I have a question related to the chlorine/cya topic as I understand the interaction between the two and in relationship to sanitation of pool water along with the other guys ph ta etc, but my question is when it comes to the physical exposure of chlorine concentrations in relationship to the human body health and safety beyond sanitation is it not just the total fc chlorine that we should consider and not the cya activity that only relates to sanitation. I am referring to physical contact, absorption, ingesting/swallowing high concentrations regardless of the cya formula. Like I tested my 10500 gal pool and I have 3ppm but given my cya of 90, I should raise my chlorine level to 7ppm because my cya is too high and affecting my chlorine from attacking and becoming chloramines but I still have that chlorine in my pool and it still will come in contact with the swimmer right so then in reality it's 7ppm not 3ppm exposure to a swimmer, right? So I see two measurements which are conflicting if true; one is sanitation and the other is swimmer safety from exposure to chemicals. What is your take on this as I really want to know and I'm sure some people have health conditions that need to know too. Another way to look at it is they say under 10ppm is the limit to swim safely but should we only consider the "active" chlorine based on the cya calculations or all FC the Taylor testing shows?
CYA/FC PPM Chemistry levels vs Physical swimmer safety standards FC ppm limits
- Thread starter Drd
- Start date
No, actually the 7ppm is after it's been released from the CYA. In your pool, it equated to like 0.1ppm chlorine that the swimmers are exposed to. Took me a little while to understand that. When you do the FC test, it forces the chlorine to be released from the CYA bondage. That's why we can say that it's safe all the way up to shock level for a given CYA. The actual active chlorine is much less than most folks are exposed to at a commercial pool.
- May 23, 2015
- 24,711
- Pool Size
- 16000
- Surface
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- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Free chlorine is a measure of three different chemical species - hypochlorous acid (HOCl), hypochlorite anion (OCl-) and chlorine bound to CYA (chlorinated cyanurate). When you do the DPD-FAS test, the dye reacts with all three components and so you are measuring the sum of all active chlorine species (HOCl/OCl-) as well as the chlorine held in reserve (CYA-Cl).
Chlorine that is bound to CYA is inert - in other words, if there is nothing for it to react with, the chlorine will stay bound to the CYA and it will not do much. Chlorine can be released from CYA as the HOCl/OCl- gets used up in solutions and the reaction rate for chlorine being released is about 0.25 secs. When the FC/CYA ratio is ~7.5% and the pH is ~ 7.5, the active chlorine (HOCl/OCl-) levels in solution are split about evenly and the total concentration of them is 100ppb (0.1ppm). This level of active chlorine is high enough to kill algae and pathogens but low enough to be quite safe. By contrast, water with no CYA in the water, it has ~15X the amount of active chlorine in it than when the FC/CYA ratio is 7.5%.
As for human health effects, they are minimal. There is very little dermal absorption of chlorine through the skin and into the body as you skin is a very effective barrier against the environment. Does the active chlorine react with your skin? Sure. But there is so little of it in solution that it's practically meaningless. The analogy would be a person shooting spitballs at a Sherman tank.
What about ingestion?? Well, first off, no one would suggest drinking pool water. Does some get into your mouth and nose? Yes. But again, the quantities we are talking about are so low that they are insignificant. The human body has plenty of anti-oxidant mechanisms that will neutralize free chlorine inside the body. In fact, one of the kill mechanisms of your immune system is for the immune cells to generate hypochlorous acid in-situ to kill pathogens.
As an aside, hospitals actually use a bleach/water solution for disinfecting difficult to treat wounds that is hundreds of times more concentrated than pool water (YippySkippy can give us the link) and contains no CYA so it is completely unbuffered. Some dermatologists also recommend bleach baths for people with eczema or psoriasis as a way of reducing skin inflammations.
There is simply not enough chlorine in pool water to be at all concerned about human health effects and there is no studies that I am aware of that show any kind of adverse cumulative health effects. I don't have links at hand but considering how much chlorine is used in the treatment of municipal water supplies, I suspect one could easily find thousands of epidemiological studies done by the CDC and EPA regarding the human health effects of chlorine in drinking water.
