Any pool with CYA of 140 ppm would require 14 ppm of FC

czechmate

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Jul 26, 2009
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Split off of CYA too HIGH?. JasonLion

Richard320 said:
70 is quite usable. If you get a lot of direct sun, it's probably good.

Initially you'll need more bleach to get the FC up to the higher level, but daily consumption won't really be any different than if you had 40 ppm. My pool is doing fine despite being stuck with 140 ppm CYA.

You'll have to use the powder and drops to test instead of the color matching, that's all.
It is my understanding, that any pool with CYA of 140 ppm would require 14 ppm of FC, just to keep algae from getting started.
At least that is considered common knowledge among thousands of pool owners and pool service people. 10% of CYA = needed FC. 14 ppm of chlorine is about 4 times the recommended level for people, especially kids should swim in. So your pool may be doing fine, but the human body, which absorbs the chlorine through the skin may not be doing as well.
 

Richard320

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Re: CYA too HIGH?

czechmate said:
It is my understanding, that any pool with CYA of 140 ppm would require 14 ppm of FC, just to keep algae from getting started.
At least that is considered common knowledge among thousands of pool owners and pool service people. 10% of CYA = needed FC. 14 ppm of chlorine is about 4 times the recommended level for people, especially kids should swim in. So your pool may be doing fine, but the human body, which absorbs the chlorine through the skin may not be doing as well.
Do you have any sources other than "common knowledge among thousands of pool owners and pool service people" or your own understanding?

Because it is my understanding that 14ppm with CYA 140 has the same reactivity, for lack of a better technical term as , say, 3 ppm and no CYA. I soaked in it, didn't shower, swam in it the next day, didn't shower for hours afterwards, and felt no dry skin. No rashes.

I even did a little googling. Found this:
3.1 Chlorine
The toxicity literature for chlorine has been comprehensively summarized elsewhere (ACGIH,
1996a; USEPA, 1994a; WHO, 1996; WHO, 2000). According to the latest review by WHO
(2000) related to drinking water, “evidence from these [discussed elsewhere in its report]
animal and human studies suggest that chlorine, hypochlorite solutions, chloramine, and
chlorine dioxide themselves probably do not contribute to the development of cancer or any
toxic effects.” The following briefly describes the chlorine data determined to be particularly
germane to the estimation of the health safety and risk from exposures to chlorine for
swimmers in residential and commercial pools.
3.1.1 Skin Contact
No human or laboratory animal studies were located regarding dermal exposures to chlorine.
However, limited human experiences suggest that chlorine may be capable of causing “itching”
at concentrations much greater than 10 ppm (a case report of a skin patch test of an individual
who was exposed to 400 to 600 ppm of sodium hypochlorite and who was shown to have skin
irritation as a result; a report of an occupational exposure to sodium hypochlorite
(concentration unspecified) causing dermatitis; and a secondary reference stating that 5%-10%
available chlorine is allegedly classified in Europe as an "irritant" whereas <5% does not
require classification as to irritancy). This information has not been confirmed. Because
some microbes present in pool water are known to be stimuli for itching, it is unclear what, if
any, role chlorine might have in this phenomenon.
http://www.waterandhealth.org/pool_spa/hrpool.pdf
 

duraleigh

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Re: CYA too HIGH?

I'll let some folks smarter than me address the "chlorine through the skin" deal but I can address....

It is my understanding, that any pool with CYA of 140 ppm would require 14 ppm of FC, just to keep algae from getting started.
At least that is considered common knowledge among thousands of pool owners and pool service people.
I don't think that is "common" knowledge.

Probably 70% of the complaints of pool water quality on this forum are from people that do not maintain the FC/CYA ratio because they don't know it or understand it. Most of those people have been taking advice from pool service people or pool store employees
 

chem geek

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Re: CYA too HIGH?

czechmate said:
It is my understanding, that any pool with CYA of 140 ppm would require 14 ppm of FC, just to keep algae from getting started.
At least that is considered common knowledge among thousands of pool owners and pool service people. 10% of CYA = needed FC. 14 ppm of chlorine is about 4 times the recommended level for people, especially kids should swim in. So your pool may be doing fine, but the human body, which absorbs the chlorine through the skin may not be doing as well.
As Dave noted, the chlorine/CYA relationship is not common knowledge -- most pool stores and pool service people follow what the industry tells them which is essentially that CYA levels don't matter and that 1-3 ppm FC is all that is needed. This is why there are often so many problems with algae, leading to additional sales of algae-prevention products and systems and of chlorine shock.

Most of the chlorine in a pool with CYA is bound to CYA in a series of compounds called chlorinated isocyanurates. CYA has minimal skin absorption as described here so it is very unlikely that chlorine bound to CYA absorbs through the skin. Hypochlorous acid is the active form of chlorine and it is what oxidizes skin and hair and can have some absorption though it is rather limited because it tends to combine with nitrogenous compounds in your surface skin cells long before it gets very far into your body. Nevertheless, when the FC is around 10% of the CYA level, the hypochlorous acid concentration is roughly the same as found with 0.1 ppm FC and no CYA so it is very, very low -- far lower than found in most tap water or in indoor pools that do not use CYA.

Where are you getting your information? Do you have scientific papers or other credible references you can link to? There is so much baloney in this industry that we try and sift through that and get to the truth by looking at credible sources plus some experiments done by members of this forum.

