the skimmer due to CYA.
Can I let the chlorine go to the 5-7ppm as I have guests coming Monday or should I get the FC up to 22 tonight? I did the Pool calculation and have to add 1 1/2 gallons to get it there if the FC is still 10. Thanks
 

lightingguy

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Jun 17, 2010
513
Glendale, CA
Hey Yellow - the timeline is kinda hard to follow. Can you post the total amount of chlorine added Sat, Sun, Mon and just the Evening and Morning FC readings. That might help streamline the process.

Loosing 8.5ppm of chlorine in a day and 3.5ppm overnight would certainly suggest something is using up the chlorine in your pool - algae, etc.
 

benavidescj

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Apr 27, 2010
431
Fleming Island, FL
Yellowbug, the key to shocking is to maintain the shock level. It sounds like you shock and then walk away and let it drop down low again. In the beginning of the shock process you will need to shock to 22 and test often (not 10 hours later) to ensure the FC level stays there. Over time it will stabilize as the organics are killed off. The more you let it drop below shock level the longer this process is going to take.
 

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