Chlorine that is bound to CYA is inert - in other words, if there is nothing for it to react with, the chlorine will stay bound to the CYA and it will not do much. Chlorine can be released from CYA as the HOCl/OCl- gets used up in solutions and the reaction rate for chlorine being released is about 0.25 secs. When the FC/CYA ratio is ~7.5% and the pH is ~ 7.5, the active chlorine (HOCl/OCl-) levels in solution are split about evenly and the total concentration of them is 100ppb (0.1ppm). This level of active chlorine is high enough to kill algae and pathogens but low enough to be quite safe. By contrast, water with no CYA in the water, it has ~15X the amount of active chlorine in it than when the FC/CYA ratio is 7.5%.
As for human health effects, they are minimal. There is very little dermal absorption of chlorine through the skin and into the body as you skin is a very effective barrier against the environment. Does the active chlorine react with your skin? Sure. But there is so little of it in solution that it's practically meaningless. The analogy would be a person shooting spitballs at a Sherman tank.
What about ingestion?? Well, first off, no one would suggest drinking pool water. Does some get into your mouth and nose? Yes. But again, the quantities we are talking about are so low that they are insignificant. The human body has plenty of anti-oxidant mechanisms that will neutralize free chlorine inside the body. In fact, one of the kill mechanisms of your immune system is for the immune cells to generate hypochlorous acid in-situ to kill pathogens.
As an aside, hospitals actually use a bleach/water solution for disinfecting difficult to treat wounds that is hundreds of times more concentrated than pool water (YippySkippy can give us the link) and contains no CYA so it is completely unbuffered. Some dermatologists also recommend bleach baths for people with eczema or psoriasis as a way of reducing skin inflammations.
There is simply not enough chlorine in pool water to be at all concerned about human health effects and there is no studies that I am aware of that show any kind of adverse cumulative health effects. I don't have links at hand but considering how much chlorine is used in the treatment of municipal water supplies, I suspect one could easily find thousands of epidemiological studies done by the CDC and EPA regarding the human health effects of chlorine in drinking water.
I am overwelmed by the detailed response to this question, thank you so much! I will print this out and put it in my pool information book I have created to keep important stuff ...I feel so much better now, as I am newbe to taking care of my pool myself (using a liquid chlorine feeder attached to my pump system) and a bit nervous I'm doing things right. I haven't heard anything here about making sure you use something to protect yourself from the chlorine fumes which are quite strong at 12.5% strength recommended and as soon as you open the cap, its overwhelming. I bought a chemical respirator N95 rated mask to wear and protective glasses and gloves (even the test kits has some pretty hazzardess chemicals in it). Maybe it's discussed somewhere I haven't visited as of yet, but I highly recommend it. I do feel much better understanding knowing the higher FC level I am maintaining due to cya in my pool is safe health wise as well sanitation wise.....I have an upper respiratory condition and need to be watchful as well as responsible of others that enter my pool. Again thank you!
I can't really add to what Matt posted beyond providing a link to a chart that will allow you to compare the "active" FC levels as a function of CYA and FC. Looking at this chart created by Chem Geek allows you to better understand the active chlorine levels.
http://troublefreepool.com/~richardfalk/pool/HOCl.htm
Just compare the value of a non-stabilized pool with 2ppm of FC (think indoor YMCA) {0.967} to our recommendation of 30ppm of CYA with a 5ppm CYA {0.078} ...
That "YMCA" pool is 12x harsher than the TFP pool.
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I have never smelled any fumes coming out of the 12.5% bleach bottles.
And I HIGHLY!!! recommend you NOT use the respirator when handling muriatic acid as your nose is your best early warning system.
http://troublefreepool.com/~richardfalk/pool/HOCl.htm
Just compare the value of a non-stabilized pool with 2ppm of FC (think indoor YMCA) {0.967} to our recommendation of 30ppm of CYA with a 5ppm CYA {0.078} ...
That "YMCA" pool is 12x harsher than the TFP pool.
- - - Updated - - -
I have never smelled any fumes coming out of the 12.5% bleach bottles.
And I HIGHLY!!! recommend you NOT use the respirator when handling muriatic acid as your nose is your best early warning system.
I think your responses should be documented in the pool school because this is very useful information others really need to know that are embarking on the TFP methods of pool care. 
I think your responses should be documented in the pool school because this is very useful information others really need to know that are embarking on the TFP methods of pool care.
I found this information on handling of pool chemical hazards which is very informative;
http://blog.poolcenter.com/article.aspx?articleid=6532
I found this on another thread:
christianday wrote "Got a great 3M vapor mask with cartridges specifically designed to filter acid fumes and the googles to match. This was the first time I could not smell that horrid stuff and now I feel a little better using it
This is the 3M 60923 filter to use. They had a mask at Lowes with those cartridges in it but I can't seem to find it on their site to link. But the filters are pretty interchangeable with the masks from what I could see."