Richard
 

czechmate

Member
Jul 26, 2009
5
Where am I getting my information??
From your own chart in this forum posted on March 28, 2007. As far as those" thousands of people" is also your own direct quote. used more than once.
It is also very interesting to me that all "chlorine shock" packets contain warnings, indicating when is it save to enter pool.I wander why. It is for example not recommended to swim same day after 4 pounds of 73% Calcium Hypochlorite was put in 20 000 gal pool. Why if it is harmless and tied to CYA? Or how fast does it make that reaction? To me, swimming for hours in a 15ppm of FC (that is free chlorine, not tied to anything), is not only very expensive but also unwise. I will not even go to calculate the amounts needed to shock a pool with 140 ppm of CYA. 60 ppm of FC sustained? So far no flags? Give me a break.
 

bk406

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Dec 3, 2009
2,690
Central Massachusetts
Re: CYA too HIGH?

chem geek said:
when the FC is around 10% of the CYA level, the hypochlorous acid concentration is roughly the same as found with 0.1 ppm FC and no CYA so it is very, very low -- far lower than found in most tap water or in indoor pools that do not use CYA.
This is why you can swim in an FC of 14 ppm if the CYA is 140 ppm. When the FC is bound to CYA, the equalibrium is shifted towards the bound FC-isocyanurates. The net effect is a very low FC thats actually available in the pool.

also, FC used in this context is a bit of a misnomer. Free chlorine in terms of chlorine thats either 1) available in the pool, or 2) chlorine that is bound to CYA. In these cases, the use of the term free chlorine describes both circumstances. This is in contrast to combinded chlorine which describes chlorine bound to nitrogen containing compounds such as swimmer waste.

The warning labels on bags of cal-hypo, dichlor, etc, do not take into account the FC/CYA relationship.

czechmate said:
I will not even go to calculate the amounts needed to shock a pool with 140 ppm of CYA. 60 ppm of FC sustained? So far no flags? Give me a break.
Yes, you are correct. This is why people with pools that have very high CYA levels have an extremely difficult time clearing algea from their pool. The shock level is so high, they never get an FC level high enough to kill the algea.
 

czechmate

Member
Jul 26, 2009
5
Hmmmm, I was under impression, that FC means free chlorine. Not bound to anything, so it is available to atack algae. The one bound to CYA will not be killing it. So it will be harmful to living organism like algae, but humans are absolutely immune to it, because we have a fancy chemical names for it?
Interesting.
 

bk406

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Dec 3, 2009
2,690
Central Massachusetts
czechmate said:
So it will be harmful to living organism like algae, but humans are absolutely immune to it, because we have a fancy chemical names for it?
Interesting.
I'm not sure I understand what you are saying. Chlorine bound to the CYA is inactive, but is still refered to as FC. Yes, an active FC of 1-3 ppm will kill most if not all pathogens present in the pool and will handle the algea as well. This level is not harmful to humans. What Chemgeek is explaining is that if the FC is 7-10% of the CYA level, it has the net effect of being in the 1-3 ppm range, no matter what the actual FC reading is on a test. As unbound FC is consumed, CYA bound FC then disscociates and keeps the equilibrium balanced. I'm not sure what the Equ constant is, but i bet chemgeek knows.
The science is solid. Not sure what you mean by fancy chemical names either. It's science, not alchemy. :wink:
 

JasonLion

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An FC level of 14, with a CYA level of zero, will cause some minor problems. The most obvious is that hair tends to suffer damage at FC levels above 3, with the rate of damage increasing as the FC level rises. However as soon as CYA enters the picture the whole situation changes.
 

chem geek

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czechmate said:
Where am I getting my information??
From your own chart in this forum posted on March 28, 2007. As far as those" thousands of people" is also your own direct quote. used more than once.
It is also very interesting to me that all "chlorine shock" packets contain warnings, indicating when is it save to enter pool.I wander why. It is for example not recommended to swim same day after 4 pounds of 73% Calcium Hypochlorite was put in 20 000 gal pool. Why if it is harmless and tied to CYA? Or how fast does it make that reaction?
For sources of information, I wasn't talking about having a high FC needed at higher CYA to prevent algae growth (i.e. the chlorine/CYA chart). As for the thousands of people, I was referring to the tens of thousands at TFP and other pool forums that follow the chlorine/CYA principles, but there are around 8 million pools in the U.S. so this is a drop in the bucket and does not represent what most people are doing and certainly does not represent what the pool industry says to do -- I'm sorry for that confusion. When I asked about where you got your information, I should have explicitly said that my question was about your statement: "So your pool may be doing fine, but the human body, which absorbs the chlorine through the skin may not be doing as well." You made several assumptions here: 1) that FC measures the active chlorine level, which it does not and 2) that the chlorine (in whatever form) absorbs through the skin, which it does not (at least not for CYA and most likely not for chlorine bound to CYA).

The chlorine/CYA relationship has been known in detail since at least 1974 as described in this scientific paper. Note that what is referred to in this paper as "free chlorine" in those days is unbound, but that these days FC refers to what is measured in chlorine tests and that includes the chlorine bound to CYA because it releases from CYA in the timeframe of the test. So in the terminology of the paper, the chlorine test measures reservoir chlorine. Essentially, there is a chemical pathway that has half of the chlorine bound to CYA get converted to hypochlorous acid every 1/4 second (see this EPA document on document page 12, PDF file page 18). Since the FC test takes more than a few seconds, it essentially measures reservoir chlorine which is mostly the chlorine bound to CYA. That is, it measures the chlorine capacity or reserve.

As for the label warnings, these are regulated by the EPA with what are known as FIFRA rules that apply to all pesticides. The EPA sets a maximum chlorine exposure level of 4 ppm based on drinking water standards. They did not adjust this for CYA and besides, the chlorine manufacturers don't know if you have any CYA in the water so would have to use the worst-case scenario which is not having any CYA at all unless they were to have far more complex labeling and get the EPA to understand the chlorine/CYA relationship.

Richard
 

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