This is not for the tough guys out there
- May 23, 2015
- 24,711
- Pool Size
- 16000
- Surface
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- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
You really should heed the advice here and NOT use a chemical filter. Unless you are properly fitted for a full face SCBA mask, you run the very serious risk of exposing parts of your face (i.e., your eyes) to acid vapors without any recoil reflex response that comes from when your nose detects the vapors.
Muriatic acid vapors ARE NOT hazardous in an outdoor environment. The odor threshold for MA vapors is well below any toxicity limit. In other words, when you smell acid vapors, your nose is detecting them well before you will ever experience any harmful effects. Bleach is exactly the same way - you will smell it well before it is ever harmful to you.
I worked for 14 years in an industrial chemical setting and have had as many years of OSHA-approved Industrial Hygiene & Safety courses. I can tell you emphatically that the old wives tales and urban legends that people throw around about pool chemicals is just that - a lot of B/S and very little substantive facts. As long as you exercise a modicum of common sense while handling these chemicals, e.g., wearing protective eyewear, staying up wind when pouring, pouring slowly from a bottle with minimal distance to the water, etc, you will be perfectly fine.
Muriatic acid vapors ARE NOT hazardous in an outdoor environment. The odor threshold for MA vapors is well below any toxicity limit. In other words, when you smell acid vapors, your nose is detecting them well before you will ever experience any harmful effects. Bleach is exactly the same way - you will smell it well before it is ever harmful to you.
I worked for 14 years in an industrial chemical setting and have had as many years of OSHA-approved Industrial Hygiene & Safety courses. I can tell you emphatically that the old wives tales and urban legends that people throw around about pool chemicals is just that - a lot of B/S and very little substantive facts. As long as you exercise a modicum of common sense while handling these chemicals, e.g., wearing protective eyewear, staying up wind when pouring, pouring slowly from a bottle with minimal distance to the water, etc, you will be perfectly fine.
We did see a report here that someone was using a respirator and safety glasses while using acid and their eyes were burnt from the acid fumes. They couldn't detect that they were being exposed to acid fumes due to the respirator and their eyes were exposed to the fumes and were damaged.
As Matt has suggested, the nose is the best detection of fumes and you will instantly get out of any fumes if you smell them. If you can't smell them due to a respirator, they are still there and doing damage to the eyes.
As Matt has suggested, the nose is the best detection of fumes and you will instantly get out of any fumes if you smell them. If you can't smell them due to a respirator, they are still there and doing damage to the eyes.
Oly
Gold Supporter
Red numbers - not enough active cl2 to kill bacteria
Green numbers - not enough active cl2 to prevent algae growth
Blue numbers - safe to swim!
Oly
Gold Supporter
I disagree a bit on the blue ... you going to swim in 100ppm FC with CYA = 0?
Blue basically I think will kill bacteria and algae, but says nothing about it getting too high to swim.
I would just ignore the colors.
I simply pulled that information from Chem Geeks post: https://www.troublefreepool.com/threads/558-Pool-Water-Chemistry
"So, red means bacterial growth while green means possible algae growth. Blue is the safe area."
Red is unsanitary
Green is sanitary and where algae starts to be killed faster than it can reproduce. It is the equivalent of about 0.1 ppm unstabilized FC.
Blue is where you start getting in to SLAM ranges and above.
While this chart is helpful to illustrate how CYA buffers chlorine, it is best to stick to the FC/CYA ratio charts here. As Jason said, the colors aren't important, the numbers are.
Green is sanitary and where algae starts to be killed faster than it can reproduce. It is the equivalent of about 0.1 ppm unstabilized FC.
Blue is where you start getting in to SLAM ranges and above.
While this chart is helpful to illustrate how CYA buffers chlorine, it is best to stick to the FC/CYA ratio charts here. As Jason said, the colors aren't important, the numbers are.
Ah, thanks! Seems like there should be another color ... Do Not Enter (Which I would think is up around a value of 2 or so)
(Which I would think is up around a value of 2 or so)Ah, thanks! Seems like there should be another color ... Do Not Enter
Yeah, I agree with that. I'm sure Chem Geek was saying "Safe" in that no algae or bacteria was going to live for very long. Of course, at some of those ridiculously high numbers people might not either!
